From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 0D3ED38533CC; Mon, 12 Dec 2022 14:53:17 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 0D3ED38533CC DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1670856797; bh=nvvghF3wXBBOq7j1XnrI1xBlJ/4Iwbt4IqSsvhhwLWI=; h=From:To:Subject:Date:From; b=HorbfqBuQLkVol6d/AHud9pjfma3urG69PLny/9ZKmXhiuQ78dr0DwydTkKOnccK6 xBU10M3lWq+vNpBDs5xr5+4Ubt3az4rAqtom5ZJwt2qgpe2L+V64YhV3Cwwu7eWkEV Jnd1lj+SxJHVqgWZ5DOJvcU9ShaI2rWuVsrnyogc= From: "martid0311 at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c/108076] New: GCC with -O3 produces code which fails to link Date: Mon, 12 Dec 2022 14:53:14 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c X-Bugzilla-Version: 11.3.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: martid0311 at gmail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone attachments.created Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108076 Bug ID: 108076 Summary: GCC with -O3 produces code which fails to link Product: gcc Version: 11.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: martid0311 at gmail dot com Target Milestone: --- Created attachment 54074 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54074&action=3Dedit The source code which fails to compile The attached source file ("compiler-output.c") fails to link with GCC with = -O3 (compiling for x86_64). I've tested it using "gcc (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0", but someone on IRC has confirmed that it's = also an issue on "gcc (Debian 12.2.0-9.1) 12.2.0". Running `gcc -O3 compiler-output.c` fails with this set of errors: /usr/bin/ld: /tmp/ccgWgyyV.o: warning: relocation against `.L8' in read-only section `.text.startup' /usr/bin/ld: /tmp/ccgWgyyV.o: in function `main': gnuc-compiler-output.c:(.text.startup+0x2f): undefined reference to `.L7' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x36): undefined referen= ce to `.L15' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x48): undefined referen= ce to `.L5' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x5a): undefined referen= ce to `.L6' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x6a): undefined referen= ce to `.L8' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x76): undefined referen= ce to `.L9' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x90): undefined referen= ce to `.L10' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0x9b): undefined referen= ce to `.L11' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0xa9): undefined referen= ce to `.L12' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0xb5): undefined referen= ce to `.L13' /usr/bin/ld: gnuc-compiler-output.c:(.text.startup+0xcf): undefined referen= ce to `.L14' /usr/bin/ld: warning: creating DT_TEXTREL in a PIE collect2: error: ld returned 1 exit status I've looked at the generated assembly code (using `gcc -S`), and sure enoug= h, the main function contains code like "leaq .L15(%rip), %rdx" and "leaq= =20=20=20 .L5(%rip), %rax" even though there's no label called .L15 or .L5. The source code contains a label jump table which gets initialized like thi= s: static void *jmp_targets[62]; int main() { jmp_targets[0] =3D &&instr_0; jmp_targets[1] =3D &&instr_1; jmp_targets[2] =3D &&instr_2; jmp_targets[7] =3D &&instr_7; ... If we change the code to use an initializer list it works: int main() { void *jmp_targets[] =3D { [0] =3D &&instr_0, [1] =3D &&instr_1, [2] =3D &&instr_2, [7] =3D &&instr_7, ... Interestingly, it also works if we compile with `-O3 -flto`. Note: the code will segfault unless you provide it command line arguments. = If you want to try to run it, run something like `./a.out 5 10`. It will print= the sum of the two numbers. Output of `gcc -v`: Using built-in specs. COLLECT_GCC=3Dgcc COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/x86_64-linux-gnu/11/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'Ubuntu 11.3.0-1ubuntu1~22.04' --with-bugurl=3Dfile:///usr/share/doc/gcc-11/README.= Bugs --enable-languages=3Dc,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix= =3D/usr --with-gcc-major-version-only --program-suffix=3D-11 --program-prefix=3Dx86_64-linux-gnu- --enable-shared --enable-linker-build-= id --libexecdir=3D/usr/lib --without-included-gettext --enable-threads=3Dposix --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-11-xKiWfi/gcc-11-11.3.0/= debian/tmp-nvptx/usr,amdgcn-amdhsa=3D/build/gcc-11-xKiWfi/gcc-11-11.3.0/deb= ian/tmp-gcn/usr --without-cuda-driver --enable-checking=3Drelease --build=3Dx86_64-linux-gnu --host=3Dx86_64-linux-gnu --target=3Dx86_64-linux-gnu --with-build-config=3Dbootstrap-lto-lean --enable-link-serialization=3D2 Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)=