[U-Boot] [PATCH v6 18/20] Adjust dependency rules to permit per-file flags

[Simon Glass]

The dependency rules are currently done in a shell 'for' loop. This does not
permit Makefile variables to adjust preprocessor flags as is done with normal
compile flags, using the CFLAGS_path/file.o syntax.

This change moves the dependency generation into the Makefile itself, and
permits a CPPFLAGS_path/file.o to adjust preprocessor flags on a file or
directory basis.

The CPPFLAGS_... variable is also folded into CFLAGS during the build.

Signed-off-by: Simon Glass <sjg at chromium.org>
---
Changes in v3:
- Change U-Boot's dependency generation to permit per-file flags

Changes in v4:
- 'Improve' dependency generation to deal with source files containing paths
- Make sure that clobber target removes all dependency files

Changes in v5:
- Fix dependency output to include $(obj) for out-of-tree builds

 .gitignore |    2 +-
 Makefile   |    2 +-
 config.mk  |    7 +++++++
 rules.mk   |   44 +++++++++++++++++++++++++++++++++-----------
 4 files changed, 42 insertions(+), 13 deletions(-)

diff --git a/.gitignore b/.gitignore
index 289ffab..1bea75f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -40,7 +40,7 @@
 # Generated files
 #
 
-*.depend
+*.depend*
 /LOG
 /errlog
 /reloc_off
diff --git a/Makefile b/Makefile
index 4de2103..aa78310 100644
--- a/Makefile
+++ b/Makefile
@@ -953,7 +953,7 @@ clean:
 		| xargs rm -f
 
 clobber:	clean
-	@find $(OBJTREE) -type f \( -name '*.depend' \
+	@find $(OBJTREE) -type f \( -name '*.depend*' \
 		-o -name '*.srec' -o -name '*.bin' -o -name u-boot.img \) \
 		-print0 \
 		| xargs -0 rm -f
diff --git a/config.mk b/config.mk
index e2b440d..3fa9eef 100644
--- a/config.mk
+++ b/config.mk
@@ -277,6 +277,13 @@ export	CONFIG_SYS_TEXT_BASE PLATFORM_CPPFLAGS PLATFORM_RELFLAGS CPPFLAGS CFLAGS
 BCURDIR = $(subst $(SRCTREE)/,,$(CURDIR:$(obj)%=%))
 ALL_AFLAGS = $(AFLAGS) $(AFLAGS_$(BCURDIR)/$(@F)) $(AFLAGS_$(BCURDIR))
 ALL_CFLAGS = $(CFLAGS) $(CFLAGS_$(BCURDIR)/$(@F)) $(CFLAGS_$(BCURDIR))
+EXTRA_CPPFLAGS = $(CPPFLAGS_$(BCURDIR)/$(@F)) $(CPPFLAGS_$(BCURDIR))
+ALL_CFLAGS += $(EXTRA_CPPFLAGS)
+
+# The _DEP version uses the $< file target (for dependency generation)
+# See rules.mk
+EXTRA_CPPFLAGS_DEP = $(CPPFLAGS_$(BCURDIR)/$(addsuffix .o,$(basename $<))) \
+		$(CPPFLAGS_$(BCURDIR))
 $(obj)%.s:	%.S
 	$(CPP) $(ALL_AFLAGS) -o $@ $<
 $(obj)%.o:	%.S
diff --git a/rules.mk b/rules.mk
index d79fcd3..22562f3 100644
--- a/rules.mk
+++ b/rules.mk
@@ -25,17 +25,39 @@
 
 _depend:	$(obj).depend
 
-$(obj).depend:	$(src)Makefile $(TOPDIR)/config.mk $(SRCS) $(HOSTSRCS)
-		@rm -f $@
-		@touch $@
-		@for f in $(SRCS); do \
-			g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-			$(CC) -M $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
-		done
-		@for f in $(HOSTSRCS); do \
-			g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-			$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
-		done
+# Split the source files into two camps: those in the current directory, and
+# those somewhere else. For the first camp we want to support CPPFLAGS_<fname>
+# and for the second we don't / can't.
+PWD_SRCS := $(filter $(notdir $(SRCS)),$(SRCS))
+OTHER_SRCS := $(filter-out $(notdir $(SRCS)),$(SRCS))
+
+# This is a list of dependency files to generate
+DEPS := $(basename $(patsubst %,$(obj).depend.%,$(PWD_SRCS)))
+
+# Join all the dependencies into a single file, in three parts
+#	1 .Concatenate all the generated depend files together
+#	2. Add in the deps from OTHER_SRCS which we couldn't process
+#	3. Add in the HOSTSRCS
+$(obj).depend:	$(src)Makefile $(TOPDIR)/config.mk $(DEPS) $(HOSTSRCS)
+	cat /dev/null $(DEPS) >$@
+	@for f in $(OTHER_SRCS); do \
+		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
+		$(CC) -M $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+	done
+	@for f in $(HOSTSRCS); do \
+		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
+		$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+	done
+
+MAKE_DEPEND = $(CC) -M $(CPPFLAGS) $(EXTRA_CPPFLAGS_DEP) \
+		-MQ $(addsuffix .o,$(obj)$(basename $<)) $< >$@
+
+
+$(obj).depend.%:	%.c
+	$(MAKE_DEPEND)
+
+$(obj).depend.%:	%.S
+	$(MAKE_DEPEND)
 
 $(HOSTOBJS): $(obj)%.o: %.c
 	$(HOSTCC) $(HOSTCFLAGS) $(HOSTCFLAGS_$(@F)) $(HOSTCFLAGS_$(BCURDIR)) -o $@ $< -c
-- 
1.7.3.1