Re: [Buildroot] [PATCH v2] package/valgrind: fix build with a libgcc built without optimization

From: Thomas Petazzoni via buildroot <buildroot@buildroot.org>
To: Yegor Yefremov <yegorslists@googlemail.com>
Cc: buildroot@buildroot.org
Subject: Re: [Buildroot] [PATCH v2] package/valgrind: fix build with a libgcc built without optimization
Date: Thu, 22 Oct 2026 11:32:18 +0200	[thread overview]
Message-ID: <atnYHB0ChkKie60F@windsurf> (raw)
In-Reply-To: <20261022075734.2659243-1-yegorslists@googlemail.com>

On Thu, Oct 22, 2026 at 09:57:34AM +0200, Yegor Yefremov via buildroot wrote:
> The 64 bit division helpers of libgcc (__divdi3 and friends) are
> compiled with -fexceptions -fnon-call-exceptions. Buildroot passes
> TARGET_CFLAGS to gcc through CFLAGS_FOR_TARGET, so with BR2_OPTIMIZE_0
> libgcc itself is built with -O0. GCC then keeps the (empty) exception
> landing pads in those objects, which therefore reference
> _Unwind_Resume() and __gcc_personality_v0(), normally provided by
> libgcc_eh.a. Valgrind links its tools with -nodefaultlibs, so that
> library is not available and the link fails on 32 bit targets:
> 
>   ld: libgcc.a(_divdi3.o): in function `__divdi3':
>   libgcc2.c:1226: undefined reference to `_Unwind_Resume'
>   ld: libgcc.a(_divdi3.o):(.data.rel.local.DW.ref.__gcc_personality_v0[DW.ref.__gcc_personality_v0]+0x0):
>       undefined reference to `__gcc_personality_v0'
>   collect2: error: ld returned 1 exit status
>   make[4]: *** [Makefile:1180: memcheck-x86-linux] Error 1
> 
> Backport the upstream commit providing dummy definitions of both
> symbols in libgcc-sup-<platform>.a, which is linked after -lgcc, so
> toolchains providing the real symbols are unaffected. They can never be
> reached, as Valgrind's core is plain C and never raises an exception.
> 
> This issue has been present since commit 0fe633cdff66 ("gcc: explicitly
> use C{XX}FLAGS_FOR_TARGET instead of --enable-target-optspace"), which
> started building the gcc target libraries with TARGET_CFLAGS, and thus
> with -O0 when BR2_OPTIMIZE_0 is enabled, instead of -Os. This is not a
> gcc regression: both gcc 11 and gcc 15 emit these landing pads at -O0.
> It therefore affects 2015.08 and later, including 2025.02.x and
> 2026.02.x.
> 
> Fixes:
> https://autobuild.buildroot.org/results/4a58c34308095e4d8ae91e0a779c94123ee497f6
> 
> Fixes: 0fe633cdff66febadc50bab3e0af4b3be53811c8 ("gcc: explicitly use C{XX}FLAGS_FOR_TARGET instead of --enable-target-optspace")
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

Applied to master, thanks!

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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