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

Mon Sep 28 06:24:34 CEST 2020

Hi,

On Wed, 5 Aug 2020 at 13:32, Tom Rini <trini at konsulko.com> wrote:
>
> On Wed, Aug 05, 2020 at 09:08:40PM +0200, Heinrich Schuchardt wrote:
> > 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?
>
> Because I didn't think of that instead, mainly.
>

I've resent this patch with just this change to fix clang-10.

Regards,
Simon