[PATCH] log: Allow LOG_DEBUG to always enable log output

[Heinrich Schuchardt]

Am 5. August 2020 21:03:28 MESZ schrieb Tom Rini <trini at konsulko.com>:
>On Wed, Aug 05, 2020 at 12:56:17PM -0600, Simon Glass wrote:
>> Hi Tom,
>> 
>> On Wed, 5 Aug 2020 at 12:37, Tom Rini <trini at konsulko.com> wrote:
>> >
>> > On Wed, Aug 05, 2020 at 08:31:55PM +0200, Heinrich Schuchardt
>wrote:
>> > > On 05.08.20 14:56, Tom Rini wrote:
>> > > > On Wed, Aug 05, 2020 at 02:54:05PM +0200, Heinrich Schuchardt
>wrote:
>> > > >> On 05.08.20 14:18, Tom Rini wrote:
>> > > >>> On Sun, Jul 26, 2020 at 08:27:35PM -0600, Simon Glass wrote:
>> > > >>>
>> > > >>>> At present if CONFIG_LOG enabled, putting LOG_DEBUG at the
>top of a file
>> > > >>>> (before log.h inclusion) causes _log() to be executed for
>every log()
>> > > >>>> call, regardless of the build- or run-time logging level.
>> > > >>>>
>> > > >>>> However there is no guarantee that the log record will
>actually be
>> > > >>>> displayed. If the current log level is lower than LOGL_DEBUG
>then it will
>> > > >>>> not be.
>> > > >>>>
>> > > >>>> Add a way to signal that the log record should always be
>displayed and
>> > > >>>> update log_passes_filters() to handle this.
>> > > >>>>
>> > > >>>> Signed-off-by: Simon Glass <sjg at chromium.org>
>> > > >>>
>> > > >>> This exposes an underlying problem with LOG and clang I
>believe:
>> > > >>> https://gitlab.denx.de/u-boot/u-boot/-/jobs/135789
>> > > >>>
>> > > >>
>> > > >> include/log.h:147:44: note: expanded from macro 'log'
>> > > >>         if (CONFIG_IS_ENABLED(LOG) && (_LOG_DEBUG || _l <=
>> > > >> _LOG_MAX_LEVEL)) \
>> > > >>                                                   ^
>> > > >> drivers/misc/p2sb_emul.c:197:10: error: converting the enum
>constant to
>> > > >> a boolean [-Werror,-Wint-in-bool-context]
>> > > >>
>> > > >> This seems to be a Clang bug. _LOG_DEBUG is not an enum:
>> > > >>
>> > > >> #if CONFIG_IS_ENABLED(LOG)
>> > > >> #ifdef LOG_DEBUG
>> > > >> #define _LOG_DEBUG      1
>> > > >> #else
>> > > >> #define _LOG_DEBUG      0
>> > > >> #endif
>> > > >>
>> > > >> So there seems to be a bug in the Clang you used.
>> > > >>
>> > > >> Compiling with clang on Debian Bullseye does not show the
>problem:
>> > > >>
>> > > >> make HOSTCC=clang sandbox_defconfig
>> > > >> make HOSTCC=clang CC=clang -j8
>> > > >>
>> > > >> clang version 9.0.1-13
>> > > >> LLVM version 9.0.1
>> > > >>
>> > > >> Which Clang version did you use?
>> > > >>
>> > > >> This is the change that added the test:
>> > > >> https://reviews.llvm.org/D63082
>> > > >>
>> > > >> -Wint-in-bool-context seems to be new in Clang 10.
>> > > >>
>> > > >> All over the U-Boot code we assume that a non-zero integer is
>true. Do
>> > > >> we really want to enable -Wint-in-bool-context?
>> > > >
>> > > > I'm using the official Clang 10 stable builds.
>> > > >
>> > >
>> > > Do you really want to forbid using integers as booleans
>> > > (-Wint-in-bool-context)?
>> >
>> > So, interesting.  The Linux kernel isn't disabling this warning. 
>It's
>> > mentioned in two commits, one of which is "clang found a bug here",
>of
>> > which this is not the case.  The other is more like ours:
>> > commit 968e5170939662341242812b9c82ef51cf140a33
>> > Author: Nathan Chancellor <natechancellor at gmail.com>
>> > Date:   Thu Sep 26 09:22:59 2019 -0700
>> >
>> >     tracing: Fix clang -Wint-in-bool-context warnings in IF_ASSIGN
>macro
>> >
>> >     After r372664 in clang, the IF_ASSIGN macro causes a couple
>hundred
>> >     warnings along the lines of:
>> >
>> >     kernel/trace/trace_output.c:1331:2: warning: converting the
>enum
>> >     constant to a boolean [-Wint-in-bool-context]
>> >     kernel/trace/trace.h:409:3: note: expanded from macro
>> >     'trace_assign_type'
>> >                     IF_ASSIGN(var, ent, struct
>ftrace_graph_ret_entry,
>> >                     ^
>> >     kernel/trace/trace.h:371:14: note: expanded from macro
>'IF_ASSIGN'
>> >                     WARN_ON(id && (entry)->type != id);     \
>> >                                ^
>> >     264 warnings generated.
>> >
>> >     This warning can catch issues with constructs like:
>> >
>> >         if (state == A || B)
>> >
>> >     where the developer really meant:
>> >
>> >         if (state == A || state == B)
>> >
>> >     This is currently the only occurrence of the warning in the
>kernel
>> >     tree across defconfig, allyesconfig, allmodconfig for arm32,
>arm64,
>> >     and x86_64. Add the implicit '!= 0' to the WARN_ON statement to
>fix
>> >     the warnings and find potential issues in the future.
>> >
>> >     Link:
>https://github.com/llvm/llvm-project/commit/28b38c277a2941e9e891b2db30652cfd962f070b
>> >     Link: https://github.com/ClangBuiltLinux/linux/issues/686
>> >     Link:
>http://lkml.kernel.org/r/20190926162258.466321-1-natechancellor@gmail.com
>> >
>> >     Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>
>> >     Signed-off-by: Nathan Chancellor <natechancellor at gmail.com>
>> >     Signed-off-by: Steven Rostedt (VMware) <rostedt at goodmis.org>
>> >
>> > Which is like our case, and reworking the test to be explicit.  I
>lean
>> > towards that.
>> 
>> Oh dear I really want to vote against that.
>> 
>> if (x)
>> 
>> should allow C to consider x to be a boolean. I am hitting this in
>> Zephyr and feels like it is undoing a long-standing C feature, with
>> major disruption, for no benefit I can detect.
>> 
>> Hopefully I am misunderstanding what -Wint-in-bool-context means, and
>> it just applies to enums?
>
>Yes, it's not the simple case, it's the complex case as noted in the
>kernel commit message.  Our change I believe would be:
>
>diff --git a/include/log.h b/include/log.h
>index 2859ce1f2e72..91ca2e0523f7 100644
>--- a/include/log.h
>+++ b/include/log.h
>@@ -141,7 +141,7 @@ static inline int _log_nop(enum log_category_t cat,
>enum log_level_t level,
> /* Emit a log record if the level is less that the maximum */
> #define log(_cat, _level, _fmt, _args...) ({ \
> 	int _l = _level; \
>-	if (CONFIG_IS_ENABLED(LOG) && (_l <= _LOG_MAX_LEVEL || _LOG_DEBUG)) \
>+	if (CONFIG_IS_ENABLED(LOG) && (_l <= _LOG_MAX_LEVEL || _LOG_DEBUG ==
>1)) \

Why wouldn't we define _LOG_DEBUG as true or false? Shouldn't clang know that true is boolean?


> 		_log((enum log_category_t)(_cat), _l, __FILE__, __LINE__, \
> 		      __func__, \
> 		      pr_fmt(_fmt), ##_args); \
>
>It's not a new warning from clang (We've been on LLVM-10 since
>February), it's only that the logging code is now being run through it
>via CI.