[PATCH] log: Allow LOG_DEBUG to always enable log output
Tom Rini
trini at konsulko.com
Wed Aug 5 21:03:28 CEST 2020
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)) \
_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.
--
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 659 bytes
Desc: not available
URL: <https://lists.denx.de/pipermail/u-boot/attachments/20200805/6ae0559f/attachment.sig>
More information about the U-Boot
mailing list