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From: "gprocida at google dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug debug/112372] New: GCC omits function location in DWARF at
 higher optimisation levels
Date: Fri, 03 Nov 2023 18:36:35 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: debug
X-Bugzilla-Version: 13.2.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: gprocida at google dot com
X-Bugzilla-Status: UNCONFIRMED
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112372

            Bug ID: 112372
           Summary: GCC omits function location in DWARF at higher
                    optimisation levels
           Product: gcc
           Version: 13.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gprocida at google dot com
  Target Milestone: ---

Source:

void x(signed char c) { (void) c; }
void y(char c) { (void) c; }
void z(unsigned char c) { (void) c; } // not needed

GCC versions tested: 11.4.0, 12.3.0, 13.2.0
DWARF versions tested: 3, 4, 5
Optimisation levels tests: 0, 1, g (all good); 2, 3, fast, s (all bad)

At lower levels of optimisation, the 3 functions are described with
straightforward DIEs.

At higher levels of optimisation, they are... a mess.

x has abstract origin
y is missing location (PC)
z looks normal

The missing location means that binary analysis tools, like libabigail, can=
not
associated the symbol y with its type.

FWIW, Clang does not have this issue.

Remove x: issue disappears.
Remove y: issue disappears.
Remove z: issue persists.

gcc -v
Using built-in specs.
COLLECT_GCC=3Dgcc
COLLECT_LTO_WRAPPER=3D/usr/libexec/gcc/x86_64-linux-gnu/13/lto-wrapper
OFFLOAD_TARGET_NAMES=3Dnvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=3D1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion=3D'Debian 13.2.0-4'
--with-bugurl=3Dfile:///usr/share/doc/gcc-13/README.Bugs
--enable-languages=3Dc,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=3D/usr
--with-gcc-major-version-only --program-suffix=3D-13
--program-prefix=3Dx86_64-linux-gnu- --enable-shared --enable-linker-build-=
id
--libexecdir=3D/usr/libexec --without-included-gettext --enable-threads=3Dp=
osix
--libdir=3D/usr/lib --enable-nls --enable-bootstrap --enable-clocale=3Dgnu
--enable-libstdcxx-debug --enable-libstdcxx-time=3Dyes
--with-default-libstdcxx-abi=3Dnew --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-=
zlib
--enable-libphobos-checking=3Drelease --with-target-system-zlib=3Dauto
--enable-objc-gc=3Dauto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=3Di686 --with-abi=3Dm64 --with-multilib-list=3Dm32,m64,mx32
--enable-multilib --with-tune=3Dgeneric
--enable-offload-targets=3Dnvptx-none=3D/build/gcc-13-oyarai/gcc-13-13.2.0/=
debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc-13-oyarai/gcc-13-13.2.0/deb=
ian/tmp-gcn/usr
--enable-offload-defaulted --without-cuda-driver --enable-checking=3Drelease
--build=3Dx86_64-linux-gnu --host=3Dx86_64-linux-gnu --target=3Dx86_64-linu=
x-gnu
--with-build-config=3Dbootstrap-lto-lean --enable-link-serialization=3D28
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.2.0 (Debian 13.2.0-4)=20

gcc -Wall -Wextra -o x.o -O2 -c -g x.c=