[U-Boot] [PATCH] kconfiglib: update to the latest version

Ulf Magnusson ulfalizer at gmail.com
Fri Jun 12 18:56:19 CEST 2015


Corresponds to 2f319b8 in https://github.com/ulfalizer/Kconfiglib.

Fixes:

  - Unset user values when loading a zero-byte .config. (5e54e2c)
  - Ignore indented .config assignments. (f8a7510)
  - Do not require $srctree to be set for non-kernel projects. (d56e9c1)

Also adds Python 3 support and has a lot of internal cleanup and
optimization. Makes tools/genboardscfg.py run slightly faster.

Signed-off-by: Ulf Magnusson <ulfalizer at gmail.com>
---
 tools/buildman/kconfiglib.py | 2898 +++++++++++++++++++-----------------------
 1 file changed, 1329 insertions(+), 1569 deletions(-)

diff --git a/tools/buildman/kconfiglib.py b/tools/buildman/kconfiglib.py
index 655cf44..e71f43e 100644
--- a/tools/buildman/kconfiglib.py
+++ b/tools/buildman/kconfiglib.py
@@ -36,57 +36,61 @@ Kconfig-based configuration systems. Features include the following:
 
 For the Linux kernel, scripts are run using
 
- $ make scriptconfig SCRIPT=<path to script> [SCRIPT_ARG=<arg>]
+ $ make scriptconfig [ARCH=<arch>] SCRIPT=<path to script> [SCRIPT_ARG=<arg>]
 
-Running scripts via the 'scriptconfig' target ensures that required environment
-variables (SRCARCH, ARCH, srctree, KERNELVERSION, etc.) are set up correctly.
-Alternative architectures can be specified like for other 'make *config'
-targets:
+Using the 'scriptconfig' target ensures that required environment variables
+(SRCARCH, ARCH, srctree, KERNELVERSION, etc.) are set up correctly.
 
- $ make scriptconfig ARCH=mips SCRIPT=<path to script> [SCRIPT_ARG=<arg>]
-
-The script will receive the name of the Kconfig file to load in sys.argv[1].
-(As of Linux 3.7.0-rc8 this is always "Kconfig" from the kernel top-level
-directory.) If an argument is provided with SCRIPT_ARG, it will appear in
-sys.argv[2].
+Scripts receive the name of the Kconfig file to load in sys.argv[1]. As of
+Linux 4.1.0-rc5, this is always "Kconfig" from the kernel top-level directory.
+If an argument is provided with SCRIPT_ARG, it appears as sys.argv[2].
 
 To get an interactive Python prompt with Kconfiglib preloaded and a Config
-object 'c' created, use
+object 'c' created, run
 
- $ make iscriptconfig [ARCH=<architecture>]
+ $ make iscriptconfig [ARCH=<arch>]
 
-Kconfiglib requires Python 2. For (i)scriptconfig the command to run the Python
-interpreter can be passed in the environment variable PYTHONCMD (defaults to
-'python'; PyPy works too and is a bit faster).
+Kconfiglib supports both Python 2 and Python 3. For (i)scriptconfig, the Python
+interpreter to use can be passed in PYTHONCMD, which defaults to 'python'. PyPy
+works well too, and might give a nice speedup for long-running jobs.
 
-Look in the examples/ subdirectory for examples, which can be run with e.g.
+The examples/ directory contains short example scripts, which can be run with
+e.g.
 
  $ make scriptconfig SCRIPT=Kconfiglib/examples/print_tree.py
 
 or
 
- $ make scriptconfig SCRIPT=Kconfiglib/examples/help_grep.py SCRIPT_ARG="kernel"
+ $ make scriptconfig SCRIPT=Kconfiglib/examples/help_grep.py SCRIPT_ARG=kernel
 
-Look in testsuite.py for the test suite.
+testsuite.py contains the test suite. See the top of the script for how to run
+it.
 
 Credits: Written by Ulf "Ulfalizer" Magnusson
 
-Send bug reports, suggestions and other feedback to kconfiglib at gmail.com .
-Don't wrestle with internal APIs. Tell me what you need and I might add it in a
-safe way as a client API instead."""
-
-# If you have Psyco installed (32-bit installations, Python <= 2.6 only),
-# setting this to True (right here, not at runtime) might give a nice speedup.
-# (22% faster for parsing arch/x86/Kconfig and 58% faster for evaluating all
-# symbols in it without a .config on my Core Duo.)
-use_psyco = False
+Send bug reports, suggestions and other feedback to ulfalizer a.t Google's
+email service. Don't wrestle with internal APIs. Tell me what you need and I
+might add it in a safe way as a client API instead."""
 
 import os
 import re
-import string
 import sys
 
-class Config():
+# File layout:
+#
+# Public classes
+# Public functions
+# Internal classes
+# Internal functions
+# Internal global constants
+
+# Line length: 79 columns
+
+#
+# Public classes
+#
+
+class Config(object):
 
     """Represents a Kconfig configuration, e.g. for i386 or ARM. This is the
     set of symbols and other items appearing in the configuration together with
@@ -97,31 +101,30 @@ class Config():
     # Public interface
     #
 
-    def __init__(self,
-                 filename = "Kconfig",
-                 base_dir = "$srctree",
-                 print_warnings = True,
-                 print_undef_assign = False):
+    def __init__(self, filename="Kconfig", base_dir=None, print_warnings=True,
+                 print_undef_assign=False):
         """Creates a new Config object, representing a Kconfig configuration.
         Raises Kconfig_Syntax_Error on syntax errors.
 
         filename (default: "Kconfig") -- The base Kconfig file of the
-                 configuration. For the Linux kernel, this should usually be be
+                 configuration. For the Linux kernel, you'll probably want
                  "Kconfig" from the top-level directory, as environment
                  variables will make sure the right Kconfig is included from
-                 there (usually arch/<architecture>/Kconfig). If you are using
-                 kconfiglib via 'make scriptconfig' the filename of the
-                 correct Kconfig will be in sys.argv[1].
-
-        base_dir (default: "$srctree") -- The base directory relative to which
-                'source' statements within Kconfig files will work. For the
-                Linux kernel this should be the top-level directory of the
-                kernel tree. $-references to environment variables will be
-                expanded.
-
-                The environment variable 'srctree' is set by the Linux makefiles
-                to the top-level kernel directory. A default of "." would not
-                work if an alternative build directory is used.
+                 there (arch/<architecture>/Kconfig). If you are using
+                 kconfiglib via 'make scriptconfig', the filename of the base
+                 base Kconfig file will be in sys.argv[1].
+
+        base_dir (default: None) -- The base directory relative to which
+                 'source' statements within Kconfig files will work. For the
+                 Linux kernel this should be the top-level directory of the
+                 kernel tree. $-references to existing environment variables
+                 will be expanded.
+
+                 If None (the default), the environment variable 'srctree' will
+                 be used if set, and the current directory otherwise. 'srctree'
+                 is set by the Linux makefiles to the top-level kernel
+                 directory. A default of "." would not work with an alternative
+                 build directory.
 
         print_warnings (default: True) -- Set to True if warnings related to
                        this configuration should be printed to stderr. This can
@@ -138,6 +141,12 @@ class Config():
         # The set of all symbols, indexed by name (a string)
         self.syms = {}
 
+        # Python 2/3 compatibility hack. This is the only one needed.
+        if sys.version_info[0] >= 3:
+            self.syms_iter = self.syms.values
+        else:
+            self.syms_iter = self.syms.itervalues
+
         # The set of all defined symbols in the configuration in the order they
         # appear in the Kconfig files. This excludes the special symbols n, m,
         # and y as well as symbols that are referenced but never defined.
@@ -147,14 +156,14 @@ class Config():
         # by name (a string)
         self.named_choices = {}
 
-        def register_special_symbol(type, name, value):
+        def register_special_symbol(type_, name, val):
             sym = Symbol()
             sym.is_special_ = True
             sym.is_defined_ = True
             sym.config = self
             sym.name = name
-            sym.type = type
-            sym.cached_value = value
+            sym.type = type_
+            sym.cached_val = val
             self.syms[name] = sym
             return sym
 
@@ -172,7 +181,7 @@ class Config():
         self.defconfig_sym = None
 
         # See Symbol.get_(src)arch()
-        self.arch    = os.environ.get("ARCH")
+        self.arch = os.environ.get("ARCH")
         self.srcarch = os.environ.get("SRCARCH")
 
         # See Config.__init__(). We need this for get_defconfig_filename().
@@ -181,7 +190,10 @@ class Config():
             self.srctree = "."
 
         self.filename = filename
-        self.base_dir = _strip_trailing_slash(os.path.expandvars(base_dir))
+        if base_dir is None:
+            self.base_dir = self.srctree
+        else:
+            self.base_dir = os.path.expandvars(base_dir)
 
         # The 'mainmenu' text
         self.mainmenu_text = None
@@ -210,11 +222,11 @@ class Config():
         self.end_line_tokens = None
 
         # See the comment in _parse_expr().
-        self.parse_expr_cur_sym_or_choice = None
-        self.parse_expr_line = None
-        self.parse_expr_filename = None
-        self.parse_expr_linenr = None
-        self.parse_expr_transform_m = None
+        self._cur_item = None
+        self._line = None
+        self._filename = None
+        self._linenr = None
+        self._transform_m = None
 
         # Parse the Kconfig files
         self.top_block = self._parse_file(filename, None, None, None)
@@ -222,148 +234,144 @@ class Config():
         # Build Symbol.dep for all symbols
         self._build_dep()
 
-    def load_config(self, filename, replace = True):
+    def load_config(self, filename, replace=True):
         """Loads symbol values from a file in the familiar .config format.
-           Equivalent to calling Symbol.set_user_value() to set each of the
-           values.
-
-           filename -- The .config file to load. $-references to environment
-                       variables will be expanded. For scripts to work even
-                       when an alternative build directory is used with the
-                       Linux kernel, you need to refer to the top-level kernel
-                       directory with "$srctree".
+        Equivalent to calling Symbol.set_user_value() to set each of the
+        values.
 
-           replace (default: True) -- True if the configuration should replace
-                   the old configuration; False if it should add to it."""
+        "# CONFIG_FOO is not set" within a .config file is treated specially
+        and sets the user value of FOO to 'n'. The C implementation works the
+        same way.
 
-        def warn_override(filename, linenr, name, old_user_val, new_user_val):
-            self._warn("overriding the value of {0}. "
-                       'Old value: "{1}", new value: "{2}".'
-                        .format(name, old_user_val, new_user_val),
-                       filename,
-                       linenr)
+        filename -- The .config file to load. $-references to environment
+                    variables will be expanded. For scripts to work even when
+                    an alternative build directory is used with the Linux
+                    kernel, you need to refer to the top-level kernel directory
+                    with "$srctree".
 
-        filename = os.path.expandvars(filename)
+        replace (default: True) -- True if the configuration should replace
+                the old configuration; False if it should add to it."""
 
         # Put this first so that a missing file doesn't screw up our state
-        line_feeder = _FileFeed(_get_lines(filename), filename)
+        filename = os.path.expandvars(filename)
+        line_feeder = _FileFeed(filename)
 
         self.config_filename = filename
 
-        # Invalidate everything. This is usually faster than finding the
-        # minimal set of symbols that needs to be invalidated, as nearly all
-        # symbols will tend to be affected anyway.
-        if replace:
-            self.unset_user_values()
-        else:
-            self._invalidate_all()
-
+        #
         # Read header
-
-        self.config_header = None
+        #
 
         def is_header_line(line):
-            return line.startswith("#") and \
-                   not unset_re.match(line)
-
-        first_line = line_feeder.get_next()
-
-        if first_line is None:
-            return
-
-        if not is_header_line(first_line):
-            line_feeder.go_back()
-        else:
-            self.config_header = first_line[1:]
+            return line is not None and line.startswith("#") and \
+                   not _unset_re_match(line)
 
-            # Read remaining header lines
-            while 1:
-                line = line_feeder.get_next()
-
-                if line is None:
-                    break
-
-                if not is_header_line(line):
-                    line_feeder.go_back()
-                    break
-
-                self.config_header += line[1:]
+        self.config_header = None
 
+        line = line_feeder.peek_next()
+        if is_header_line(line):
+            self.config_header = ""
+            while is_header_line(line_feeder.peek_next()):
+                self.config_header += line_feeder.get_next()[1:]
             # Remove trailing newline
             if self.config_header.endswith("\n"):
                 self.config_header = self.config_header[:-1]
 
-        # Read assignments
+        #
+        # Read assignments. Hotspot for some workloads.
+        #
 
-        filename = line_feeder.get_filename()
+        def warn_override(filename, linenr, name, old_user_val, new_user_val):
+            self._warn('overriding the value of {0}. '
+                       'Old value: "{1}", new value: "{2}".'
+                       .format(name, old_user_val, new_user_val),
+                       filename, linenr)
+
+        # Invalidate everything to keep things simple. It might be possible to
+        # improve performance for the case where multiple configurations are
+        # loaded by only invalidating a symbol (and its dependent symbols) if
+        # the new user value differs from the old. One complication would be
+        # that symbols not mentioned in the .config must lose their user value
+        # when replace = True, which is the usual case.
+        if replace:
+            self.unset_user_values()
+        else:
+            self._invalidate_all()
 
         while 1:
             line = line_feeder.get_next()
             if line is None:
                 return
 
-            linenr = line_feeder.get_linenr()
+            line = line.rstrip()
 
-            line = line.strip()
+            set_match = _set_re_match(line)
+            if set_match:
+                name, val = set_match.groups()
+
+                if val.startswith(('"', "'")):
+                    if len(val) < 2 or val[-1] != val[0]:
+                        _parse_error(line, "malformed string literal",
+                                     line_feeder.get_filename(),
+                                     line_feeder.get_linenr())
+                    # Strip quotes and remove escapings. The unescaping
+                    # procedure should be safe since " can only appear as \"
+                    # inside the string.
+                    val = val[1:-1].replace('\\"', '"').replace("\\\\", "\\")
 
-            set_re_match = set_re.match(line)
-            if set_re_match:
-                name, val = set_re_match.groups()
-                # The unescaping producedure below should be safe since " can
-                # only appear as \" inside the string
-                val = _strip_quotes(val, line, filename, linenr)\
-                      .replace('\\"', '"').replace("\\\\", "\\")
                 if name in self.syms:
                     sym = self.syms[name]
-
-                    old_user_val = sym.user_val
-                    if old_user_val is not None:
-                        warn_override(filename, linenr, name, old_user_val, val)
+                    if sym.user_val is not None:
+                        warn_override(line_feeder.get_filename(),
+                                      line_feeder.get_linenr(),
+                                      name, sym.user_val, val)
 
                     if sym.is_choice_symbol_:
                         user_mode = sym.parent.user_mode
                         if user_mode is not None and user_mode != val:
-                            self._warn("assignment to {0} changes mode of containing "
-                                       'choice from "{1}" to "{2}".'
+                            self._warn("assignment to {0} changes mode of "
+                                       'containing choice from "{1}" to "{2}".'
                                        .format(name, val, user_mode),
-                                       filename,
-                                       linenr)
+                                       line_feeder.get_filename(),
+                                       line_feeder.get_linenr())
 
                     sym._set_user_value_no_invalidate(val, True)
-
                 else:
-                    self._undef_assign('attempt to assign the value "{0}" to the '
-                                       "undefined symbol {1}."
-                                       .format(val, name),
-                                       filename,
-                                       linenr)
-
+                    if self.print_undef_assign:
+                        _stderr_msg('note: attempt to assign the value "{0}" '
+                                    "to the undefined symbol {1}."
+                                    .format(val, name),
+                                    line_feeder.get_filename(),
+                                    line_feeder.get_linenr())
             else:
-                unset_re_match = unset_re.match(line)
-                if unset_re_match:
-                    name = unset_re_match.group(1)
+                unset_match = _unset_re_match(line)
+                if unset_match:
+                    name = unset_match.group(1)
                     if name in self.syms:
                         sym = self.syms[name]
-
-                        old_user_val = sym.user_val
-                        if old_user_val is not None:
-                            warn_override(filename, linenr, name, old_user_val, "n")
+                        if sym.user_val is not None:
+                            warn_override(line_feeder.get_filename(),
+                                          line_feeder.get_linenr(),
+                                          name, sym.user_val, "n")
 
                         sym._set_user_value_no_invalidate("n", True)
 
-    def write_config(self, filename, header = None):
+    def write_config(self, filename, header=None):
         """Writes out symbol values in the familiar .config format.
 
-           filename -- The filename under which to save the configuration.
+        Kconfiglib makes sure the format matches what the C implementation
+        would generate, down to whitespace. This eases testing.
+
+        filename -- The filename under which to save the configuration.
 
-           header (default: None) -- A textual header that will appear at the
-                  beginning of the file, with each line commented out
-                  automatically. None means no header."""
+        header (default: None) -- A textual header that will appear at the
+               beginning of the file, with each line commented out
+               automatically. None means no header."""
 
         # already_written is set when _make_conf() is called on a symbol, so
         # that symbols defined in multiple locations only get one entry in the
         # .config. We need to reset it prior to writing out a new .config.
-        for sym in self.syms.itervalues():
+        for sym in self.syms_iter():
             sym.already_written = False
 
         with open(filename, "w") as f:
@@ -373,11 +381,13 @@ class Config():
                 f.write("\n")
 
             # Write configuration.
-            # (You'd think passing a list around to all the nodes and appending
-            # to it to avoid copying would be faster, but it's actually a lot
-            # slower with PyPy, and about as fast with Python. Passing the file
-            # around is slower too.)
-            f.write("\n".join(self.top_block._make_conf()))
+
+            # Passing a list around to all the nodes and appending to it to
+            # avoid copying was surprisingly a lot slower with PyPy, and about
+            # as fast with Python. Passing the file around was slower too. Been
+            # a while since I last measured though.
+
+            f.write("\n".join(_make_block_conf(self.top_block)))
             f.write("\n")
 
     def get_kconfig_filename(self):
@@ -395,8 +405,8 @@ class Config():
     def get_srcarch(self):
         """Returns the value the environment variable SRCARCH had at the time
         the Config instance was created, or None if SRCARCH was not set. For
-        the kernel, this corresponds to the arch/ subdirectory containing
-        architecture-specific source code."""
+        the kernel, this corresponds to the particular arch/ subdirectory
+        containing architecture-specific code."""
         return self.srcarch
 
     def get_srctree(self):
@@ -407,8 +417,8 @@ class Config():
         return self.srctree
 
     def get_config_filename(self):
-        """Returns the name of the most recently loaded configuration file, or
-        None if no configuration has been loaded."""
+        """Returns the filename of the most recently loaded configuration file,
+        or None if no configuration has been loaded."""
         return self.config_filename
 
     def get_mainmenu_text(self):
@@ -429,24 +439,28 @@ class Config():
         If the environment variable 'srctree' was set when the Config was
         created, get_defconfig_filename() will first look relative to that
         directory before looking in the current directory; see
-        Config.__init__()."""
-
+        Config.__init__().
+
+        WARNING: A wart here is that scripts/kconfig/Makefile sometimes uses
+        the --defconfig=<defconfig> option when calling the C implementation of
+        e.g. 'make defconfig'. This option overrides the 'option
+        defconfig_list' symbol, meaning the result from
+        get_defconfig_filename() might not match what 'make defconfig' would
+        use. That probably ought to be worked around somehow, so that this
+        function always gives the "expected" result."""
         if self.defconfig_sym is None:
             return None
-
-        for (filename, cond_expr) in self.defconfig_sym.def_exprs:
+        for filename, cond_expr in self.defconfig_sym.def_exprs:
             if self._eval_expr(cond_expr) == "y":
                 filename = self._expand_sym_refs(filename)
-
                 # We first look in $srctree. os.path.join() won't work here as
                 # an absolute path in filename would override $srctree.
-                srctree_filename = os.path.normpath(self.srctree + "/" + filename)
+                srctree_filename = os.path.normpath(self.srctree + "/" +
+                                                    filename)
                 if os.path.exists(srctree_filename):
                     return srctree_filename
-
                 if os.path.exists(filename):
                     return filename
-
         return None
 
     def get_symbol(self, name):
@@ -457,13 +471,13 @@ class Config():
         return self.syms.get(name)
 
     def get_top_level_items(self):
-        """Returns a list containing the items (symbols, menus, choice
-        statements and comments) at the top level of the configuration -- that
-        is, all items that do not appear within a menu or choice. The items
-        appear in the same order as within the configuration."""
-        return self.top_block.get_items()
+        """Returns a list containing the items (symbols, menus, choices, and
+        comments) at the top level of the configuration -- that is, all items
+        that do not appear within a menu or choice. The items appear in the
+        same order as within the configuration."""
+        return self.top_block
 
-    def get_symbols(self, all_symbols = True):
+    def get_symbols(self, all_symbols=True):
         """Returns a list of symbols from the configuration. An alternative for
         iterating over all defined symbols (in the order of definition) is
 
@@ -475,12 +489,13 @@ class Config():
         for sym in config.get_symbols(False):
             ...
 
-        all_symbols (default: True) -- If True, all symbols - including special
-                    and undefined symbols - will be included in the result, in
-                    an undefined order. If False, only symbols actually defined
-                    and not merely referred to in the configuration will be
-                    included in the result, and will appear in the order that
-                    they are defined within the Kconfig configuration files."""
+        all_symbols (default: True) -- If True, all symbols -- including
+                    special and undefined symbols -- will be included in the
+                    result, in an undefined order. If False, only symbols
+                    actually defined and not merely referred to in the
+                    configuration will be included in the result, and will
+                    appear in the order that they are defined within the
+                    Kconfig configuration files."""
         return self.syms.values() if all_symbols else self.kconfig_syms
 
     def get_choices(self):
@@ -506,23 +521,26 @@ class Config():
         For example, if FOO and BAR are tristate symbols at least one of which
         has the value "y", then config.eval("y && (FOO || BAR)") => "y"
 
-        This functions always yields a tristate value. To get the value of
+        This function always yields a tristate value. To get the value of
         non-bool, non-tristate symbols, use Symbol.get_value().
 
         The result of this function is consistent with how evaluation works for
         conditional expressions in the configuration as well as in the C
         implementation. "m" and m are rewritten as '"m" && MODULES' and 'm &&
         MODULES', respectively, and a result of "m" will get promoted to "y" if
-        we're running without modules."""
+        we're running without modules.
+
+        Syntax checking is somewhat lax, partly to be compatible with lax
+        parsing in the C implementation."""
         return self._eval_expr(self._parse_expr(self._tokenize(s, True), # Feed
-                                                None, # Current symbol or choice
+                                                None, # Current symbol/choice
                                                 s))   # line
 
     def get_config_header(self):
         """Returns the (uncommented) textual header of the .config file most
         recently loaded with load_config(). Returns None if no .config file has
         been loaded or if the most recently loaded .config file has no header.
-        The header comprises all lines up to but not including the first line
+        The header consists of all lines up to but not including the first line
         that either
 
         1. Does not start with "#"
@@ -540,8 +558,7 @@ class Config():
         things like attempting to assign illegal values to symbols with
         Symbol.set_user_value()) should be printed to stderr.
 
-        print_warnings -- True if warnings should be
-                          printed, otherwise False."""
+        print_warnings -- True if warnings should be printed."""
         self.print_warnings = print_warnings
 
     def set_print_undef_assign(self, print_undef_assign):
@@ -572,42 +589,42 @@ class Config():
     def unset_user_values(self):
         """Resets the values of all symbols, as if Config.load_config() or
         Symbol.set_user_value() had never been called."""
-        for sym in self.syms.itervalues():
+        for sym in self.syms_iter():
             sym._unset_user_value_no_recursive_invalidate()
 
     def __str__(self):
         """Returns a string containing various information about the Config."""
-        return _sep_lines("Configuration",
-                          "File                                   : " + self.filename,
-                          "Base directory                         : " + self.base_dir,
-                          "Value of $ARCH at creation time        : " +
-                            ("(not set)" if self.arch is None else self.arch),
-                          "Value of $SRCARCH at creation time     : " +
-                            ("(not set)" if self.srcarch is None else self.srcarch),
-                          "Source tree (derived from $srctree;",
-                          "defaults to '.' if $srctree isn't set) : " + self.srctree,
-                          "Most recently loaded .config           : " +
-                            ("(no .config loaded)" if self.config_filename is None else
+        return _lines("Configuration",
+                      "File                                   : " +
+                        self.filename,
+                      "Base directory                         : " +
+                        self.base_dir,
+                      "Value of $ARCH at creation time        : " +
+                        ("(not set)" if self.arch is None else self.arch),
+                      "Value of $SRCARCH at creation time     : " +
+                        ("(not set)" if self.srcarch is None else
+                                        self.srcarch),
+                      "Source tree (derived from $srctree;",
+                      "defaults to '.' if $srctree isn't set) : " +
+                        self.srctree,
+                      "Most recently loaded .config           : " +
+                        ("(no .config loaded)"
+                          if self.config_filename is None else
                              self.config_filename),
-                          "Print warnings                         : " +
-                            bool_str[self.print_warnings],
-                          "Print assignments to undefined symbols : " +
-                            bool_str[self.print_undef_assign])
-
+                      "Print warnings                         : " +
+                        bool_str[self.print_warnings],
+                      "Print assignments to undefined symbols : " +
+                        bool_str[self.print_undef_assign])
 
     #
     # Private methods
     #
 
     def _invalidate_all(self):
-        for sym in self.syms.itervalues():
+        for sym in self.syms_iter():
             sym._invalidate()
 
-    def _tokenize(self,
-                  s,
-                  for_eval = False,
-                  filename = None,
-                  linenr = None):
+    def _tokenize(self, s, for_eval=False, filename=None, linenr=None):
         """Returns a _Feed instance containing tokens derived from the string
         's'. Registers any new symbols encountered (via _sym_lookup()).
 
@@ -617,7 +634,11 @@ class Config():
         for_eval -- True when parsing an expression for a call to
                     Config.eval(), in which case we should not treat the first
                     token specially nor register new symbols."""
-        s = s.lstrip()
+
+        # lstrip() would work here too, but removing the '\n' at the end leads
+        # to earlier termination in the 'while' loop below, saving lots of
+        # calls
+        s = s.strip()
         if s == "" or s[0] == "#":
             return _Feed([])
 
@@ -628,21 +649,21 @@ class Config():
         else:
             # The initial word on a line is parsed specially. Let
             # command_chars = [A-Za-z0-9_]. Then
-            #  - leading non-command_chars characters on the line are ignored, and
-            #  - the first token consists the following one or more command_chars
-            #    characters.
+            #  - leading non-command_chars characters are ignored, and
+            #  - the first token consists the following one or more
+            #    command_chars characters.
             # This is why things like "----help--" are accepted.
 
-            initial_token_match = initial_token_re.match(s)
+            initial_token_match = _initial_token_re_match(s)
             if initial_token_match is None:
                 return _Feed([])
             # The current index in the string being tokenized
             i = initial_token_match.end()
 
-            keyword = keywords.get(initial_token_match.group(1))
+            keyword = _get_keyword(initial_token_match.group(1))
             if keyword is None:
                 # We expect a keyword as the first token
-                _tokenization_error(s, len(s), filename, linenr)
+                _tokenization_error(s, filename, linenr)
             if keyword == T_HELP:
                 # Avoid junk after "help", e.g. "---", being registered as a
                 # symbol
@@ -659,7 +680,7 @@ class Config():
         while i < strlen:
             # Test for an identifier/keyword preceded by whitespace first; this
             # is the most common case.
-            id_keyword_match = id_keyword_re.match(s, i)
+            id_keyword_match = _id_keyword_re_match(s, i)
             if id_keyword_match:
                 # We have an identifier or keyword. The above also stripped any
                 # whitespace for us.
@@ -668,7 +689,7 @@ class Config():
                 i = id_keyword_match.end()
 
                 # Keyword?
-                keyword = keywords.get(name)
+                keyword = _get_keyword(name)
                 if keyword is not None:
                     append(keyword)
                 # What would ordinarily be considered a name is treated as a
@@ -700,97 +721,67 @@ class Config():
                 s = s[i:].lstrip()
                 if s == "":
                     break
-                strlen = len(s)
-                i = 0
                 c = s[0]
+                i = 1
 
                 # String literal (constant symbol)
                 if c == '"' or c == "'":
-                    i += 1
-
                     if "\\" in s:
                         # Slow path: This could probably be sped up, but it's a
                         # very unusual case anyway.
                         quote = c
-                        value = ""
+                        val = ""
                         while 1:
-                            if i >= strlen:
-                                _tokenization_error(s, strlen, filename,
-                                                    linenr)
+                            if i >= len(s):
+                                _tokenization_error(s, filename, linenr)
                             c = s[i]
                             if c == quote:
                                 break
                             if c == "\\":
-                                if i + 1 >= strlen:
-                                    _tokenization_error(s, strlen, filename,
-                                                        linenr)
-                                value += s[i + 1]
+                                if i + 1 >= len(s):
+                                    _tokenization_error(s, filename, linenr)
+                                val += s[i + 1]
                                 i += 2
                             else:
-                                value += c
+                                val += c
                                 i += 1
                         i += 1
-                        append(value)
+                        append(val)
                     else:
-                        # Fast path: If the string contains no backslashes (almost
-                        # always) we can simply look for the matching quote.
+                        # Fast path: If the string contains no backslashes
+                        # (almost always) we can simply look for the matching
+                        # quote.
                         end = s.find(c, i)
                         if end == -1:
-                            _tokenization_error(s, strlen, filename, linenr)
+                            _tokenization_error(s, filename, linenr)
                         append(s[i:end])
                         i = end + 1
 
                 elif c == "&":
-                    if i + 1 >= strlen:
-                        # Invalid characters are ignored
-                        continue
-                    if s[i + 1] != "&":
-                        # Invalid characters are ignored
-                        i += 1
-                        continue
+                    # Invalid characters are ignored
+                    if i >= len(s) or s[i] != "&": continue
                     append(T_AND)
-                    i += 2
+                    i += 1
 
                 elif c == "|":
-                    if i + 1 >= strlen:
-                        # Invalid characters are ignored
-                        continue
-                    if s[i + 1] != "|":
-                        # Invalid characters are ignored
-                        i += 1
-                        continue
+                    # Invalid characters are ignored
+                    if i >= len(s) or s[i] != "|": continue
                     append(T_OR)
-                    i += 2
+                    i += 1
 
                 elif c == "!":
-                    if i + 1 >= strlen:
-                        _tokenization_error(s, strlen, filename, linenr)
-                    if s[i + 1] == "=":
+                    if i < len(s) and s[i] == "=":
                         append(T_UNEQUAL)
-                        i += 2
+                        i += 1
                     else:
                         append(T_NOT)
-                        i += 1
-
-                elif c == "=":
-                    append(T_EQUAL)
-                    i += 1
 
-                elif c == "(":
-                    append(T_OPEN_PAREN)
-                    i += 1
-
-                elif c == ")":
-                    append(T_CLOSE_PAREN)
-                    i += 1
-
-                elif c == "#":
-                    break
+                elif c == "=": append(T_EQUAL)
+                elif c == "(": append(T_OPEN_PAREN)
+                elif c == ")": append(T_CLOSE_PAREN)
+                elif c == "#": break # Comment
 
-                else:
-                    # Invalid characters are ignored
-                    i += 1
-                    continue
+                else: continue # Invalid characters are ignored
 
             previous = tokens[-1]
 
@@ -810,22 +801,17 @@ class Config():
     #           <expr> '&&' <expr>
     #           <expr> '||' <expr>
 
-    def _parse_expr(self,
-                    feed,
-                    cur_sym_or_choice,
-                    line,
-                    filename = None,
-                    linenr = None,
-                    transform_m = True):
+    def _parse_expr(self, feed, cur_item, line, filename=None, linenr=None,
+                    transform_m=True):
         """Parse an expression from the tokens in 'feed' using a simple
         top-down approach. The result has the form (<operator>, <list
         containing parsed operands>).
 
         feed -- _Feed instance containing the tokens for the expression.
 
-        cur_sym_or_choice -- The symbol or choice currently being parsed, or
-                             None if we're not parsing a symbol or choice.
-                             Used for recording references to symbols.
+        cur_item -- The item (Symbol, Choice, Menu, or Comment) currently being
+                    parsed, or None if we're not parsing an item. Used for
+                    recording references to symbols.
 
         line -- The line containing the expression being parsed.
 
@@ -833,19 +819,18 @@ class Config():
 
         linenr (default: None) -- The line number containing the expression.
 
-        transform_m (default: False) -- Determines if 'm' should be rewritten to
-                                        'm && MODULES' -- see
-                                        parse_val_and_cond()."""
+        transform_m (default: False) -- Determines if 'm' should be rewritten
+                    to 'm && MODULES' -- see parse_val_and_cond()."""
 
         # Use instance variables to avoid having to pass these as arguments
         # through the top-down parser in _parse_expr_2(), which is tedious and
         # obfuscates the code. A profiler run shows no noticeable performance
         # difference.
-        self.parse_expr_cur_sym_or_choice = cur_sym_or_choice
-        self.parse_expr_line = line
-        self.parse_expr_filename = filename
-        self.parse_expr_linenr = linenr
-        self.parse_expr_transform_m = transform_m
+        self._cur_item = cur_item
+        self._transform_m = transform_m
+        self._line = line
+        self._filename = filename
+        self._linenr = linenr
 
         return self._parse_expr_2(feed)
 
@@ -854,7 +839,6 @@ class Config():
         # Keep parsing additional terms while the lookahead is '||'
         while feed.check(T_OR):
             or_terms.append(self._parse_or_term(feed))
-
         return or_terms[0] if len(or_terms) == 1 else (OR, or_terms)
 
     def _parse_or_term(self, feed):
@@ -862,129 +846,100 @@ class Config():
         # Keep parsing additional terms while the lookahead is '&&'
         while feed.check(T_AND):
             and_terms.append(self._parse_factor(feed))
-
         return and_terms[0] if len(and_terms) == 1 else (AND, and_terms)
 
     def _parse_factor(self, feed):
-        if feed.check(T_OPEN_PAREN):
-            expr_parse = self._parse_expr_2(feed)
+        token = feed.get_next()
+
+        if isinstance(token, (Symbol, str)):
+            if self._cur_item is not None and isinstance(token, Symbol):
+                self._cur_item.referenced_syms.add(token)
+
+            next_token = feed.peek_next()
+            # For conditional expressions ('depends on <expr>',
+            # '... if <expr>', # etc.), "m" and m are rewritten to
+            # "m" && MODULES.
+            if next_token != T_EQUAL and next_token != T_UNEQUAL:
+                if self._transform_m and (token is self.m or token == "m"):
+                    return (AND, ["m", self._sym_lookup("MODULES")])
+                return token
+
+            relation = EQUAL if (feed.get_next() == T_EQUAL) else UNEQUAL
+            token_2 = feed.get_next()
+            if self._cur_item is not None and isinstance(token_2, Symbol):
+                self._cur_item.referenced_syms.add(token_2)
+            return (relation, token, token_2)
+
+        if token == T_NOT:
+            return (NOT, self._parse_factor(feed))
 
+        if token == T_OPEN_PAREN:
+            expr_parse = self._parse_expr_2(feed)
             if not feed.check(T_CLOSE_PAREN):
-                _parse_error(self.parse_expr_line,
-                             "missing end parenthesis.",
-                             self.parse_expr_filename,
-                             self.parse_expr_linenr)
-
+                _parse_error(self._line, "missing end parenthesis",
+                             self._filename, self._linenr)
             return expr_parse
 
-        if feed.check(T_NOT):
-            return (NOT, self._parse_factor(feed))
-
-        sym_or_string = feed.get_next()
+        _parse_error(self._line, "malformed expression", self._filename,
+                     self._linenr)
 
-        if not isinstance(sym_or_string, (Symbol, str)):
-            _parse_error(self.parse_expr_line,
-                         "malformed expression.",
-                         self.parse_expr_filename,
-                         self.parse_expr_linenr)
-
-        if self.parse_expr_cur_sym_or_choice is not None and \
-           isinstance(sym_or_string, Symbol):
-            self.parse_expr_cur_sym_or_choice.referenced_syms.add(sym_or_string)
-
-        next_token = feed.peek_next()
-
-        # For conditional expressions ('depends on <expr>', '... if <expr>',
-        # etc.), "m" and m are rewritten to "m" && MODULES.
-        if next_token != T_EQUAL and next_token != T_UNEQUAL:
-            if self.parse_expr_transform_m and (sym_or_string is self.m or
-                                                sym_or_string == "m"):
-                return (AND, ["m", self._sym_lookup("MODULES")])
-            return sym_or_string
-
-        relation = EQUAL if (feed.get_next() == T_EQUAL) else UNEQUAL
-        sym_or_string_2 = feed.get_next()
-
-        if self.parse_expr_cur_sym_or_choice is not None and \
-           isinstance(sym_or_string_2, Symbol):
-            self.parse_expr_cur_sym_or_choice.referenced_syms.add(sym_or_string_2)
-
-        if sym_or_string is self.m:
-            sym_or_string = "m"
-
-        if sym_or_string_2 is self.m:
-            sym_or_string_2 = "m"
-
-        return (relation, sym_or_string, sym_or_string_2)
-
-    def _parse_file(self, filename, parent, deps, visible_if_deps, res = None):
-        """Parse the Kconfig file 'filename'. The result is a _Block with all
-        items from the file. See _parse_block() for the meaning of the
-        parameters."""
-        line_feeder = _FileFeed(_get_lines(filename), filename)
-        return self._parse_block(line_feeder, None, parent, deps, visible_if_deps, res)
+    def _parse_file(self, filename, parent, deps, visible_if_deps, res=None):
+        """Parses the Kconfig file 'filename'. Returns a list with the Items in
+        the file. See _parse_block() for the meaning of the parameters."""
+        return self._parse_block(_FileFeed(filename), None, parent, deps,
+                                 visible_if_deps, res)
 
     def _parse_block(self, line_feeder, end_marker, parent, deps,
-                     visible_if_deps = None, res = None):
+                     visible_if_deps=None, res=None):
         """Parses a block, which is the contents of either a file or an if,
-        menu, or choice statement. The result is a _Block with the items from
-        the block.
+        menu, or choice statement. Returns a list with the Items in the block.
 
         end_marker -- The token that ends the block, e.g. T_ENDIF ("endif") for
-                      if's. None for files.
+                      ifs. None for files.
 
         parent -- The enclosing menu, choice or if, or None if we're at the top
                   level.
 
-        deps -- Dependencies from enclosing menus, choices and if's.
+        deps -- Dependencies from enclosing menus, choices and ifs.
 
         visible_if_deps (default: None) -- 'visible if' dependencies from
                         enclosing menus.
 
-        res (default: None) -- The _Block to add items to. If None, a new
-                               _Block is created to hold the items."""
-
-        block = _Block() if res is None else res
+        res (default: None) -- The list to add items to. If None, a new list is
+            created to hold the items."""
 
-        filename = line_feeder.get_filename()
+        block = [] if res is None else res
 
         while 1:
-
             # Do we already have a tokenized line that we determined wasn't
             # part of whatever we were parsing earlier? See comment in
             # Config.__init__().
             if self.end_line is not None:
-                assert self.end_line_tokens is not None
+                line = self.end_line
                 tokens = self.end_line_tokens
                 tokens.go_to_start()
 
-                line = self.end_line
-                linenr = line_feeder.get_linenr()
-
                 self.end_line = None
                 self.end_line_tokens = None
-
             else:
                 line = line_feeder.get_next()
                 if line is None:
                     if end_marker is not None:
-                        raise Kconfig_Syntax_Error, (
+                        raise Kconfig_Syntax_Error(
                                 "Unexpected end of file {0}."
                                 .format(line_feeder.get_filename()))
                     return block
 
-                linenr = line_feeder.get_linenr()
-
-                tokens = self._tokenize(line, False, filename, linenr)
-
-            if tokens.is_empty():
-                continue
+                tokens = self._tokenize(line, False,
+                                        line_feeder.get_filename(),
+                                        line_feeder.get_linenr())
 
             t0 = tokens.get_next()
+            if t0 is None:
+                continue
 
-            # Have we reached the end of the block?
-            if t0 == end_marker:
-                return block
+            # Cases are ordered roughly by frequency, which speeds things up a
+            # bit
 
             if t0 == T_CONFIG or t0 == T_MENUCONFIG:
                 # The tokenizer will automatically allocate a new Symbol object
@@ -993,86 +948,117 @@ class Config():
                 sym = tokens.get_next()
 
                 # Symbols defined in multiple places get the parent of their
-                # first definition. However, for symbols whose parents are choice
-                # statements, the choice statement takes precedence.
+                # first definition. However, for symbols whose parents are
+                # choice statements, the choice statement takes precedence.
                 if not sym.is_defined_ or isinstance(parent, Choice):
                     sym.parent = parent
 
                 sym.is_defined_ = True
 
                 self.kconfig_syms.append(sym)
-                block.add_item(sym)
+                block.append(sym)
 
                 self._parse_properties(line_feeder, sym, deps, visible_if_deps)
 
+            elif t0 == T_SOURCE:
+                kconfig_file = tokens.get_next()
+                exp_kconfig_file = self._expand_sym_refs(kconfig_file)
+                f = os.path.join(self.base_dir, exp_kconfig_file)
+                if not os.path.exists(f):
+                    raise IOError('{0}:{1}: sourced file "{2}" (expands to '
+                                  '"{3}") not found. Perhaps base_dir '
+                                  '(argument to Config.__init__(), currently '
+                                  '"{4}") is set to the wrong value.'
+                                  .format(line_feeder.get_filename(),
+                                          line_feeder.get_linenr(),
+                                          kconfig_file, exp_kconfig_file,
+                                          self.base_dir))
+
+                # Add items to the same block
+                self._parse_file(f, parent, deps, visible_if_deps, block)
+
+            elif t0 == end_marker:
+                # We have reached the end of the block
+                return block
+
+            elif t0 == T_IF:
+                # If statements are treated as syntactic sugar for adding
+                # dependencies to enclosed items and do not have an explicit
+                # object representation.
+
+                dep_expr = self._parse_expr(tokens, None, line,
+                                            line_feeder.get_filename(),
+                                            line_feeder.get_linenr())
+                # Add items to the same block
+                self._parse_block(line_feeder, T_ENDIF, parent,
+                                  _make_and(dep_expr, deps),
+                                  visible_if_deps, block)
+
+            elif t0 == T_COMMENT:
+                comment = Comment()
+
+                comment.config = self
+                comment.parent = parent
+                comment.filename = line_feeder.get_filename()
+                comment.linenr = line_feeder.get_linenr()
+                comment.text = tokens.get_next()
+
+                self.comments.append(comment)
+                block.append(comment)
+
+                self._parse_properties(line_feeder, comment, deps,
+                                       visible_if_deps)
+
             elif t0 == T_MENU:
                 menu = Menu()
-                self.menus.append(menu)
+
                 menu.config = self
                 menu.parent = parent
+                menu.filename = line_feeder.get_filename()
+                menu.linenr = line_feeder.get_linenr()
                 menu.title = tokens.get_next()
 
-                menu.filename = filename
-                menu.linenr = linenr
+                self.menus.append(menu)
+                block.append(menu)
 
                 # Parse properties and contents
-                self._parse_properties(line_feeder, menu, deps, visible_if_deps)
-                menu.block = self._parse_block(line_feeder,
-                                               T_ENDMENU,
-                                               menu,
+                self._parse_properties(line_feeder, menu, deps,
+                                       visible_if_deps)
+                menu.block = self._parse_block(line_feeder, T_ENDMENU, menu,
                                                menu.dep_expr,
                                                _make_and(visible_if_deps,
                                                          menu.visible_if_expr))
 
-                block.add_item(menu)
-
-            elif t0 == T_IF:
-                # If statements are treated as syntactic sugar for adding
-                # dependencies to enclosed items and do not have an explicit
-                # object representation.
-
-                dep_expr = self._parse_expr(tokens, None, line, filename, linenr)
-                self._parse_block(line_feeder,
-                                  T_ENDIF,
-                                  parent,
-                                  _make_and(dep_expr, deps),
-                                  visible_if_deps,
-                                  block) # Add items to the same block
-
             elif t0 == T_CHOICE:
-                # We support named choices
-                already_defined = False
-                name = None
-                if len(tokens) > 1 and isinstance(tokens[1], str):
-                    name = tokens[1]
-                    already_defined = name in self.named_choices
-
-                if already_defined:
-                    choice = self.named_choices[name]
-                else:
+                name = tokens.get_next()
+                if name is None:
                     choice = Choice()
                     self.choices.append(choice)
-                    if name is not None:
+                else:
+                    # Named choice
+                    choice = self.named_choices.get(name)
+                    if choice is None:
+                        choice = Choice()
                         choice.name = name
                         self.named_choices[name] = choice
+                        self.choices.append(choice)
 
                 choice.config = self
                 choice.parent = parent
 
-                choice.def_locations.append((filename, linenr))
+                choice.def_locations.append((line_feeder.get_filename(),
+                                             line_feeder.get_linenr()))
 
                 # Parse properties and contents
-                self._parse_properties(line_feeder, choice, deps, visible_if_deps)
-                choice.block = self._parse_block(line_feeder,
-                                                 T_ENDCHOICE,
-                                                 choice,
-                                                 None,
-                                                 visible_if_deps)
+                self._parse_properties(line_feeder, choice, deps,
+                                       visible_if_deps)
+                choice.block = self._parse_block(line_feeder, T_ENDCHOICE,
+                                                 choice, deps, visible_if_deps)
 
                 choice._determine_actual_symbols()
 
-                # If no type is set for the choice, its type is that of the first
-                # choice item
+                # If no type is set for the choice, its type is that of the
+                # first choice item
                 if choice.type == UNKNOWN:
                     for item in choice.get_symbols():
                         if item.type != UNKNOWN:
@@ -1084,71 +1070,35 @@ class Config():
                     if item.type == UNKNOWN:
                         item.type = choice.type
 
-                # For named choices defined in multiple locations, only record
-                # at the first definition
-                if not already_defined:
-                    block.add_item(choice)
-
-            elif t0 == T_COMMENT:
-                comment = Comment()
-                comment.config = self
-                comment.parent = parent
-
-                comment.filename = filename
-                comment.linenr = linenr
-
-                comment.text = tokens.get_next()
-                self._parse_properties(line_feeder, comment, deps, visible_if_deps)
-
-                block.add_item(comment)
-                self.comments.append(comment)
-
-            elif t0 == T_SOURCE:
-                kconfig_file = tokens.get_next()
-                exp_kconfig_file = self._expand_sym_refs(kconfig_file)
-                f = os.path.join(self.base_dir, exp_kconfig_file)
-
-                if not os.path.exists(f):
-                    raise IOError, ('{0}:{1}: sourced file "{2}" (expands to\n'
-                                    '"{3}") not found. Perhaps base_dir\n'
-                                    '(argument to Config.__init__(), currently\n'
-                                    '"{4}") is set to the wrong value.'
-                                    .format(filename,
-                                            linenr,
-                                            kconfig_file,
-                                            exp_kconfig_file,
-                                            self.base_dir))
-
-                # Add items to the same block
-                self._parse_file(f, parent, deps, visible_if_deps, block)
+                block.append(choice)
 
             elif t0 == T_MAINMENU:
                 text = tokens.get_next()
-
                 if self.mainmenu_text is not None:
                     self._warn("overriding 'mainmenu' text. "
                                'Old value: "{0}", new value: "{1}".'
-                                .format(self.mainmenu_text, text),
-                               filename,
-                               linenr)
-
+                               .format(self.mainmenu_text, text),
+                               line_feeder.get_filename(),
+                               line_feeder.get_linenr())
                 self.mainmenu_text = text
 
             else:
-                _parse_error(line, "unrecognized construct.", filename, linenr)
+                _parse_error(line, "unrecognized construct",
+                             line_feeder.get_filename(),
+                             line_feeder.get_linenr())
 
     def _parse_properties(self, line_feeder, stmt, deps, visible_if_deps):
-        """Parsing of properties for symbols, menus, choices, and comments."""
+        """Parsing of properties for symbols, menus, choices, and comments.
+        Takes care of propagating dependencies from enclosing menus and ifs."""
 
         def parse_val_and_cond(tokens, line, filename, linenr):
             """Parses '<expr1> if <expr2>' constructs, where the 'if' part is
             optional. Returns a tuple containing the parsed expressions, with
             None as the second element if the 'if' part is missing."""
             val = self._parse_expr(tokens, stmt, line, filename, linenr, False)
-
             if tokens.check(T_IF):
-                return (val, self._parse_expr(tokens, stmt, line, filename, linenr))
-
+                return (val, self._parse_expr(tokens, stmt, line, filename,
+                                              linenr))
             return (val, None)
 
         # In case the symbol is defined in multiple locations, we need to
@@ -1172,41 +1122,53 @@ class Config():
 
             tokens = self._tokenize(line, False, filename, linenr)
 
-            if tokens.is_empty():
+            t0 = tokens.get_next()
+            if t0 is None:
                 continue
 
-            t0 = tokens.get_next()
+            # Cases are ordered roughly by frequency, which speeds things up a
+            # bit
 
-            if t0 == T_HELP:
-                # Find first non-empty line and get its indentation
+            if t0 == T_DEPENDS:
+                if not tokens.check(T_ON):
+                    _parse_error(line, 'expected "on" after "depends"',
+                                 filename, linenr)
 
-                line_feeder.remove_while(str.isspace)
-                line = line_feeder.get_next()
+                parsed_deps = self._parse_expr(tokens, stmt, line, filename,
+                                               linenr)
+
+                if isinstance(stmt, (Menu, Comment)):
+                    stmt.orig_deps = _make_and(stmt.orig_deps, parsed_deps)
+                else:
+                    depends_on_expr = _make_and(depends_on_expr, parsed_deps)
 
+            elif t0 == T_HELP:
+                # Find first non-blank (not all-space) line and get its
+                # indentation
+
+                line_feeder.remove_blank()
+                line = line_feeder.get_next()
                 if line is None:
                     stmt.help = ""
                     break
 
                 indent = _indentation(line)
-
-                # If the first non-empty lines has zero indent, there is no
-                # help text
                 if indent == 0:
+                    # If the first non-empty lines has zero indent, there is no
+                    # help text
                     stmt.help = ""
                     line_feeder.go_back()
                     break
 
-                help_lines = [_deindent(line, indent)]
-
                 # The help text goes on till the first non-empty line with less
                 # indent
+                help_lines = [_deindent(line, indent)]
                 while 1:
                     line = line_feeder.get_next()
-                    if (line is None) or \
+                    if line is None or \
                        (not line.isspace() and _indentation(line) < indent):
                         stmt.help = "".join(help_lines)
                         break
-
                     help_lines.append(_deindent(line, indent))
 
                 if line is None:
@@ -1214,39 +1176,6 @@ class Config():
 
                 line_feeder.go_back()
 
-            elif t0 == T_PROMPT:
-                # 'prompt' properties override each other within a single
-                # definition of a symbol, but additional prompts can be added
-                # by defining the symbol multiple times; hence 'new_prompt'
-                # instead of 'prompt'.
-                new_prompt = parse_val_and_cond(tokens, line, filename, linenr)
-
-            elif t0 == T_DEFAULT:
-                new_def_exprs.append(parse_val_and_cond(tokens, line, filename, linenr))
-
-            elif t0 == T_DEPENDS:
-                if not tokens.check(T_ON):
-                    _parse_error(line, 'expected "on" after "depends".', filename, linenr)
-
-                parsed_deps = self._parse_expr(tokens, stmt, line, filename, linenr)
-
-                if isinstance(stmt, (Menu, Comment)):
-                    stmt.dep_expr = _make_and(stmt.dep_expr, parsed_deps)
-                else:
-                    depends_on_expr = _make_and(depends_on_expr, parsed_deps)
-
-            elif t0 == T_VISIBLE:
-                if not tokens.check(T_IF):
-                    _parse_error(line, 'expected "if" after "visible".', filename, linenr)
-                if not isinstance(stmt, Menu):
-                    _parse_error(line,
-                                 "'visible if' is only valid for menus.",
-                                 filename,
-                                 linenr)
-
-                parsed_deps = self._parse_expr(tokens, stmt, line, filename, linenr)
-                stmt.visible_if_expr = _make_and(stmt.visible_if_expr, parsed_deps)
-
             elif t0 == T_SELECT:
                 target = tokens.get_next()
 
@@ -1255,15 +1184,33 @@ class Config():
 
                 if tokens.check(T_IF):
                     new_selects.append((target,
-                                        self._parse_expr(tokens, stmt, line, filename, linenr)))
+                                        self._parse_expr(tokens, stmt, line,
+                                                         filename, linenr)))
                 else:
                     new_selects.append((target, None))
 
             elif t0 in (T_BOOL, T_TRISTATE, T_INT, T_HEX, T_STRING):
                 stmt.type = token_to_type[t0]
+                if len(tokens) > 1:
+                    new_prompt = parse_val_and_cond(tokens, line, filename,
+                                                    linenr)
+
+            elif t0 == T_DEFAULT:
+                new_def_exprs.append(parse_val_and_cond(tokens, line, filename,
+                                                        linenr))
 
+            elif t0 == T_DEF_BOOL:
+                stmt.type = BOOL
                 if len(tokens) > 1:
-                    new_prompt = parse_val_and_cond(tokens, line, filename, linenr)
+                    new_def_exprs.append(parse_val_and_cond(tokens, line,
+                                                            filename, linenr))
+
+            elif t0 == T_PROMPT:
+                # 'prompt' properties override each other within a single
+                # definition of a symbol, but additional prompts can be added
+                # by defining the symbol multiple times; hence 'new_prompt'
+                # instead of 'prompt'.
+                new_prompt = parse_val_and_cond(tokens, line, filename, linenr)
 
             elif t0 == T_RANGE:
                 lower = tokens.get_next()
@@ -1273,29 +1220,16 @@ class Config():
 
                 if tokens.check(T_IF):
                     stmt.ranges.append((lower, upper,
-                                        self._parse_expr(tokens, stmt, line, filename, linenr)))
+                                        self._parse_expr(tokens, stmt, line,
+                                                         filename, linenr)))
                 else:
                     stmt.ranges.append((lower, upper, None))
 
-            elif t0 == T_DEF_BOOL:
-                stmt.type = BOOL
-
-                if len(tokens) > 1:
-                    new_def_exprs.append(parse_val_and_cond(tokens, line, filename, linenr))
-
             elif t0 == T_DEF_TRISTATE:
                 stmt.type = TRISTATE
-
                 if len(tokens) > 1:
-                    new_def_exprs.append(parse_val_and_cond(tokens, line, filename, linenr))
-
-            elif t0 == T_OPTIONAL:
-                if not isinstance(stmt, Choice):
-                    _parse_error(line,
-                                 '"optional" is only valid for choices.',
-                                 filename,
-                                 linenr)
-                stmt.optional = True
+                    new_def_exprs.append(parse_val_and_cond(tokens, line,
+                                                            filename, linenr))
 
             elif t0 == T_OPTION:
                 if tokens.check(T_ENV) and tokens.check(T_EQUAL):
@@ -1305,117 +1239,145 @@ class Config():
                     stmt.is_from_env = True
 
                     if env_var not in os.environ:
-                        self._warn("""
-The symbol {0} references the non-existent environment variable {1} and will
-get the empty string as its value.
-
-If you're using kconfiglib via 'make (i)scriptconfig' it should have set up the
-environment correctly for you. If you still got this message, that might be an
-error, and you should e-mail kconfiglib at gmail.com.
-."""                               .format(stmt.name, env_var),
-                                   filename,
-                                   linenr)
-
-                        stmt.cached_value = ""
+                        self._warn("The symbol {0} references the "
+                                   "non-existent environment variable {1} and "
+                                   "will get the empty string as its value. "
+                                   "If you're using kconfiglib via "
+                                   "'make (i)scriptconfig', it should have "
+                                   "set up the environment correctly for you. "
+                                   "If you still got this message, that "
+                                   "might be an error, and you should email "
+                                   "ulfalizer a.t Google's email service."""
+                                   .format(stmt.name, env_var),
+                                   filename, linenr)
+
+                        stmt.cached_val = ""
                     else:
-                        stmt.cached_value = os.environ[env_var]
+                        stmt.cached_val = os.environ[env_var]
 
                 elif tokens.check(T_DEFCONFIG_LIST):
                     self.defconfig_sym = stmt
 
                 elif tokens.check(T_MODULES):
-                    self._warn("the 'modules' option is not supported. "
-                               "Let me know if this is a problem for you; "
-                               "it shouldn't be that hard to implement.",
-                               filename,
-                               linenr)
+                    # To reduce warning spam, only warn if 'option modules' is
+                    # set on some symbol that isn't MODULES, which should be
+                    # safe. I haven't run into any projects that make use
+                    # modules besides the kernel yet, and there it's likely to
+                    # keep being called "MODULES".
+                    if stmt.name != "MODULES":
+                        self._warn("the 'modules' option is not supported. "
+                                   "Let me know if this is a problem for you; "
+                                   "it shouldn't be that hard to implement. "
+                                   "(Note that modules are still supported -- "
+                                   "Kconfiglib just assumes the symbol name "
+                                   "MODULES, like older versions of the C "
+                                   "implementation did when 'option modules' "
+                                   "wasn't used.)",
+                                   filename, linenr)
+
+                elif tokens.check(T_ALLNOCONFIG_Y):
+                    if not isinstance(stmt, Symbol):
+                        _parse_error(line,
+                                     "the 'allnoconfig_y' option is only "
+                                     "valid for symbols",
+                                     filename,
+                                     linenr)
+                    stmt.allnoconfig_y = True
 
                 else:
-                    _parse_error(line, "unrecognized option.", filename, linenr)
+                    _parse_error(line, "unrecognized option", filename, linenr)
 
-            else:
-                # See comment in Config.__init__()
-                self.end_line = line
-                self.end_line_tokens = tokens
-                break
+            elif t0 == T_VISIBLE:
+                if not tokens.check(T_IF):
+                    _parse_error(line, 'expected "if" after "visible"',
+                                 filename, linenr)
+                if not isinstance(stmt, Menu):
+                    _parse_error(line,
+                                 "'visible if' is only valid for menus",
+                                 filename, linenr)
 
-        # Propagate dependencies from enclosing menus and if's.
+                parsed_deps = self._parse_expr(tokens, stmt, line, filename,
+                                               linenr)
+                stmt.visible_if_expr = _make_and(stmt.visible_if_expr,
+                                                 parsed_deps)
 
-        # For menus and comments..
-        if isinstance(stmt, (Menu, Comment)):
-            stmt.orig_deps = stmt.dep_expr
-            stmt.deps_from_containing = deps
-            stmt.dep_expr = _make_and(stmt.dep_expr, deps)
+            elif t0 == T_OPTIONAL:
+                if not isinstance(stmt, Choice):
+                    _parse_error(line,
+                                 '"optional" is only valid for choices',
+                                 filename,
+                                 linenr)
+                stmt.optional = True
+
+            else:
+                # See comment in Config.__init__()
+                self.end_line = line
+                self.end_line_tokens = tokens
+                break
+
+        # Done parsing properties. Now propagate 'depends on' and enclosing
+        # menu/if dependencies to expressions.
 
-            stmt.all_referenced_syms = \
-              stmt.referenced_syms | _get_expr_syms(deps)
+        # The set of symbols referenced directly by the statement plus all
+        # symbols referenced by enclosing menus and ifs
+        stmt.all_referenced_syms = stmt.referenced_syms | _get_expr_syms(deps)
 
-        # For symbols and choices..
+        # Save original dependencies from enclosing menus and ifs
+        stmt.deps_from_containing = deps
+
+        if isinstance(stmt, (Menu, Comment)):
+            stmt.dep_expr = _make_and(stmt.orig_deps, deps)
         else:
+            # Symbol or Choice
 
             # See comment for 'menu_dep'
             stmt.menu_dep = depends_on_expr
 
-            # Propagate dependencies specified with 'depends on' to any new
-            # default expressions, prompts, and selections. ("New" since a
-            # symbol might be defined in multiple places and the dependencies
-            # should only apply to the local definition.)
-
-            new_def_exprs = [(val_expr, _make_and(cond_expr, depends_on_expr))
-                             for (val_expr, cond_expr) in new_def_exprs]
-
-            new_selects = [(target, _make_and(cond_expr, depends_on_expr))
-                           for (target, cond_expr) in new_selects]
+            # Propagate dependencies to prompts
 
             if new_prompt is not None:
+                # Propagate 'visible if' dependencies from enclosing menus
                 prompt, cond_expr = new_prompt
-
-                # 'visible if' dependencies from enclosing menus get propagated
-                # to prompts
-                if visible_if_deps is not None:
-                    cond_expr = _make_and(cond_expr, visible_if_deps)
-
+                cond_expr = _make_and(cond_expr, visible_if_deps)
+                # Propagate 'depends on' dependencies
                 new_prompt = (prompt, _make_and(cond_expr, depends_on_expr))
+                # Save original
+                stmt.orig_prompts.append(new_prompt)
+                # Finalize with dependencies from enclosing menus and ifs
+                stmt.prompts.append((new_prompt[0],
+                                    _make_and(new_prompt[1], deps)))
 
-            # We save the original expressions -- before any menu and if
-            # conditions have been propagated -- so these can be retrieved
-            # later.
+            # Propagate dependencies to defaults
 
+            # Propagate 'depends on' dependencies
+            new_def_exprs = [(val_expr, _make_and(cond_expr, depends_on_expr))
+                             for val_expr, cond_expr in new_def_exprs]
+            # Save original
             stmt.orig_def_exprs.extend(new_def_exprs)
-            if new_prompt is not None:
-                stmt.orig_prompts.append(new_prompt)
+            # Finalize with dependencies from enclosing menus and ifs
+            stmt.def_exprs.extend([(val_expr, _make_and(cond_expr, deps))
+                                   for val_expr, cond_expr in new_def_exprs])
+
+            # Propagate dependencies to selects
 
             # Only symbols can select
             if isinstance(stmt, Symbol):
+                # Propagate 'depends on' dependencies
+                new_selects = [(target, _make_and(cond_expr, depends_on_expr))
+                               for target, cond_expr in new_selects]
+                # Save original
                 stmt.orig_selects.extend(new_selects)
-
-            # Save dependencies from enclosing menus and if's
-            stmt.deps_from_containing = deps
-
-            # The set of symbols referenced directly by the symbol/choice plus
-            # all symbols referenced by enclosing menus and if's.
-            stmt.all_referenced_syms = \
-              stmt.referenced_syms | _get_expr_syms(deps)
-
-            # Propagate dependencies from enclosing menus and if's
-
-            stmt.def_exprs.extend([(val_expr, _make_and(cond_expr, deps))
-                                   for (val_expr, cond_expr) in new_def_exprs])
-
-            for (target, cond) in new_selects:
-                target.rev_dep = _make_or(target.rev_dep,
-                                          _make_and(stmt,
-                                                    _make_and(cond, deps)))
-
-            if new_prompt is not None:
-                prompt, cond_expr = new_prompt
-                stmt.prompts.append((prompt, _make_and(cond_expr, deps)))
+                # Finalize with dependencies from enclosing menus and ifs
+                for target, cond in new_selects:
+                    target.rev_dep = _make_or(target.rev_dep,
+                                              _make_and(stmt,
+                                                        _make_and(cond, deps)))
 
     #
     # Symbol table manipulation
     #
 
-    def _sym_lookup(self, name, add_sym_if_not_exists = True):
+    def _sym_lookup(self, name, add_sym_if_not_exists=True):
         """Fetches the symbol 'name' from the symbol table, optionally adding
         it if it does not exist (this is usually what we want)."""
         if name in self.syms:
@@ -1468,75 +1430,59 @@ error, and you should e-mail kconfiglib at gmail.com.
 
         first_expr = expr[0]
 
-        if first_expr == OR:
-            res = "n"
-
-            for subexpr in expr[1]:
-                ev = self._eval_expr_2(subexpr)
-
-                # Return immediately upon discovering a "y" term
-                if ev == "y":
-                    return "y"
-
-                if ev == "m":
-                    res = "m"
-
-            # 'res' is either "n" or "m" here; we already handled the
-            # short-circuiting "y" case in the loop.
-            return res
-
         if first_expr == AND:
             res = "y"
-
             for subexpr in expr[1]:
                 ev = self._eval_expr_2(subexpr)
-
                 # Return immediately upon discovering an "n" term
                 if ev == "n":
                     return "n"
-
                 if ev == "m":
                     res = "m"
-
             # 'res' is either "m" or "y" here; we already handled the
             # short-circuiting "n" case in the loop.
             return res
 
+        if first_expr == OR:
+            res = "n"
+            for subexpr in expr[1]:
+                ev = self._eval_expr_2(subexpr)
+                # Return immediately upon discovering a "y" term
+                if ev == "y":
+                    return "y"
+                if ev == "m":
+                    res = "m"
+            # 'res' is either "n" or "m" here; we already handled the
+            # short-circuiting "y" case in the loop.
+            return res
+
         if first_expr == NOT:
             ev = self._eval_expr_2(expr[1])
-
             if ev == "y":
                 return "n"
-
             return "y" if (ev == "n") else "m"
 
         if first_expr == EQUAL:
-            return "y" if (self._get_str_value(expr[1]) ==
-                           self._get_str_value(expr[2])) else "n"
+            return "y" if (_str_val(expr[1]) == _str_val(expr[2])) else "n"
 
         if first_expr == UNEQUAL:
-            return "y" if (self._get_str_value(expr[1]) !=
-                           self._get_str_value(expr[2])) else "n"
+            return "y" if (_str_val(expr[1]) != _str_val(expr[2])) else "n"
 
         _internal_error("Internal error while evaluating expression: "
                         "unknown operation {0}.".format(first_expr))
 
-    def _get_str_value(self, obj):
-        if isinstance(obj, str):
-            return obj
-        # obj is a Symbol
-        return obj.get_value()
-
     def _eval_min(self, e1, e2):
+        """Returns the minimum value of the two expressions. Equates None with
+        'y'."""
         e1_eval = self._eval_expr(e1)
         e2_eval = self._eval_expr(e2)
-
         return e1_eval if tri_less(e1_eval, e2_eval) else e2_eval
 
     def _eval_max(self, e1, e2):
+        """Returns the maximum value of the two expressions. Equates None with
+        'y'."""
         e1_eval = self._eval_expr(e1)
         e2_eval = self._eval_expr(e2)
-
         return e1_eval if tri_greater(e1_eval, e2_eval) else e2_eval
 
     #
@@ -1558,8 +1504,6 @@ error, and you should e-mail kconfiglib at gmail.com.
         for caching/invalidation purposes. The calculated sets might be larger
         than necessary as we don't do any complicated analysis of the
         expressions."""
-        for sym in self.syms.itervalues():
-            sym.dep = set()
 
         # Adds 'sym' as a directly dependent symbol to all symbols that appear
         # in the expression 'e'
@@ -1574,31 +1518,30 @@ error, and you should e-mail kconfiglib at gmail.com.
         #    (these won't be included in 'dep' as that makes the dependency
         #    graph unwieldy, but Symbol._get_dependent() will include them)
         #  - Any symbols in a choice statement that depends on the symbol
-        for sym in self.syms.itervalues():
-            for (_, e) in sym.prompts:
+        for sym in self.syms_iter():
+            for _, e in sym.prompts:
                 add_expr_deps(e, sym)
 
-            for (v, e) in sym.def_exprs:
+            for v, e in sym.def_exprs:
                 add_expr_deps(v, sym)
                 add_expr_deps(e, sym)
 
             add_expr_deps(sym.rev_dep, sym)
 
-            for (l, u, e) in sym.ranges:
+            for l, u, e in sym.ranges:
                 add_expr_deps(l, sym)
                 add_expr_deps(u, sym)
                 add_expr_deps(e, sym)
 
             if sym.is_choice_symbol_:
                 choice = sym.parent
-
-                for (_, e) in choice.prompts:
+                for _, e in choice.prompts:
                     add_expr_deps(e, sym)
-
-                for (_, e) in choice.def_exprs:
+                for _, e in choice.def_exprs:
                     add_expr_deps(e, sym)
 
-    def _expr_val_str(self, expr, no_value_str = "(none)", get_val_instead_of_eval = False):
+    def _expr_val_str(self, expr, no_value_str="(none)",
+                      get_val_instead_of_eval=False):
         # Since values are valid expressions, _expr_to_str() will get a nice
         # string representation for those as well.
 
@@ -1619,17 +1562,17 @@ error, and you should e-mail kconfiglib at gmail.com.
         empty string for undefined symbols."""
 
         while 1:
-            sym_ref_re_match = sym_ref_re.search(s)
-            if sym_ref_re_match is None:
+            sym_ref_match = _sym_ref_re_search(s)
+            if sym_ref_match is None:
                 return s
 
-            sym_name = sym_ref_re_match.group(0)[1:]
+            sym_name = sym_ref_match.group(0)[1:]
             sym = self.syms.get(sym_name)
             expansion = "" if sym is None else sym.get_value()
 
-            s = s[:sym_ref_re_match.start()] + \
+            s = s[:sym_ref_match.start()] + \
                 expansion + \
-                s[sym_ref_re_match.end():]
+                s[sym_ref_match.end():]
 
     def _get_sym_or_choice_str(self, sc):
         """Symbols and choices have many properties in common, so we factor out
@@ -1643,120 +1586,108 @@ error, and you should e-mail kconfiglib at gmail.com.
         # Common symbol/choice properties
         #
 
-        user_value_str = "(no user value)" if sc.user_val is None else s(sc.user_val)
-
-        visibility_str = s(sc.get_visibility())
+        user_val_str = "(no user value)" if sc.user_val is None else \
+                       s(sc.user_val)
 
         # Build prompts string
-        if sc.prompts == []:
+        if not sc.prompts:
             prompts_str = " (no prompts)"
         else:
             prompts_str_rows = []
-
-            for (prompt, cond_expr) in sc.orig_prompts:
+            for prompt, cond_expr in sc.orig_prompts:
                 if cond_expr is None:
                     prompts_str_rows.append(' "{0}"'.format(prompt))
                 else:
-                    prompts_str_rows.append(' "{0}" if '.format(prompt) +
-                                            self._expr_val_str(cond_expr))
-
+                    prompts_str_rows.append(
+                      ' "{0}" if {1}'.format(prompt,
+                                             self._expr_val_str(cond_expr)))
             prompts_str = "\n".join(prompts_str_rows)
 
         # Build locations string
-        if sc.def_locations == []:
+        if not sc.def_locations:
             locations_str = "(no locations)"
         else:
             locations_str = " ".join(["{0}:{1}".format(filename, linenr) for
                                       (filename, linenr) in sc.def_locations])
 
-        # Build additional-dependencies-from-menus-and-if's string
-        additional_deps_str = " " + self._expr_val_str(sc.deps_from_containing,
-                                                       "(no additional dependencies)")
+        # Build additional-dependencies-from-menus-and-ifs string
+        additional_deps_str = " " + \
+          self._expr_val_str(sc.deps_from_containing,
+                             "(no additional dependencies)")
 
         #
         # Symbol-specific stuff
         #
 
         if isinstance(sc, Symbol):
-
-            # Build value string
-            value_str = s(sc.get_value())
-
             # Build ranges string
             if isinstance(sc, Symbol):
-                if sc.ranges == []:
+                if not sc.ranges:
                     ranges_str = " (no ranges)"
                 else:
                     ranges_str_rows = []
-
-                    for (l, u, cond_expr) in sc.ranges:
+                    for l, u, cond_expr in sc.ranges:
                         if cond_expr is None:
-                            ranges_str_rows.append(" [{0}, {1}]".format(s(l), s(u)))
+                            ranges_str_rows.append(" [{0}, {1}]".format(s(l),
+                                                                        s(u)))
                         else:
                             ranges_str_rows.append(" [{0}, {1}] if {2}"
-                                                   .format(s(l), s(u), self._expr_val_str(cond_expr)))
-
+                              .format(s(l), s(u),
+                                      self._expr_val_str(cond_expr)))
                     ranges_str = "\n".join(ranges_str_rows)
 
             # Build default values string
-            if sc.def_exprs == []:
+            if not sc.def_exprs:
                 defaults_str = " (no default values)"
             else:
                 defaults_str_rows = []
-
-                for (val_expr, cond_expr) in sc.orig_def_exprs:
-                    row_str = " " + self._expr_val_str(val_expr, "(none)", sc.type == STRING)
+                for val_expr, cond_expr in sc.orig_def_exprs:
+                    row_str = " " + self._expr_val_str(val_expr, "(none)",
+                                                       sc.type == STRING)
                     defaults_str_rows.append(row_str)
-                    defaults_str_rows.append("  Condition: " + self._expr_val_str(cond_expr))
-
+                    defaults_str_rows.append("  Condition: " +
+                                               self._expr_val_str(cond_expr))
                 defaults_str = "\n".join(defaults_str_rows)
 
             # Build selects string
-            if sc.orig_selects == []:
+            if not sc.orig_selects:
                 selects_str = " (no selects)"
             else:
                 selects_str_rows = []
-
-                for (target, cond_expr) in sc.orig_selects:
+                for target, cond_expr in sc.orig_selects:
                     if cond_expr is None:
                         selects_str_rows.append(" {0}".format(target.name))
                     else:
-                        selects_str_rows.append(" {0} if ".format(target.name) +
-                                                self._expr_val_str(cond_expr))
-
+                        selects_str_rows.append(
+                          " {0} if {1}".format(target.name,
+                                               self._expr_val_str(cond_expr)))
                 selects_str = "\n".join(selects_str_rows)
 
-            # Build reverse dependencies string
-            if sc.rev_dep == "n":
-                rev_dep_str = " (no reverse dependencies)"
-            else:
-                rev_dep_str = " " + self._expr_val_str(sc.rev_dep)
-
-            res = _sep_lines("Symbol " + (sc.name if sc.name is not None else "(no name)"),
-                             "Type           : " + typename[sc.type],
-                             "Value          : " + value_str,
-                             "User value     : " + user_value_str,
-                             "Visibility     : " + visibility_str,
-                             "Is choice item : " + bool_str[sc.is_choice_symbol_],
-                             "Is defined     : " + bool_str[sc.is_defined_],
-                             "Is from env.   : " + bool_str[sc.is_from_env],
-                             "Is special     : " + bool_str[sc.is_special_] + "\n")
-
-            if sc.ranges != []:
-                res += _sep_lines("Ranges:",
-                                  ranges_str + "\n")
-
-            res += _sep_lines("Prompts:",
-                              prompts_str,
-                              "Default values:",
-                              defaults_str,
-                              "Selects:",
-                              selects_str,
-                              "Reverse dependencies:",
-                              rev_dep_str,
-                              "Additional dependencies from enclosing menus and if's:",
-                              additional_deps_str,
-                              "Locations: " + locations_str)
+            res = _lines("Symbol " +
+                           ("(no name)" if sc.name is None else sc.name),
+                         "Type           : " + typename[sc.type],
+                         "Value          : " + s(sc.get_value()),
+                         "User value     : " + user_val_str,
+                         "Visibility     : " + s(sc.get_visibility()),
+                         "Is choice item : " + bool_str[sc.is_choice_symbol_],
+                         "Is defined     : " + bool_str[sc.is_defined_],
+                         "Is from env.   : " + bool_str[sc.is_from_env],
+                         "Is special     : " + bool_str[sc.is_special_] + "\n")
+            if sc.ranges:
+                res += _lines("Ranges:", ranges_str + "\n")
+            res += _lines("Prompts:",
+                          prompts_str,
+                          "Default values:",
+                          defaults_str,
+                          "Selects:",
+                          selects_str,
+                          "Reverse (select-related) dependencies:",
+                          " (no reverse dependencies)" if sc.rev_dep == "n"
+                            else " " + self._expr_val_str(sc.rev_dep),
+                          "Additional dependencies from enclosing menus "
+                            "and ifs:",
+                          additional_deps_str,
+                          "Locations: " + locations_str)
 
             return res
 
@@ -1764,616 +1695,220 @@ error, and you should e-mail kconfiglib at gmail.com.
         # Choice-specific stuff
         #
 
-        # Build name string (for named choices)
-        if sc.name is None:
-            name_str = "(no name)"
-        else:
-            name_str = sc.name
-
         # Build selected symbol string
         sel = sc.get_selection()
-        if sel is None:
-            sel_str = "(no selection)"
-        else:
-            sel_str = sel.name
-
-        # Build mode string
-        mode_str = s(sc.get_mode())
+        sel_str = "(no selection)" if sel is None else sel.name
 
         # Build default values string
-        if sc.def_exprs == []:
+        if not sc.def_exprs:
             defaults_str = " (no default values)"
         else:
             defaults_str_rows = []
-
-            for (sym, cond_expr) in sc.orig_def_exprs:
+            for sym, cond_expr in sc.orig_def_exprs:
                 if cond_expr is None:
                     defaults_str_rows.append(" {0}".format(sym.name))
                 else:
                     defaults_str_rows.append(" {0} if ".format(sym.name) +
                                              self._expr_val_str(cond_expr))
-
             defaults_str = "\n".join(defaults_str_rows)
 
         # Build contained symbols string
         names = [sym.name for sym in sc.get_symbols()]
+        syms_string = " ".join(names) if names else "(empty)"
+
+        return _lines("Choice",
+                      "Name (for named choices): " +
+                        ("(no name)" if sc.name is None else sc.name),
+                      "Type            : " + typename[sc.type],
+                      "Selected symbol : " + sel_str,
+                      "User value      : " + user_val_str,
+                      "Mode            : " + s(sc.get_mode()),
+                      "Visibility      : " + s(sc.get_visibility()),
+                      "Optional        : " + bool_str[sc.optional],
+                      "Prompts:",
+                      prompts_str,
+                      "Defaults:",
+                      defaults_str,
+                      "Choice symbols:",
+                      " " + syms_string,
+                      "Additional dependencies from enclosing menus and "
+                        "ifs:",
+                      additional_deps_str,
+                      "Locations: " + locations_str)
 
-        if names == []:
-            syms_string = "(empty)"
-        else:
-            syms_string = " ".join(names)
-
-        return _sep_lines("Choice",
-                          "Name (for named choices): " + name_str,
-                          "Type            : " + typename[sc.type],
-                          "Selected symbol : " + sel_str,
-                          "User value      : " + user_value_str,
-                          "Mode            : " + mode_str,
-                          "Visibility      : " + visibility_str,
-                          "Optional        : " + bool_str[sc.optional],
-                          "Prompts:",
-                          prompts_str,
-                          "Defaults:",
-                          defaults_str,
-                          "Choice symbols:",
-                          " " + syms_string,
-                          "Additional dependencies from enclosing menus and if's:",
-                          additional_deps_str,
-                          "Locations: " + locations_str)
+    def _eq_to_sym(self, eq):
+        """_expr_depends_on() helper. For (in)equalities of the form sym = y/m
+        or sym != n, returns sym. For other (in)equalities, returns None."""
+        relation, left, right = eq
+
+        def transform_y_m_n(item):
+            if item is self.y: return "y"
+            if item is self.m: return "m"
+            if item is self.n: return "n"
+            return item
+
+        left = transform_y_m_n(left)
+        right = transform_y_m_n(right)
+
+        # Make sure the symbol (if any) appears to the left
+        if not isinstance(left, Symbol):
+            left, right = right, left
+        if not isinstance(left, Symbol):
+            return None
+        if (relation == EQUAL and (right == "y" or right == "m")) or \
+           (relation == UNEQUAL and right == "n"):
+            return left
+        return None
 
     def _expr_depends_on(self, expr, sym):
         """Reimplementation of expr_depends_symbol() from mconf.c. Used to
-        determine if a submenu should be implicitly created, which influences what
-        items inside choice statements are considered choice items."""
+        determine if a submenu should be implicitly created, which influences
+        what items inside choice statements are considered choice items."""
         if expr is None:
             return False
 
         def rec(expr):
             if isinstance(expr, str):
                 return False
-
             if isinstance(expr, Symbol):
                 return expr is sym
 
             e0 = expr[0]
-
             if e0 == EQUAL or e0 == UNEQUAL:
                 return self._eq_to_sym(expr) is sym
-
             if e0 == AND:
                 for and_expr in expr[1]:
                     if rec(and_expr):
                         return True
-
             return False
 
         return rec(expr)
 
-    def _eq_to_sym(self, eq):
-        """_expr_depends_on() helper. For (in)equalities of the form sym = y/m
-        or sym != n, returns sym. For other (in)equalities, returns None."""
-        relation, left, right = eq
+    def _warn(self, msg, filename=None, linenr=None):
+        """For printing warnings to stderr."""
+        if self.print_warnings:
+            _stderr_msg("warning: " + msg, filename, linenr)
 
-        left  = self._transform_n_m_y(left)
-        right = self._transform_n_m_y(right)
+class Item(object):
 
-        # Make sure the symbol (if any) appears to the left
-        if not isinstance(left, Symbol):
-            left, right = right, left
+    """Base class for symbols and other Kconfig constructs. Subclasses are
+    Symbol, Choice, Menu, and Comment."""
 
-        if not isinstance(left, Symbol):
-            return None
+    def is_symbol(self):
+        """Returns True if the item is a symbol. Short for
+        isinstance(item, kconfiglib.Symbol)."""
+        return isinstance(self, Symbol)
 
-        if (relation == EQUAL   and (right == "m" or right == "y")) or \
-           (relation == UNEQUAL and right == "n"):
-            return left
+    def is_choice(self):
+        """Returns True if the item is a choice. Short for
+        isinstance(item, kconfiglib.Choice)."""
+        return isinstance(self, Choice)
 
-        return None
+    def is_menu(self):
+        """Returns True if the item is a menu. Short for
+        isinstance(item, kconfiglib.Menu)."""
+        return isinstance(self, Menu)
 
-    def _transform_n_m_y(self, item):
-        """_eq_to_sym() helper. Translates the symbols n, m, and y to their
-        string equivalents."""
-        if item is self.n:
-            return "n"
-        if item is self.m:
-            return "m"
-        if item is self.y:
-            return "y"
-        return item
+    def is_comment(self):
+        """Returns True if the item is a comment. Short for
+        isinstance(item, kconfiglib.Comment)."""
+        return isinstance(self, Comment)
 
-    def _warn(self, msg, filename = None, linenr = None):
-        """For printing warnings to stderr."""
-        if self.print_warnings:
-            self._warn_or_undef_assign(msg, WARNING, filename, linenr)
-
-    def _undef_assign(self, msg, filename = None, linenr = None):
-        """For printing informational messages related to assignments
-        to undefined variables to stderr."""
-        if self.print_undef_assign:
-            self._warn_or_undef_assign(msg, UNDEF_ASSIGN, filename, linenr)
-
-    def _warn_or_undef_assign(self, msg, msg_type, filename, linenr):
-        if filename is not None:
-            sys.stderr.write("{0}:".format(_clean_up_path(filename)))
-        if linenr is not None:
-            sys.stderr.write("{0}:".format(linenr))
-
-        if msg_type == WARNING:
-            sys.stderr.write("warning: ")
-        elif msg_type == UNDEF_ASSIGN:
-            sys.stderr.write("info: ")
-        else:
-            _internal_error('Internal error while printing warning: unknown warning type "{0}".'
-                            .format(msg_type))
+class Symbol(Item):
 
-        sys.stderr.write(msg + "\n")
+    """Represents a configuration symbol - e.g. FOO for
 
-def _get_expr_syms(expr):
-    """Returns the set() of symbols appearing in expr."""
-    res = set()
-    if expr is None:
-        return res
+    config FOO
+        ..."""
 
-    def rec(expr):
-        if isinstance(expr, Symbol):
-            res.add(expr)
-            return
+    #
+    # Public interface
+    #
 
-        if isinstance(expr, str):
-            return
+    def get_value(self):
+        """Calculate and return the value of the symbol. See also
+        Symbol.set_user_value()."""
 
-        e0 = expr[0]
+        if self.cached_val is not None:
+            return self.cached_val
 
-        if e0 == OR or e0 == AND:
-            for term in expr[1]:
-                rec(term)
+        # As a quirk of Kconfig, undefined symbols get their name as their
+        # value. This is why things like "FOO = bar" work for seeing if FOO has
+        # the value "bar".
+        if self.type == UNKNOWN:
+            self.cached_val = self.name
+            return self.name
 
-        elif e0 == NOT:
-            rec(expr[1])
+        new_val = default_value[self.type]
+        vis = _get_visibility(self)
 
-        elif e0 == EQUAL or e0 == UNEQUAL:
-            _, v1, v2 = expr
+        # This is easiest to calculate together with the value
+        self.write_to_conf = False
 
-            if isinstance(v1, Symbol):
-                res.add(v1)
+        if self.type == BOOL or self.type == TRISTATE:
+            # The visibility and mode (modules-only or single-selection) of
+            # choice items will be taken into account in _get_visibility()
+            if self.is_choice_symbol_:
+                if vis != "n":
+                    choice = self.parent
+                    mode = choice.get_mode()
 
-            if isinstance(v2, Symbol):
-                res.add(v2)
+                    self.write_to_conf = (mode != "n")
 
-        else:
-            _internal_error("Internal error while fetching symbols from an "
-                            "expression with token stream {0}.".format(expr))
+                    if mode == "y":
+                        if choice.get_selection() is self:
+                            new_val = "y"
+                        else:
+                            new_val = "n"
+                    elif mode == "m":
+                        if self.user_val == "m" or self.user_val == "y":
+                            new_val = "m"
 
-    rec(expr)
-    return res
+            else:
+                # If the symbol is visible and has a user value, use that.
+                # Otherwise, look at defaults.
+                use_defaults = True
 
+                if vis != "n":
+                    self.write_to_conf = True
+                    if self.user_val is not None:
+                        new_val = self.config._eval_min(self.user_val, vis)
+                        use_defaults = False
 
-#
-# Construction of expressions
-#
+                if use_defaults:
+                    for val_expr, cond_expr in self.def_exprs:
+                        cond_eval = self.config._eval_expr(cond_expr)
+                        if cond_eval != "n":
+                            self.write_to_conf = True
+                            new_val = self.config._eval_min(val_expr,
+                                                            cond_eval)
+                            break
 
-# These functions as well as the _eval_min/max() functions above equate
-# None with "y", which is usually what we want, but needs to be kept in
-# mind.
+                # Reverse (select-related) dependencies take precedence
+                rev_dep_val = self.config._eval_expr(self.rev_dep)
+                if rev_dep_val != "n":
+                    self.write_to_conf = True
+                    new_val = self.config._eval_max(new_val, rev_dep_val)
 
-def _make_or(e1, e2):
-    # Perform trivial simplification and avoid None's (which
-    # correspond to y's)
-    if e1 is None or e2 is None or \
-       e1 == "y" or e2 == "y":
-        return "y"
+            # Promote "m" to "y" for booleans
+            if new_val == "m" and self.type == BOOL:
+                new_val = "y"
 
-    if e1 == "n":
-        return e2
+        elif self.type == STRING:
+            use_defaults = True
 
-    if e2 == "n":
-        return e1
+            if vis != "n":
+                self.write_to_conf = True
+                if self.user_val is not None:
+                    new_val = self.user_val
+                    use_defaults = False
 
-    # Prefer to merge/update argument list if possible instead of creating
-    # a new OR node
-
-    if isinstance(e1, tuple) and e1[0] == OR:
-        if isinstance(e2, tuple) and e2[0] == OR:
-            return (OR, e1[1] + e2[1])
-        return (OR, e1[1] + [e2])
-
-    if isinstance(e2, tuple) and e2[0] == OR:
-        return (OR, e2[1] + [e1])
-
-    return (OR, [e1, e2])
-
-# Note: returns None if e1 == e2 == None
-
-def _make_and(e1, e2):
-    if e1 == "n" or e2 == "n":
-        return "n"
-
-    if e1 is None or e1 == "y":
-        return e2
-
-    if e2 is None or e2 == "y":
-        return e1
-
-    # Prefer to merge/update argument list if possible instead of creating
-    # a new AND node
-
-    if isinstance(e1, tuple) and e1[0] == AND:
-        if isinstance(e2, tuple) and e2[0] == AND:
-            return (AND, e1[1] + e2[1])
-        return (AND, e1[1] + [e2])
-
-    if isinstance(e2, tuple) and e2[0] == AND:
-        return (AND, e2[1] + [e1])
-
-    return (AND, [e1, e2])
-
-#
-# Constants and functions related to types, parsing, evaluation and printing,
-# put globally to unclutter the Config class a bit.
-#
-
-# Tokens
-(T_OR, T_AND, T_NOT,
- T_OPEN_PAREN, T_CLOSE_PAREN,
- T_EQUAL, T_UNEQUAL,
- T_MAINMENU, T_MENU, T_ENDMENU,
- T_SOURCE, T_CHOICE, T_ENDCHOICE,
- T_COMMENT, T_CONFIG, T_MENUCONFIG,
- T_HELP, T_IF, T_ENDIF, T_DEPENDS, T_ON,
- T_OPTIONAL, T_PROMPT, T_DEFAULT,
- T_BOOL, T_TRISTATE, T_HEX, T_INT, T_STRING,
- T_DEF_BOOL, T_DEF_TRISTATE,
- T_SELECT, T_RANGE, T_OPTION, T_ENV,
- T_DEFCONFIG_LIST, T_MODULES, T_VISIBLE) = range(0, 38)
-
-# Keyword to token map
-keywords = {
-        "mainmenu"       : T_MAINMENU,
-        "menu"           : T_MENU,
-        "endmenu"        : T_ENDMENU,
-        "endif"          : T_ENDIF,
-        "endchoice"      : T_ENDCHOICE,
-        "source"         : T_SOURCE,
-        "choice"         : T_CHOICE,
-        "config"         : T_CONFIG,
-        "comment"        : T_COMMENT,
-        "menuconfig"     : T_MENUCONFIG,
-        "help"           : T_HELP,
-        "if"             : T_IF,
-        "depends"        : T_DEPENDS,
-        "on"             : T_ON,
-        "optional"       : T_OPTIONAL,
-        "prompt"         : T_PROMPT,
-        "default"        : T_DEFAULT,
-        "bool"           : T_BOOL,
-        "boolean"        : T_BOOL,
-        "tristate"       : T_TRISTATE,
-        "int"            : T_INT,
-        "hex"            : T_HEX,
-        "def_bool"       : T_DEF_BOOL,
-        "def_tristate"   : T_DEF_TRISTATE,
-        "string"         : T_STRING,
-        "select"         : T_SELECT,
-        "range"          : T_RANGE,
-        "option"         : T_OPTION,
-        "env"            : T_ENV,
-        "defconfig_list" : T_DEFCONFIG_LIST,
-        "modules"        : T_MODULES,
-        "visible"        : T_VISIBLE }
-
-# Strings to use for True and False
-bool_str = { False : "false", True : "true" }
-
-# Tokens after which identifier-like lexemes are treated as strings. T_CHOICE
-# is included to avoid symbols being registered for named choices.
-string_lex = frozenset((T_BOOL, T_TRISTATE, T_INT, T_HEX, T_STRING, T_CHOICE,
-                        T_PROMPT, T_MENU, T_COMMENT, T_SOURCE, T_MAINMENU))
-
-# Matches the initial token on a line; see _tokenize().
-initial_token_re = re.compile(r"[^\w]*(\w+)")
-
-# Matches an identifier/keyword optionally preceded by whitespace
-id_keyword_re = re.compile(r"\s*([\w./-]+)")
-
-# Regular expressions for parsing .config files
-set_re   = re.compile(r"CONFIG_(\w+)=(.*)")
-unset_re = re.compile(r"# CONFIG_(\w+) is not set")
-
-# Regular expression for finding $-references to symbols in strings
-sym_ref_re = re.compile(r"\$[A-Za-z_]+")
-
-# Integers representing symbol types
-UNKNOWN, BOOL, TRISTATE, STRING, HEX, INT = range(0, 6)
-
-# Strings to use for types
-typename = {
-        UNKNOWN  : "unknown",
-        BOOL     : "bool",
-        TRISTATE : "tristate",
-        STRING   : "string",
-        HEX      : "hex",
-        INT      : "int" }
-
-# Token to type mapping
-token_to_type = { T_BOOL     : BOOL,
-                  T_TRISTATE : TRISTATE,
-                  T_STRING   : STRING,
-                  T_INT      : INT,
-                  T_HEX      : HEX }
-
-# Default values for symbols of different types (the value the symbol gets if
-# it is not assigned a user value and none of its 'default' clauses kick in)
-default_value = { BOOL     : "n",
-                  TRISTATE : "n",
-                  STRING   : "",
-                  INT      : "",
-                  HEX      : "" }
-
-# Indicates that no item is selected in a choice statement
-NO_SELECTION = 0
-
-# Integers representing expression types
-OR, AND, NOT, EQUAL, UNEQUAL = range(0, 5)
-
-# Map from tristate values to integers
-tri_to_int = { "n" : 0, "m" : 1, "y" : 2 }
-
-# Printing-related stuff
-
-op_to_str = { AND     : " && ",
-              OR      : " || ",
-              EQUAL   : " = ",
-              UNEQUAL : " != " }
-
-precedence = { OR : 0, AND : 1, NOT : 2 }
-
-# Types of informational messages
-WARNING = 0
-UNDEF_ASSIGN = 1
-
-def _intersperse(lst, op):
-    """_expr_to_str() helper. Gets the string representation of each expression in lst
-    and produces a list where op has been inserted between the elements."""
-    if lst == []:
-        return ""
-
-    res = []
-
-    def handle_sub_expr(expr):
-        no_parens = isinstance(expr, (str, Symbol)) or \
-                    expr[0] in (EQUAL, UNEQUAL) or \
-                    precedence[op] <= precedence[expr[0]]
-        if not no_parens:
-            res.append("(")
-        res.extend(_expr_to_str_rec(expr))
-        if not no_parens:
-            res.append(")")
-
-    op_str = op_to_str[op]
-
-    handle_sub_expr(lst[0])
-    for expr in lst[1:]:
-        res.append(op_str)
-        handle_sub_expr(expr)
-
-    return res
-
-def _expr_to_str(expr):
-    s = "".join(_expr_to_str_rec(expr))
-    return s
-
-def _sym_str_string(sym_or_str):
-    if isinstance(sym_or_str, str):
-        return '"{0}"'.format(sym_or_str)
-    return sym_or_str.name
-
-def _expr_to_str_rec(expr):
-    if expr is None:
-        return [""]
-
-    if isinstance(expr, (Symbol, str)):
-        return [_sym_str_string(expr)]
-
-    e0 = expr[0]
-
-    if e0 == OR or e0 == AND:
-        return _intersperse(expr[1], expr[0])
-
-    if e0 == NOT:
-        need_parens = not isinstance(expr[1], (str, Symbol))
-
-        res = ["!"]
-        if need_parens:
-            res.append("(")
-        res.extend(_expr_to_str_rec(expr[1]))
-        if need_parens:
-            res.append(")")
-        return res
-
-    if e0 == EQUAL or e0 == UNEQUAL:
-        return [_sym_str_string(expr[1]),
-                op_to_str[expr[0]],
-                _sym_str_string(expr[2])]
-
-class _Block:
-
-    """Represents a list of items (symbols, menus, choice statements and
-    comments) appearing at the top-level of a file or witin a menu, choice or
-    if statement."""
-
-    def __init__(self):
-        self.items = []
-
-    def get_items(self):
-        return self.items
-
-    def add_item(self, item):
-        self.items.append(item)
-
-    def _make_conf(self):
-        # Collect the substrings in a list and later use join() instead of +=
-        # to build the final .config contents. With older Python versions, this
-        # yields linear instead of quadratic complexity.
-        strings = []
-        for item in self.items:
-            strings.extend(item._make_conf())
-
-        return strings
-
-    def add_depend_expr(self, expr):
-        for item in self.items:
-            item.add_depend_expr(expr)
-
-class Item():
-
-    """Base class for symbols and other Kconfig constructs. Subclasses are
-    Symbol, Choice, Menu, and Comment."""
-
-    def is_symbol(self):
-        """Returns True if the item is a symbol, otherwise False. Short for
-        isinstance(item, kconfiglib.Symbol)."""
-        return isinstance(self, Symbol)
-
-    def is_choice(self):
-        """Returns True if the item is a choice, otherwise False. Short for
-        isinstance(item, kconfiglib.Choice)."""
-        return isinstance(self, Choice)
-
-    def is_menu(self):
-        """Returns True if the item is a menu, otherwise False. Short for
-        isinstance(item, kconfiglib.Menu)."""
-        return isinstance(self, Menu)
-
-    def is_comment(self):
-        """Returns True if the item is a comment, otherwise False. Short for
-        isinstance(item, kconfiglib.Comment)."""
-        return isinstance(self, Comment)
-
-class _HasVisibility():
-
-    """Base class for elements that have a "visibility" that acts as an upper
-    limit on the values a user can set for them. Subclasses are Symbol and
-    Choice (which supply some of the attributes)."""
-
-    def __init__(self):
-        self.cached_visibility = None
-        self.prompts = []
-
-    def _invalidate(self):
-        self.cached_visibility = None
-
-    def _get_visibility(self):
-        if self.cached_visibility is None:
-            vis = "n"
-            for (prompt, cond_expr) in self.prompts:
-                vis = self.config._eval_max(vis, cond_expr)
-
-            if isinstance(self, Symbol) and self.is_choice_symbol_:
-                vis = self.config._eval_min(vis, self.parent._get_visibility())
-
-            # Promote "m" to "y" if we're dealing with a non-tristate
-            if vis == "m" and self.type != TRISTATE:
-                vis = "y"
-
-            self.cached_visibility = vis
-
-        return self.cached_visibility
-
-class Symbol(Item, _HasVisibility):
-
-    """Represents a configuration symbol - e.g. FOO for
-
-    config FOO
-        ..."""
-
-    #
-    # Public interface
-    #
-
-    def get_value(self):
-        """Calculate and return the value of the symbol. See also
-        Symbol.set_user_value()."""
-
-        if self.cached_value is not None:
-            return self.cached_value
-
-        self.write_to_conf = False
-
-        # As a quirk of Kconfig, undefined symbols get their name as their
-        # value. This is why things like "FOO = bar" work for seeing if FOO has
-        # the value "bar".
-        if self.type == UNKNOWN:
-            self.cached_value = self.name
-            return self.name
-
-        new_val = default_value[self.type]
-
-        vis = self._get_visibility()
-
-        if self.type == BOOL or self.type == TRISTATE:
-            # The visibility and mode (modules-only or single-selection) of
-            # choice items will be taken into account in self._get_visibility()
-
-            if self.is_choice_symbol_:
-                if vis != "n":
-                    choice = self.parent
-                    mode = choice.get_mode()
-
-                    self.write_to_conf = (mode != "n")
-
-                    if mode == "y":
-                        new_val = "y" if (choice.get_selection() is self) else "n"
-                    elif mode == "m":
-                        if self.user_val == "m" or self.user_val == "y":
-                            new_val = "m"
-
-            else:
-                use_defaults = True
-
-                if vis != "n":
-                    # If the symbol is visible and has a user value, use that.
-                    # Otherwise, look at defaults.
-                    self.write_to_conf = True
-
-                    if self.user_val is not None:
-                        new_val = self.config._eval_min(self.user_val, vis)
-                        use_defaults = False
-
-                if use_defaults:
-                    for (val_expr, cond_expr) in self.def_exprs:
-                        cond_eval = self.config._eval_expr(cond_expr)
-
-                        if cond_eval != "n":
-                            self.write_to_conf = True
-                            new_val = self.config._eval_min(val_expr, cond_eval)
-                            break
-
-                # Reverse dependencies take precedence
-                rev_dep_val = self.config._eval_expr(self.rev_dep)
-
-                if rev_dep_val != "n":
-                    self.write_to_conf = True
-                    new_val = self.config._eval_max(new_val, rev_dep_val)
-
-            # Promote "m" to "y" for booleans
-            if new_val == "m" and self.type == BOOL:
-                new_val = "y"
-
-        elif self.type == STRING:
-            use_defaults = True
-
-            if vis != "n":
-                self.write_to_conf = True
-                if self.user_val is not None:
-                    new_val = self.user_val
-                    use_defaults = False
-
-            if use_defaults:
-                for (val_expr, cond_expr) in self.def_exprs:
-                    if self.config._eval_expr(cond_expr) != "n":
-                        self.write_to_conf = True
-                        new_val = self.config._get_str_value(val_expr)
-                        break
+            if use_defaults:
+                for val_expr, cond_expr in self.def_exprs:
+                    if self.config._eval_expr(cond_expr) != "n":
+                        self.write_to_conf = True
+                        new_val = _str_val(val_expr)
+                        break
 
         elif self.type == HEX or self.type == INT:
             has_active_range = False
@@ -2387,9 +1922,8 @@ class Symbol(Item, _HasVisibility):
                 if self.config._eval_expr(cond_expr) != "n":
                     has_active_range = True
 
-                    low_str = self.config._get_str_value(l)
-                    high_str = self.config._get_str_value(h)
-
+                    low_str = _str_val(l)
+                    high_str = _str_val(h)
                     low = int(low_str, base) if \
                       _is_base_n(low_str, base) else 0
                     high = int(high_str, base) if \
@@ -2413,7 +1947,7 @@ class Symbol(Item, _HasVisibility):
                     new_val = self.user_val
 
             if use_defaults:
-                for (val_expr, cond_expr) in self.def_exprs:
+                for val_expr, cond_expr in self.def_exprs:
                     if self.config._eval_expr(cond_expr) != "n":
                         self.write_to_conf = True
 
@@ -2422,7 +1956,7 @@ class Symbol(Item, _HasVisibility):
                         # to the range, and the output has "0x" as appropriate
                         # for the type.
 
-                        new_val = self.config._get_str_value(val_expr)
+                        new_val = _str_val(val_expr)
 
                         if _is_base_n(new_val, base):
                             new_val_num = int(new_val, base)
@@ -2443,11 +1977,10 @@ class Symbol(Item, _HasVisibility):
                     # If no user value or default kicks in but the hex/int has
                     # an active range, then the low end of the range is used,
                     # provided it's > 0, with "0x" prepended as appropriate.
-
                     if has_active_range and low > 0:
                         new_val = (hex(low) if self.type == HEX else str(low))
 
-        self.cached_value = new_val
+        self.cached_val = new_val
         return new_val
 
     def set_user_value(self, v):
@@ -2493,8 +2026,8 @@ class Symbol(Item, _HasVisibility):
 
     def get_user_value(self):
         """Returns the value assigned to the symbol in a .config or via
-        Symbol.set_user_value() (provided the value was valid for the type of the
-        symbol). Returns None in case of no user value."""
+        Symbol.set_user_value() (provided the value was valid for the type of
+        the symbol). Returns None in case of no user value."""
         return self.user_val
 
     def get_name(self):
@@ -2516,9 +2049,10 @@ class Symbol(Item, _HasVisibility):
         cannot be modified (see is_modifiable()), returns None.
 
         Otherwise, returns the highest value the symbol can be set to with
-        Symbol.set_user_value() (that will not be truncated): one of "m" or "y",
-        arranged from lowest to highest. This corresponds to the highest value
-        the symbol could be given in e.g. the 'make menuconfig' interface.
+        Symbol.set_user_value() (that will not be truncated): one of "m" or
+        "y", arranged from lowest to highest. This corresponds to the highest
+        value the symbol could be given in e.g. the 'make menuconfig'
+        interface.
 
         See also the tri_less*() and tri_greater*() functions, which could come
         in handy."""
@@ -2528,7 +2062,7 @@ class Symbol(Item, _HasVisibility):
         # A bool selected to "m" gets promoted to "y"
         if self.type == BOOL and rev_dep == "m":
             rev_dep = "y"
-        vis = self._get_visibility()
+        vis = _get_visibility(self)
         if (tri_to_int[vis] - tri_to_int[rev_dep]) > 0:
             return vis
         return None
@@ -2538,9 +2072,10 @@ class Symbol(Item, _HasVisibility):
         cannot be modified (see is_modifiable()), returns None.
 
         Otherwise, returns the lowest value the symbol can be set to with
-        Symbol.set_user_value() (that will not be truncated): one of "n" or "m",
-        arranged from lowest to highest. This corresponds to the lowest value
-        the symbol could be given in e.g. the 'make menuconfig' interface.
+        Symbol.set_user_value() (that will not be truncated): one of "n" or
+        "m", arranged from lowest to highest. This corresponds to the lowest
+        value the symbol could be given in e.g. the 'make menuconfig'
+        interface.
 
         See also the tri_less*() and tri_greater*() functions, which could come
         in handy."""
@@ -2550,7 +2085,7 @@ class Symbol(Item, _HasVisibility):
         # A bool selected to "m" gets promoted to "y"
         if self.type == BOOL and rev_dep == "m":
             rev_dep = "y"
-        if (tri_to_int[self._get_visibility()] - tri_to_int[rev_dep]) > 0:
+        if (tri_to_int[_get_visibility(self)] - tri_to_int[rev_dep]) > 0:
             return rev_dep
         return None
 
@@ -2574,7 +2109,7 @@ class Symbol(Item, _HasVisibility):
         if self.type == BOOL and rev_dep == "m":
             rev_dep = "y"
         res = ["n", "m", "y"][tri_to_int[rev_dep] :
-                              tri_to_int[self._get_visibility()] + 1]
+                              tri_to_int[_get_visibility(self)] + 1]
         return res if len(res) > 1 else []
 
     def get_type(self):
@@ -2628,7 +2163,7 @@ class Symbol(Item, _HasVisibility):
 
         You should probably look at get_lower/upper_bound(),
         get_assignable_values() and is_modifiable() before using this."""
-        return self._get_visibility()
+        return _get_visibility(self)
 
     def get_parent(self):
         """Returns the menu or choice statement that contains the symbol, or
@@ -2637,7 +2172,7 @@ class Symbol(Item, _HasVisibility):
         representation."""
         return self.parent
 
-    def get_referenced_symbols(self, refs_from_enclosing = False):
+    def get_referenced_symbols(self, refs_from_enclosing=False):
         """Returns the set() of all symbols referenced by this symbol. For
         example, the symbol defined by
 
@@ -2651,9 +2186,10 @@ class Symbol(Item, _HasVisibility):
         references the symbols A through G.
 
         refs_from_enclosing (default: False) -- If True, the symbols
-                            referenced by enclosing menus and if's will be
+                            referenced by enclosing menus and ifs will be
                             included in the result."""
-        return self.all_referenced_syms if refs_from_enclosing else self.referenced_syms
+        return self.all_referenced_syms if refs_from_enclosing else \
+               self.referenced_syms
 
     def get_selected_symbols(self):
         """Returns the set() of all symbols X for which this symbol has a
@@ -2713,7 +2249,7 @@ class Symbol(Item, _HasVisibility):
 
     def is_modifiable(self):
         """Returns True if the value of the symbol could be modified by calling
-        Symbol.set_user_value() and False otherwise.
+        Symbol.set_user_value().
 
         For bools and tristates, this corresponds to the symbol being visible
         in the 'make menuconfig' interface and not already being pinned to a
@@ -2728,43 +2264,45 @@ class Symbol(Item, _HasVisibility):
             # A bool selected to "m" gets promoted to "y"
             if self.type == BOOL and rev_dep == "m":
                 rev_dep = "y"
-            return (tri_to_int[self._get_visibility()] -
+            return (tri_to_int[_get_visibility(self)] -
                     tri_to_int[rev_dep]) > 0
-        return self._get_visibility() != "n"
+        return _get_visibility(self) != "n"
 
     def is_defined(self):
         """Returns False if the symbol is referred to in the Kconfig but never
-        actually defined, otherwise True."""
+        actually defined."""
         return self.is_defined_
 
     def is_special(self):
         """Returns True if the symbol is one of the special symbols n, m, y, or
-        UNAME_RELEASE, or gets its value from the environment. Otherwise,
-        returns False."""
+        UNAME_RELEASE, or gets its value from the environment."""
         return self.is_special_
 
     def is_from_environment(self):
-        """Returns True if the symbol gets its value from the environment.
-        Otherwise, returns False."""
+        """Returns True if the symbol gets its value from the environment."""
         return self.is_from_env
 
     def has_ranges(self):
         """Returns True if the symbol is of type INT or HEX and has ranges that
-        limits what values it can take on, otherwise False."""
-        return self.ranges != []
+        limit what values it can take on."""
+        return bool(self.ranges)
 
     def is_choice_symbol(self):
         """Returns True if the symbol is in a choice statement and is an actual
-        choice symbol (see Choice.get_symbols()); otherwise, returns
-        False."""
+        choice symbol (see Choice.get_symbols())."""
         return self.is_choice_symbol_
 
     def is_choice_selection(self):
         """Returns True if the symbol is contained in a choice statement and is
-        the selected item, otherwise False. Equivalent to 'sym.is_choice_symbol()
-        and sym.get_parent().get_selection() is sym'."""
+        the selected item. Equivalent to
+
+        sym.is_choice_symbol() and sym.get_parent().get_selection() is sym"""
         return self.is_choice_symbol_ and self.parent.get_selection() is self
 
+    def is_allnoconfig_y(self):
+        """Returns True if the symbol has the 'allnoconfig_y' option set."""
+        return self.allnoconfig_y
+
     def __str__(self):
         """Returns a string containing various information about the symbol."""
         return self.config._get_sym_or_choice_str(self)
@@ -2777,8 +2315,8 @@ class Symbol(Item, _HasVisibility):
         """Symbol constructor -- not intended to be called directly by
         kconfiglib clients."""
 
-        # Set default values
-        _HasVisibility.__init__(self)
+        self.prompts = []
+        self.cached_visibility = None
 
         self.config = None
 
@@ -2791,13 +2329,13 @@ class Symbol(Item, _HasVisibility):
         self.rev_dep = "n"
 
         # The prompt, default value and select conditions without any
-        # dependencies from menus or if's propagated to them
+        # dependencies from menus or ifs propagated to them
 
         self.orig_prompts = []
         self.orig_def_exprs = []
         self.orig_selects = []
 
-        # Dependencies inherited from containing menus and if's
+        # Dependencies inherited from containing menus and ifs
         self.deps_from_containing = None
 
         self.help = None
@@ -2811,7 +2349,7 @@ class Symbol(Item, _HasVisibility):
         self.selected_syms = set()
 
         # Like 'referenced_syms', but includes symbols from
-        # dependencies inherited from enclosing menus and if's
+        # dependencies inherited from enclosing menus and ifs
         self.all_referenced_syms = set()
 
         # This is set to True for "actual" choice symbols. See
@@ -2836,13 +2374,14 @@ class Symbol(Item, _HasVisibility):
         self.write_to_conf = False
 
         # Caches the calculated value
-        self.cached_value = None
+        self.cached_val = None
 
-        # Note: An instance variable 'self.dep' gets set on the Symbol in
-        # Config._build_dep(), linking the symbol to the symbols that
-        # immediately depend on it (in a caching/invalidation sense). The total
-        # set of dependent symbols for the symbol (the transitive closure) is
-        # calculated on an as-needed basis in _get_dependent().
+        # Populated in Config._build_dep() after parsing. Links the symbol to
+        # the symbols that immediately depend on it (in a caching/invalidation
+        # sense). The total set of dependent symbols for the symbol (the
+        # transitive closure) is calculated on an as-needed basis in
+        # _get_dependent().
+        self.dep = set()
 
         # Caches the total list of dependent symbols. Calculated in
         # _get_dependent().
@@ -2854,7 +2393,7 @@ class Symbol(Item, _HasVisibility):
 
         # Does the symbol get its value in some special way, e.g. from the
         # environment or by being one of the special symbols n, m, and y? If
-        # so, the value is stored in self.cached_value, which is never
+        # so, the value is stored in self.cached_val, which is never
         # invalidated. The trailing underscore avoids a collision with
         # is_special().
         self.is_special_ = False
@@ -2862,6 +2401,9 @@ class Symbol(Item, _HasVisibility):
         # Does the symbol get its value from the environment?
         self.is_from_env = False
 
+        # Does the symbol have the 'allnoconfig_y' option set?
+        self.allnoconfig_y = False
+
     def _invalidate(self):
         if self.is_special_:
             return
@@ -2869,10 +2411,9 @@ class Symbol(Item, _HasVisibility):
         if self.is_choice_symbol_:
             self.parent._invalidate()
 
-        _HasVisibility._invalidate(self)
-
+        self.cached_val = None
+        self.cached_visibility = None
         self.write_to_conf = False
-        self.cached_value = None
 
     def _invalidate_dependent(self):
         for sym in self._get_dependent():
@@ -2898,34 +2439,30 @@ class Symbol(Item, _HasVisibility):
                 self.config._warn('attempt to assign the value "{0}" to the '
                                   'special symbol {1}. Assignment ignored.'
                                   .format(v, self.name))
-
             return
 
-
         if not self.is_defined_:
             filename, linenr = self.ref_locations[0]
-
-            self.config._undef_assign('attempt to assign the value "{0}" to {1}, '
-                                      "which is referenced at {2}:{3} but never "
-                                      "defined. Assignment ignored."
-                                      .format(v, self.name, filename, linenr))
+            if self.config.print_undef_assign:
+                _stderr_msg('note: attempt to assign the value "{0}" to {1}, '
+                            "which is referenced at {2}:{3} but never "
+                            "defined. Assignment ignored."
+                            .format(v, self.name, filename, linenr))
             return
 
         # Check if the value is valid for our type
-
-        if not (( self.type == BOOL     and (v == "n" or v == "y")    ) or
-                ( self.type == TRISTATE and (v == "n" or v == "m" or
-                                             v == "y")                ) or
-                ( self.type == STRING                                 ) or
-                ( self.type == INT      and _is_base_n(v, 10)         ) or
-                ( self.type == HEX      and _is_base_n(v, 16)         )):
-
-            self.config._warn('the value "{0}" is invalid for {1}, which has type {2}. '
-                              "Assignment ignored."
+        if not ((self.type == BOOL     and (v == "y" or v == "n")   ) or
+                (self.type == TRISTATE and (v == "y" or v == "m" or
+                                            v == "n")               ) or
+                (self.type == STRING                                ) or
+                (self.type == INT      and _is_base_n(v, 10)        ) or
+                (self.type == HEX      and _is_base_n(v, 16)        )):
+            self.config._warn('the value "{0}" is invalid for {1}, which has '
+                              "type {2}. Assignment ignored."
                               .format(v, self.name, typename[self.type]))
             return
 
-        if self.prompts == [] and not suppress_load_warnings:
+        if not self.prompts and not suppress_load_warnings:
             self.config._warn('assigning "{0}" to the symbol {1} which '
                               'lacks prompts and thus has visibility "n". '
                               'The assignment will have no effect.'
@@ -2962,22 +2499,21 @@ class Symbol(Item, _HasVisibility):
             return []
 
         if self.type == BOOL or self.type == TRISTATE:
-            if val == "m" or val == "y":
+            if val == "y" or val == "m":
                 return ["CONFIG_{0}={1}".format(self.name, val)]
             return ["# CONFIG_{0} is not set".format(self.name)]
 
-        elif self.type == STRING:
+        if self.type == INT or self.type == HEX:
+            return ["CONFIG_{0}={1}".format(self.name, val)]
+
+        if self.type == STRING:
             # Escape \ and "
             return ['CONFIG_{0}="{1}"'
                     .format(self.name,
                             val.replace("\\", "\\\\").replace('"', '\\"'))]
 
-        elif self.type == INT or self.type == HEX:
-            return ["CONFIG_{0}={1}".format(self.name, val)]
-
-        else:
-            _internal_error('Internal error while creating .config: unknown type "{0}".'
-                            .format(self.type))
+        _internal_error("Internal error while creating .config: unknown "
+                        'type "{0}".'.format(self.type))
 
     def _get_dependent(self):
         """Returns the set of symbols that should be invalidated if the value
@@ -3012,15 +2548,16 @@ class Symbol(Item, _HasVisibility):
     def _has_auto_menu_dep_on(self, on):
         """See Choice._determine_actual_symbols()."""
         if not isinstance(self.parent, Choice):
-            _internal_error("Attempt to determine auto menu dependency for symbol ouside of choice.")
+            _internal_error("Attempt to determine auto menu dependency for "
+                            "symbol ouside of choice.")
 
-        if self.prompts == []:
+        if not self.prompts:
             # If we have no prompt, use the menu dependencies instead (what was
             # specified with 'depends on')
             return self.menu_dep is not None and \
                    self.config._expr_depends_on(self.menu_dep, on)
 
-        for (_, cond_expr) in self.prompts:
+        for _, cond_expr in self.prompts:
             if self.config._expr_depends_on(cond_expr, on):
                 return True
 
@@ -3048,7 +2585,7 @@ class Menu(Item):
         condition. "y" if the menu has no 'visible if' condition."""
         return self.config._eval_expr(self.visible_if_expr)
 
-    def get_items(self, recursive = False):
+    def get_items(self, recursive=False):
         """Returns a list containing the items (symbols, menus, choice
         statements and comments) in in the menu, in the same order that the
         items appear within the menu.
@@ -3058,10 +2595,10 @@ class Menu(Item):
                                       recursively (preorder)."""
 
         if not recursive:
-            return self.block.get_items()
+            return self.block
 
         res = []
-        for item in self.block.get_items():
+        for item in self.block:
             res.append(item)
             if isinstance(item, Menu):
                 res.extend(item.get_items(True))
@@ -3069,7 +2606,7 @@ class Menu(Item):
                 res.extend(item.get_items())
         return res
 
-    def get_symbols(self, recursive = False):
+    def get_symbols(self, recursive=False):
         """Returns a list containing the symbols in the menu, in the same order
         that they appear within the menu.
 
@@ -3077,7 +2614,8 @@ class Menu(Item):
                                       the menu should be included
                                       recursively."""
 
-        return [item for item in self.get_items(recursive) if isinstance(item, Symbol)]
+        return [item for item in self.get_items(recursive) if
+                isinstance(item, Symbol)]
 
     def get_title(self):
         """Returns the title text of the menu."""
@@ -3090,9 +2628,10 @@ class Menu(Item):
         representation."""
         return self.parent
 
-    def get_referenced_symbols(self, refs_from_enclosing = False):
+    def get_referenced_symbols(self, refs_from_enclosing=False):
         """See Symbol.get_referenced_symbols()."""
-        return self.all_referenced_syms if refs_from_enclosing else self.referenced_syms
+        return self.all_referenced_syms if refs_from_enclosing else \
+               self.referenced_syms
 
     def get_location(self):
         """Returns the location of the menu as a (filename, linenr) tuple,
@@ -3106,16 +2645,18 @@ class Menu(Item):
         visible_if_str = self.config._expr_val_str(self.visible_if_expr,
                                                    "(no dependencies)")
 
-        additional_deps_str = " " + self.config._expr_val_str(self.deps_from_containing,
-                                                              "(no additional dependencies)")
+        additional_deps_str = " " + \
+          self.config._expr_val_str(self.deps_from_containing,
+                                    "(no additional dependencies)")
 
-        return _sep_lines("Menu",
-                          "Title                     : " + self.title,
-                          "'depends on' dependencies : " + depends_on_str,
-                          "'visible if' dependencies : " + visible_if_str,
-                          "Additional dependencies from enclosing menus and if's:",
-                          additional_deps_str,
-                          "Location: {0}:{1}".format(self.filename, self.linenr))
+        return _lines("Menu",
+                      "Title                     : " + self.title,
+                      "'depends on' dependencies : " + depends_on_str,
+                      "'visible if' dependencies : " + visible_if_str,
+                      "Additional dependencies from enclosing menus and "
+                        "ifs:",
+                      additional_deps_str,
+                      "Location: {0}:{1}".format(self.filename, self.linenr))
 
     #
     # Private methods
@@ -3133,10 +2674,10 @@ class Menu(Item):
         self.dep_expr = None
 
         # Dependency expression without dependencies from enclosing menus and
-        # if's propagated
+        # ifs propagated
         self.orig_deps = None
 
-        # Dependencies inherited from containing menus and if's
+        # Dependencies inherited from containing menus and ifs
         self.deps_from_containing = None
 
         # The 'visible if' expression
@@ -3147,21 +2688,21 @@ class Menu(Item):
         self.referenced_syms = set()
 
         # Like 'referenced_syms', but includes symbols from
-        # dependencies inherited from enclosing menus and if's
+        # dependencies inherited from enclosing menus and ifs
         self.all_referenced_syms = None
 
         self.filename = None
         self.linenr = None
 
     def _make_conf(self):
-        item_conf = self.block._make_conf()
+        item_conf = _make_block_conf(self.block)
 
         if self.config._eval_expr(self.dep_expr) != "n" and \
            self.config._eval_expr(self.visible_if_expr) != "n":
             return ["\n#\n# {0}\n#".format(self.title)] + item_conf
         return item_conf
 
-class Choice(Item, _HasVisibility):
+class Choice(Item):
 
     """Represents a choice statement. A choice can be in one of three modes:
 
@@ -3199,8 +2740,7 @@ class Choice(Item, _HasVisibility):
             return self._cache_ret(None)
 
         # User choice available?
-        if self.user_val is not None and \
-           self.user_val._get_visibility() == "y":
+        if self.user_val is not None and _get_visibility(self.user_val) == "y":
             return self._cache_ret(self.user_val)
 
         if self.optional:
@@ -3212,10 +2752,10 @@ class Choice(Item, _HasVisibility):
         """Like Choice.get_selection(), but acts as if no symbol has been
         selected by the user and no 'optional' flag is in effect."""
 
-        if self.actual_symbols == []:
+        if not self.actual_symbols:
             return None
 
-        for (symbol, cond_expr) in self.def_exprs:
+        for symbol, cond_expr in self.def_exprs:
             if self.config._eval_expr(cond_expr) != "n":
                 chosen_symbol = symbol
                 break
@@ -3223,11 +2763,11 @@ class Choice(Item, _HasVisibility):
             chosen_symbol = self.actual_symbols[0]
 
         # Is the chosen symbol visible?
-        if chosen_symbol._get_visibility() != "n":
+        if _get_visibility(chosen_symbol) != "n":
             return chosen_symbol
         # Otherwise, pick the first visible symbol
         for sym in self.actual_symbols:
-            if sym._get_visibility() != "n":
+            if _get_visibility(sym) != "n":
                 return sym
         return None
 
@@ -3271,7 +2811,7 @@ class Choice(Item, _HasVisibility):
         the configuration ("items" instead of "symbols" since choices and
         comments might appear within choices. This only happens in one place as
         of Linux 3.7.0-rc8, in drivers/usb/gadget/Kconfig)."""
-        return self.block.get_items()
+        return self.block
 
     def get_symbols(self):
         """Returns a list containing the choice's symbols.
@@ -3297,9 +2837,10 @@ class Choice(Item, _HasVisibility):
         representation."""
         return self.parent
 
-    def get_referenced_symbols(self, refs_from_enclosing = False):
+    def get_referenced_symbols(self, refs_from_enclosing=False):
         """See Symbol.get_referenced_symbols()."""
-        return self.all_referenced_syms if refs_from_enclosing else self.referenced_syms
+        return self.all_referenced_syms if refs_from_enclosing else \
+               self.referenced_syms
 
     def get_def_locations(self):
         """Returns a list of (filename, linenr) tuples, where filename (string)
@@ -3314,14 +2855,14 @@ class Choice(Item, _HasVisibility):
         "y". This acts as an upper limit on the mode of the choice (though bool
         choices can only have the mode "y"). See the class documentation for an
         explanation of modes."""
-        return self._get_visibility()
+        return _get_visibility(self)
 
     def get_mode(self):
         """Returns the mode of the choice. See the class documentation for
         an explanation of modes."""
         minimum_mode = "n" if self.optional else "m"
         mode = self.user_mode if self.user_mode is not None else minimum_mode
-        mode = self.config._eval_min(mode, self._get_visibility())
+        mode = self.config._eval_min(mode, _get_visibility(self))
 
         # Promote "m" to "y" for boolean choices
         if mode == "m" and self.type == BOOL:
@@ -3330,8 +2871,8 @@ class Choice(Item, _HasVisibility):
         return mode
 
     def is_optional(self):
-        """Returns True if the symbol has the optional flag set (and so will default
-        to "n" mode). Otherwise, returns False."""
+        """Returns True if the choice has the 'optional' flag set (and so will
+        default to "n" mode)."""
         return self.optional
 
     def __str__(self):
@@ -3347,7 +2888,8 @@ class Choice(Item, _HasVisibility):
         """Choice constructor -- not intended to be called directly by
         kconfiglib clients."""
 
-        _HasVisibility.__init__(self)
+        self.prompts = []
+        self.cached_visibility = None
 
         self.config = None
 
@@ -3360,18 +2902,18 @@ class Choice(Item, _HasVisibility):
         self.block = None
 
         # The prompts and default values without any dependencies from
-        # enclosing menus or if's propagated
+        # enclosing menus or ifs propagated
 
         self.orig_prompts = []
         self.orig_def_exprs = []
 
-        # Dependencies inherited from containing menus and if's
+        # Dependencies inherited from containing menus and ifs
         self.deps_from_containing = None
 
         # We need to filter out symbols that appear within the choice block but
         # are not considered choice items (see
-        # Choice._determine_actual_symbols()) This list holds the "actual" choice
-        # items.
+        # Choice._determine_actual_symbols()) This list holds the "actual"
+        # choice items.
         self.actual_symbols = []
 
         # The set of symbols referenced by this choice (see
@@ -3379,7 +2921,7 @@ class Choice(Item, _HasVisibility):
         self.referenced_syms = set()
 
         # Like 'referenced_syms', but includes symbols from
-        # dependencies inherited from enclosing menus and if's
+        # dependencies inherited from enclosing menus and ifs
         self.all_referenced_syms = set()
 
         # See Choice.get_def_locations()
@@ -3392,13 +2934,14 @@ class Choice(Item, _HasVisibility):
 
     def _determine_actual_symbols(self):
         """If a symbol's visibility depends on the preceding symbol within a
-        choice, it is no longer viewed as a choice item (quite possibly a bug,
-        but some things consciously use it.. ugh. It stems from automatic
-        submenu creation). In addition, it's possible to have choices and
-        comments within choices, and those shouldn't be considered as choice
-        items either. Only drivers/usb/gadget/Kconfig seems to depend on any of
-        this. This method computes the "actual" items in the choice and sets
-        the is_choice_symbol_ flag on them (retrieved via is_choice_symbol()).
+        choice, it is no longer viewed as a choice item. (This is quite
+        possibly a bug, but some things consciously use it... ugh. It stems
+        from automatic submenu creation.) In addition, it's possible to have
+        choices and comments within choices, and those shouldn't be considered
+        choice items either. Only drivers/usb/gadget/Kconfig seems to depend on
+        any of this. This method computes the "actual" items in the choice and
+        sets the is_choice_symbol_ flag on them (retrieved via
+        is_choice_symbol()).
 
         Don't let this scare you: an earlier version simply checked for a
         sequence of symbols where all symbols after the first appeared in the
@@ -3407,18 +2950,16 @@ class Choice(Item, _HasVisibility):
         drivers/usb/gadget/Kconfig turns even more sinister. It might very well
         be overkilling things (especially if that file is refactored ;)."""
 
-        items = self.block.get_items()
-
         # Items might depend on each other in a tree structure, so we need a
         # stack to keep track of the current tentative parent
         stack = []
 
-        for item in items:
+        for item in self.block:
             if not isinstance(item, Symbol):
                 stack = []
                 continue
 
-            while stack != []:
+            while stack:
                 if item._has_auto_menu_dep_on(stack[-1]):
                     # The item should not be viewed as a choice item, so don't
                     # set item.is_choice_symbol_.
@@ -3443,8 +2984,8 @@ class Choice(Item, _HasVisibility):
         return selection
 
     def _invalidate(self):
-        _HasVisibility._invalidate(self)
         self.cached_selection = None
+        self.cached_visibility = None
 
     def _unset_user_value(self):
         self._invalidate()
@@ -3452,7 +2993,7 @@ class Choice(Item, _HasVisibility):
         self.user_mode = None
 
     def _make_conf(self):
-        return self.block._make_conf()
+        return _make_block_conf(self.block)
 
 class Comment(Item):
 
@@ -3482,9 +3023,10 @@ class Comment(Item):
         representation."""
         return self.parent
 
-    def get_referenced_symbols(self, refs_from_enclosing = False):
+    def get_referenced_symbols(self, refs_from_enclosing=False):
         """See Symbol.get_referenced_symbols()."""
-        return self.all_referenced_syms if refs_from_enclosing else self.referenced_syms
+        return self.all_referenced_syms if refs_from_enclosing else \
+               self.referenced_syms
 
     def get_location(self):
         """Returns the location of the comment as a (filename, linenr) tuple,
@@ -3492,18 +3034,21 @@ class Comment(Item):
         return (self.filename, self.linenr)
 
     def __str__(self):
-        """Returns a string containing various information about the comment."""
+        """Returns a string containing various information about the
+        comment."""
         dep_str = self.config._expr_val_str(self.orig_deps, "(no dependencies)")
 
-        additional_deps_str = " " + self.config._expr_val_str(self.deps_from_containing,
-                                                              "(no additional dependencies)")
+        additional_deps_str = " " + \
+          self.config._expr_val_str(self.deps_from_containing,
+                                    "(no additional dependencies)")
 
-        return _sep_lines("Comment",
-                          "Text: "         + str(self.text),
-                          "Dependencies: " + dep_str,
-                          "Additional dependencies from enclosing menus and if's:",
-                          additional_deps_str,
-                          "Location: {0}:{1}".format(self.filename, self.linenr))
+        return _lines("Comment",
+                      "Text: "         + str(self.text),
+                      "Dependencies: " + dep_str,
+                      "Additional dependencies from enclosing menus and "
+                        "ifs:",
+                      additional_deps_str,
+                      "Location: {0}:{1}".format(self.filename, self.linenr))
 
     #
     # Private methods
@@ -3520,31 +3065,68 @@ class Comment(Item):
         self.dep_expr = None
 
         # Dependency expression without dependencies from enclosing menus and
-        # if's propagated
+        # ifs propagated
         self.orig_deps = None
 
-        # Dependencies inherited from containing menus and if's
-        self.deps_from_containing = None
+        # Dependencies inherited from containing menus and ifs
+        self.deps_from_containing = None
+
+        # The set of symbols referenced by this comment (see
+        # get_referenced_symbols())
+        self.referenced_syms = set()
+
+        # Like 'referenced_syms', but includes symbols from
+        # dependencies inherited from enclosing menus and ifs
+        self.all_referenced_syms = None
+
+        self.filename = None
+        self.linenr = None
+
+    def _make_conf(self):
+        if self.config._eval_expr(self.dep_expr) != "n":
+            return ["\n#\n# {0}\n#".format(self.text)]
+        return []
+
+class Kconfig_Syntax_Error(Exception):
+    """Exception raised for syntax errors."""
+    pass
+
+class Internal_Error(Exception):
+    """Exception raised for internal errors."""
+    pass
+
+#
+# Public functions
+#
 
-        # The set of symbols referenced by this comment (see
-        # get_referenced_symbols())
-        self.referenced_syms = set()
+def tri_less(v1, v2):
+    """Returns True if the tristate v1 is less than the tristate v2, where "n",
+    "m" and "y" are ordered from lowest to highest."""
+    return tri_to_int[v1] < tri_to_int[v2]
 
-        # Like 'referenced_syms', but includes symbols from
-        # dependencies inherited from enclosing menus and if's
-        self.all_referenced_syms = None
+def tri_less_eq(v1, v2):
+    """Returns True if the tristate v1 is less than or equal to the tristate
+    v2, where "n", "m" and "y" are ordered from lowest to highest."""
+    return tri_to_int[v1] <= tri_to_int[v2]
 
-        self.filename = None
-        self.linenr = None
+def tri_greater(v1, v2):
+    """Returns True if the tristate v1 is greater than the tristate v2, where
+    "n", "m" and "y" are ordered from lowest to highest."""
+    return tri_to_int[v1] > tri_to_int[v2]
 
-    def _make_conf(self):
-        if self.config._eval_expr(self.dep_expr) != "n":
-            return ["\n#\n# {0}\n#".format(self.text)]
-        return []
+def tri_greater_eq(v1, v2):
+    """Returns True if the tristate v1 is greater than or equal to the tristate
+    v2, where "n", "m" and "y" are ordered from lowest to highest."""
+    return tri_to_int[v1] >= tri_to_int[v2]
+
+#
+# Internal classes
+#
 
-class _Feed:
+class _Feed(object):
 
-    """Class for working with sequences in a stream-like fashion; handy for tokens."""
+    """Class for working with sequences in a stream-like fashion; handy for
+    tokens."""
 
     def __init__(self, items):
         self.items = items
@@ -3562,47 +3144,40 @@ class _Feed:
     def peek_next(self):
         return None if self.i >= self.length else self.items[self.i]
 
-    def go_to_start(self):
-        self.i = 0
-
-    def __getitem__(self, index):
-        return self.items[index]
-
-    def __len__(self):
-        return len(self.items)
-
-    def is_empty(self):
-        return self.items == []
-
     def check(self, token):
         """Check if the next token is 'token'. If so, remove it from the token
         feed and return True. Otherwise, leave it in and return False."""
-        if self.i >= self.length:
-            return None
-
-        if self.items[self.i] == token:
+        if self.i < self.length and self.items[self.i] == token:
             self.i += 1
             return True
-
         return False
 
-    def remove_while(self, pred):
-        while self.i < self.length and pred(self.items[self.i]):
-            self.i += 1
-
     def go_back(self):
         if self.i <= 0:
-            _internal_error("Attempt to move back in Feed while already at the beginning.")
+            _internal_error("Attempt to move back in Feed while already at "
+                            "the beginning.")
         self.i -= 1
 
+    def go_to_start(self):
+        self.i = 0
+
+    def __len__(self):
+        return self.length
+
 class _FileFeed(_Feed):
 
-    """Feed subclass that keeps track of the current filename and line
+    """_Feed subclass that feeds lines from a file. Joins any line ending in
+    \\ with the following line. Keeps track of the filename and current line
     number."""
 
-    def __init__(self, lines, filename):
+    def __init__(self, filename):
         self.filename = _clean_up_path(filename)
-        _Feed.__init__(self, lines)
+        _Feed.__init__(self, _get_lines(filename))
+
+    def remove_blank(self):
+        """Removes lines until the first non-blank (not all-space) line."""
+        while self.i < self.length and self.items[self.i].isspace():
+            self.i += 1
 
     def get_filename(self):
         return self.filename
@@ -3611,66 +3186,199 @@ class _FileFeed(_Feed):
         return self.i
 
 #
-# Misc. public global utility functions
+# Internal functions
 #
 
-def tri_less(v1, v2):
-    """Returns True if the tristate v1 is less than the tristate v2, where "n",
-    "m" and "y" are ordered from lowest to highest. Otherwise, returns
-    False."""
-    return tri_to_int[v1] < tri_to_int[v2]
+def _get_visibility(sc):
+    """Symbols and Choices have a "visibility" that acts as an upper bound on
+    the values a user can set for them, corresponding to the visibility in e.g.
+    'make menuconfig'. This function calculates the visibility for the Symbol
+    or Choice 'sc' -- the logic is nearly identical."""
+    if sc.cached_visibility is None:
+        vis = "n"
+        for _, cond_expr in sc.prompts:
+            vis = sc.config._eval_max(vis, cond_expr)
 
-def tri_less_eq(v1, v2):
-    """Returns True if the tristate v1 is less than or equal to the tristate
-    v2, where "n", "m" and "y" are ordered from lowest to highest. Otherwise,
-    returns False."""
-    return tri_to_int[v1] <= tri_to_int[v2]
+        if isinstance(sc, Symbol) and sc.is_choice_symbol_:
+            vis = sc.config._eval_min(vis, _get_visibility(sc.parent))
 
-def tri_greater(v1, v2):
-    """Returns True if the tristate v1 is greater than the tristate v2, where
-    "n", "m" and "y" are ordered from lowest to highest. Otherwise, returns
-    False."""
-    return tri_to_int[v1] > tri_to_int[v2]
+        # Promote "m" to "y" if we're dealing with a non-tristate
+        if vis == "m" and sc.type != TRISTATE:
+            vis = "y"
 
-def tri_greater_eq(v1, v2):
-    """Returns True if the tristate v1 is greater than or equal to the tristate
-    v2, where "n", "m" and "y" are ordered from lowest to highest. Otherwise,
-    returns False."""
-    return tri_to_int[v1] >= tri_to_int[v2]
+        sc.cached_visibility = vis
 
-#
-# Helper functions, mostly related to text processing
-#
+    return sc.cached_visibility
 
-def _strip_quotes(s, line, filename, linenr):
-    """Removes any quotes surrounding 's' if it has them; otherwise returns 's'
-    unmodified."""
-    s = s.strip()
-    if not s:
+def _make_and(e1, e2):
+    """Constructs an AND (&&) expression. Performs trivial simplification.
+    Nones equate to 'y'.
+
+    Note: returns None if e1 == e2 == None."""
+    if e1 is None or e1 == "y":
+        return e2
+    if e2 is None or e2 == "y":
+        return e1
+    if e1 == "n" or e2 == "n":
+        return "n"
+
+    # Prefer to merge/update argument list if possible instead of creating
+    # a new AND node
+
+    if isinstance(e1, tuple) and e1[0] == AND:
+        if isinstance(e2, tuple) and e2[0] == AND:
+            return (AND, e1[1] + e2[1])
+        return (AND, e1[1] + [e2])
+
+    if isinstance(e2, tuple) and e2[0] == AND:
+        return (AND, e2[1] + [e1])
+
+    return (AND, [e1, e2])
+
+def _make_or(e1, e2):
+    """Constructs an OR (||) expression. Performs trivial simplification and
+    avoids Nones. Nones equate to 'y', which is usually what we want, but needs
+    to be kept in mind."""
+
+    # Perform trivial simplification and avoid None's (which
+    # correspond to y's)
+    if e1 is None or e2 is None or e1 == "y" or e2 == "y":
+        return "y"
+    if e1 == "n":
+        return e2
+    if e2 == "n":
+        return e1
+
+    # Prefer to merge/update argument list if possible instead of creating
+    # a new OR node
+
+    if isinstance(e1, tuple) and e1[0] == OR:
+        if isinstance(e2, tuple) and e2[0] == OR:
+            return (OR, e1[1] + e2[1])
+        return (OR, e1[1] + [e2])
+
+    if isinstance(e2, tuple) and e2[0] == OR:
+        return (OR, e2[1] + [e1])
+
+    return (OR, [e1, e2])
+
+def _get_expr_syms(expr):
+    """Returns the set() of symbols appearing in expr."""
+    res = set()
+    if expr is None:
+        return res
+
+    def rec(expr):
+        if isinstance(expr, Symbol):
+            res.add(expr)
+            return
+        if isinstance(expr, str):
+            return
+
+        e0 = expr[0]
+        if e0 == AND or e0 == OR:
+            for term in expr[1]:
+                rec(term)
+        elif e0 == NOT:
+            rec(expr[1])
+        elif e0 == EQUAL or e0 == UNEQUAL:
+            _, v1, v2 = expr
+            if isinstance(v1, Symbol):
+                res.add(v1)
+            if isinstance(v2, Symbol):
+                res.add(v2)
+        else:
+            _internal_error("Internal error while fetching symbols from an "
+                            "expression with token stream {0}.".format(expr))
+
+    rec(expr)
+    return res
+
+def _str_val(obj):
+    """Returns the value of obj as a string. If obj is not a string (constant
+    symbol), it must be a Symbol."""
+    return obj if isinstance(obj, str) else obj.get_value()
+
+def _make_block_conf(block):
+    """Returns a list of .config strings for a block (list) of items."""
+
+    # Collect the substrings in a list and later use join() instead of += to
+    # build the final .config contents. With older Python versions, this yields
+    # linear instead of quadratic complexity.
+    strings = []
+    for item in block:
+        strings.extend(item._make_conf())
+    return strings
+
+def _sym_str_string(sym_or_str):
+    if isinstance(sym_or_str, str):
+        return '"' + sym_or_str + '"'
+    return sym_or_str.name
+
+def _intersperse(lst, op):
+    """_expr_to_str() helper. Gets the string representation of each expression
+    in lst and produces a list where op has been inserted between the
+    elements."""
+    if not lst:
         return ""
-    if s[0] == '"' or s[0] == "'":
-        if len(s) < 2 or s[-1] != s[0]:
-            _parse_error(line,
-                         "malformed string literal",
-                         filename,
-                         linenr)
-        return s[1:-1]
-    return s
+
+    res = []
+
+    def handle_sub_expr(expr):
+        no_parens = isinstance(expr, (str, Symbol)) or \
+                    expr[0] in (EQUAL, UNEQUAL) or \
+                    precedence[op] <= precedence[expr[0]]
+        if not no_parens:
+            res.append("(")
+        res.extend(_expr_to_str_rec(expr))
+        if not no_parens:
+            res.append(")")
+
+    op_str = op_to_str[op]
+
+    handle_sub_expr(lst[0])
+    for expr in lst[1:]:
+        res.append(op_str)
+        handle_sub_expr(expr)
+
+    return res
+
+def _expr_to_str_rec(expr):
+    if expr is None:
+        return [""]
+
+    if isinstance(expr, (Symbol, str)):
+        return [_sym_str_string(expr)]
+
+    e0 = expr[0]
+
+    if e0 == AND or e0 == OR:
+        return _intersperse(expr[1], expr[0])
+
+    if e0 == NOT:
+        need_parens = not isinstance(expr[1], (str, Symbol))
+
+        res = ["!"]
+        if need_parens:
+            res.append("(")
+        res.extend(_expr_to_str_rec(expr[1]))
+        if need_parens:
+            res.append(")")
+        return res
+
+    if e0 == EQUAL or e0 == UNEQUAL:
+        return [_sym_str_string(expr[1]),
+                op_to_str[expr[0]],
+                _sym_str_string(expr[2])]
+
+def _expr_to_str(expr):
+    return "".join(_expr_to_str_rec(expr))
 
 def _indentation(line):
-    """Returns the indentation of the line, treating tab stops as being spaced
-    8 characters apart."""
-    if line.isspace():
-        _internal_error("Attempt to take indentation of blank line.")
-    indent = 0
-    for c in line:
-        if c == " ":
-            indent += 1
-        elif c == "\t":
-            # Go to the next tab stop
-            indent = (indent + 8) & ~7
-        else:
-            return indent
+    """Returns the length of the line's leading whitespace, treating tab stops
+    as being spaced 8 characters apart."""
+    line = line.expandtabs()
+    return len(line) - len(line.lstrip())
 
 def _deindent(line, indent):
     """Deindent 'line' by 'indent' spaces."""
@@ -3686,8 +3394,8 @@ def _is_base_n(s, n):
     except ValueError:
         return False
 
-def _sep_lines(*args):
-    """Returns a string comprised of all arguments, with newlines inserted
+def _lines(*args):
+    """Returns a string consisting of all arguments, with newlines inserted
     between them."""
     return "\n".join(args)
 
@@ -3706,94 +3414,146 @@ def _get_lines(filename):
     with open(filename, "r") as f:
         lines = []
         accum = ""
-        while 1:
-            line = f.readline()
-
-            if line == "":
-                return lines
-
+        for line in f:
             if line.endswith("\\\n"):
                 accum += line[:-2]
             else:
-                accum += line
-                lines.append(accum)
+                lines.append(accum + line)
                 accum = ""
-
-def _strip_trailing_slash(path):
-    """Removes any trailing slash from 'path'."""
-    return path[:-1] if path.endswith("/") else path
+        return lines
 
 def _clean_up_path(path):
-    """Strips any initial "./" and trailing slash from 'path'."""
+    """Strips an initial "./" and any trailing slashes from 'path'."""
     if path.startswith("./"):
         path = path[2:]
-    return _strip_trailing_slash(path)
+    return path.rstrip("/")
+
+def _stderr_msg(msg, filename, linenr):
+    if filename is not None:
+        sys.stderr.write("{0}:{1}: ".format(_clean_up_path(filename), linenr))
+    sys.stderr.write(msg + "\n")
+
+def _tokenization_error(s, filename, linenr):
+    loc = "" if filename is None else "{0}:{1}: ".format(filename, linenr)
+    raise Kconfig_Syntax_Error("{0}Couldn't tokenize '{1}'"
+                               .format(loc, s.strip()))
+
+def _parse_error(s, msg, filename, linenr):
+    loc = "" if filename is None else "{0}:{1}: ".format(filename, linenr)
+    raise Kconfig_Syntax_Error("{0}Couldn't parse '{1}'{2}"
+                               .format(loc, s.strip(),
+                                       "." if msg is None else ": " + msg))
+
+def _internal_error(msg):
+    raise Internal_Error(msg +
+      "\nSorry! You may want to send an email to ulfalizer a.t Google's "
+      "email service to tell me about this. Include the message above and the "
+      "stack trace and describe what you were doing.")
 
 #
-# Error handling
+# Internal global constants
 #
 
-class Kconfig_Syntax_Error(Exception):
-    """Exception raised for syntax errors."""
-    pass
+# Tokens
+(T_AND, T_OR, T_NOT,
+ T_OPEN_PAREN, T_CLOSE_PAREN,
+ T_EQUAL, T_UNEQUAL,
+ T_MAINMENU, T_MENU, T_ENDMENU,
+ T_SOURCE, T_CHOICE, T_ENDCHOICE,
+ T_COMMENT, T_CONFIG, T_MENUCONFIG,
+ T_HELP, T_IF, T_ENDIF, T_DEPENDS, T_ON,
+ T_OPTIONAL, T_PROMPT, T_DEFAULT,
+ T_BOOL, T_TRISTATE, T_HEX, T_INT, T_STRING,
+ T_DEF_BOOL, T_DEF_TRISTATE,
+ T_SELECT, T_RANGE, T_OPTION, T_ALLNOCONFIG_Y, T_ENV,
+ T_DEFCONFIG_LIST, T_MODULES, T_VISIBLE) = range(39)
+
+# The leading underscore before the function assignments below prevent pydoc
+# from listing them. The constants could be hidden too, but they're fairly
+# obviously internal anyway, so don't bother spamming the code.
+
+# Keyword to token map. Note that the get() method is assigned directly as a
+# small optimization.
+_get_keyword = { "mainmenu"       : T_MAINMENU,
+                 "menu"           : T_MENU,
+                 "endmenu"        : T_ENDMENU,
+                 "endif"          : T_ENDIF,
+                 "endchoice"      : T_ENDCHOICE,
+                 "source"         : T_SOURCE,
+                 "choice"         : T_CHOICE,
+                 "config"         : T_CONFIG,
+                 "comment"        : T_COMMENT,
+                 "menuconfig"     : T_MENUCONFIG,
+                 "help"           : T_HELP,
+                 "if"             : T_IF,
+                 "depends"        : T_DEPENDS,
+                 "on"             : T_ON,
+                 "optional"       : T_OPTIONAL,
+                 "prompt"         : T_PROMPT,
+                 "default"        : T_DEFAULT,
+                 "bool"           : T_BOOL,
+                 "boolean"        : T_BOOL,
+                 "tristate"       : T_TRISTATE,
+                 "int"            : T_INT,
+                 "hex"            : T_HEX,
+                 "def_bool"       : T_DEF_BOOL,
+                 "def_tristate"   : T_DEF_TRISTATE,
+                 "string"         : T_STRING,
+                 "select"         : T_SELECT,
+                 "range"          : T_RANGE,
+                 "option"         : T_OPTION,
+                 "allnoconfig_y"  : T_ALLNOCONFIG_Y,
+                 "env"            : T_ENV,
+                 "defconfig_list" : T_DEFCONFIG_LIST,
+                 "modules"        : T_MODULES,
+                 "visible"        : T_VISIBLE }.get
 
-class Internal_Error(Exception):
-    """Exception raised for internal errors."""
-    pass
+# Strings to use for True and False
+bool_str = { False : "false", True : "true" }
 
-def _tokenization_error(s, index, filename, linenr):
-    if filename is not None:
-        assert linenr is not None
-        sys.stderr.write("{0}:{1}:\n".format(filename, linenr))
+# Tokens after which identifier-like lexemes are treated as strings. T_CHOICE
+# is included to avoid symbols being registered for named choices.
+string_lex = frozenset((T_BOOL, T_TRISTATE, T_INT, T_HEX, T_STRING, T_CHOICE,
+                        T_PROMPT, T_MENU, T_COMMENT, T_SOURCE, T_MAINMENU))
 
-    if s.endswith("\n"):
-        s = s[:-1]
-
-    # Calculate the visual offset corresponding to index 'index' in 's'
-    # assuming tabstops are spaced 8 characters apart
-    vis_index = 0
-    for c in s[:index]:
-        if c == "\t":
-            vis_index = (vis_index + 8) & ~7
-        else:
-            vis_index += 1
+# Matches the initial token on a line; see _tokenize().
+_initial_token_re_match = re.compile(r"[^\w]*(\w+)").match
 
-    # Don't output actual tabs to be independent of how the terminal renders
-    # them
-    s = s.expandtabs()
+# Matches an identifier/keyword optionally preceded by whitespace
+_id_keyword_re_match = re.compile(r"\s*([\w./-]+)").match
 
-    raise Kconfig_Syntax_Error, (
-        _sep_lines("Error during tokenization at location indicated by caret.\n",
-                   s,
-                   " " * vis_index + "^\n"))
+# Regular expressions for parsing .config files
+_set_re_match   = re.compile(r"CONFIG_(\w+)=(.*)").match
+_unset_re_match = re.compile(r"# CONFIG_(\w+) is not set").match
 
-def _parse_error(s, msg, filename, linenr):
-    error_str = ""
+# Regular expression for finding $-references to symbols in strings
+_sym_ref_re_search = re.compile(r"\$[A-Za-z0-9_]+").search
 
-    if filename is not None:
-        assert linenr is not None
-        error_str += "{0}:{1}: ".format(filename, linenr)
+# Integers representing symbol types
+UNKNOWN, BOOL, TRISTATE, STRING, HEX, INT = range(6)
 
-    if s.endswith("\n"):
-        s = s[:-1]
+# Strings to use for types
+typename = { UNKNOWN : "unknown", BOOL : "bool", TRISTATE : "tristate",
+             STRING : "string", HEX : "hex", INT : "int" }
 
-    error_str += 'Error while parsing "{0}"'.format(s) + \
-      ("." if msg is None else ": " + msg)
+# Token to type mapping
+token_to_type = { T_BOOL : BOOL, T_TRISTATE : TRISTATE, T_STRING : STRING,
+                  T_INT : INT, T_HEX : HEX }
 
-    raise Kconfig_Syntax_Error, error_str
+# Default values for symbols of different types (the value the symbol gets if
+# it is not assigned a user value and none of its 'default' clauses kick in)
+default_value = { BOOL : "n", TRISTATE : "n", STRING : "", INT : "", HEX : "" }
 
-def _internal_error(msg):
-    msg += "\nSorry! You may want to send an email to kconfiglib at gmail.com " \
-           "to tell me about this. Include the message above and the stack " \
-           "trace and describe what you were doing."
+# Indicates that no item is selected in a choice statement
+NO_SELECTION = 0
 
-    raise Internal_Error, msg
+# Integers representing expression types
+AND, OR, NOT, EQUAL, UNEQUAL = range(5)
 
-if use_psyco:
-    import psyco
+# Map from tristate values to integers
+tri_to_int = { "n" : 0, "m" : 1, "y" : 2 }
 
-    Config._tokenize  = psyco.proxy(Config._tokenize)
-    Config._eval_expr = psyco.proxy(Config._eval_expr)
+# Printing-related stuff
 
-    _indentation = psyco.proxy(_indentation)
-    _get_lines   = psyco.proxy(_get_lines)
+op_to_str = { AND : " && ", OR : " || ", EQUAL : " = ", UNEQUAL : " != " }
+precedence = { OR : 0, AND : 1, NOT : 2 }
-- 
2.1.4



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