From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 380473858D28; Mon, 9 Oct 2023 11:37:59 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 380473858D28 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1696851479; bh=Ncfb5klO95L7F0FxUw7l0Ly7rW1eWCPSOak7MmuAS24=; h=From:To:Subject:Date:From; b=DTHUZFzQJql/Go1VYfcosovl8b4iYQwOcgg0Iw0aeXDQ/y/wex7Lv85X2KMEMRLyN 7rjPbD2HRp4WDyaLQTGrDTZGj+0S7TFOk81YTF209wq6M+6h1h7GGIjTqoLwWleNhJ LwrmyfhI7JuDAs1v8iCK15FscHJC8ccX7XloYPm0= From: "gprocida at google dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug debug/111735] New: incorrect BTF representation of forward-declared enums Date: Mon, 09 Oct 2023 11:37:58 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: debug X-Bugzilla-Version: 13.2.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: gprocida at google 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 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=3D111735 Bug ID: 111735 Summary: incorrect BTF representation of forward-declared enums 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: --- The BTF_FWD_KIND node can only distinguish between struct and union types. (Non-standard) forward-declared enum types need to be represented in some different fashion. I queried this on LKML in July 2020 and was told that then current way to represent such types is as BTF_KIND_ENUM with vlen =3D 0. This is in fact w= hat both Clang and pahole -J do. I think Clang produces slightly better output = than pahole (leaving size as 0).=20 test input: $ cat /tmp/xx.c enum Foo; enum Foo* foo; compilation command: $ gcc -gbtf -c /tmp/xx.c -o /tmp/xx.o unexpected output: $ bpftool btf dump file /tmp/xx.o format raw=20 [1] FWD 'Foo' fwd_kind=3Dstruct [2] PTR '(anon)' type_id=3D1 [3] VAR 'foo' type_id=3D2, linkage=3Dglobal [4] DATASEC '.bss' size=3D0 vlen=3D1 type_id=3D3 offset=3D0 size=3D8 (VAR 'foo') possible expected output (size=3D0): $ clang-15 -target bpf -g -c /tmp/xx.c -o /tmp/xx.o $ pahole -J /tmp/xx.o $ bpftool btf dump file /tmp/xx.o format raw | grep Foo [2] ENUM 'Foo' encoding=3DUNSIGNED size=3D0 vlen=3D0 other possible expected output (size=3D4): $ gcc -g -c /tmp/xx.c -o /tmp/xx.o $ pahole -J /tmp/xx.o $ bpftool btf dump file /tmp/xx.o format raw | grep Foo [1] ENUM 'Foo' encoding=3DUNSIGNED size=3D4 vlen=3D0 GCC version: 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)=