[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #13 from H.J. Lu --- (In reply to Andi Kleen from comment #12) > Okay. I only compared gcc-7 (working) vs gcc-9 (broken), but always with LTO. > > Looking at the kernel link it also uses --whole-archive. Perhaps that makes > a difference? > > I'll redo the test case with --whole-archive (will need some fixes) --whole-archive makes the difference.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #12 from Andi Kleen --- Okay. I only compared gcc-7 (working) vs gcc-9 (broken), but always with LTO. Looking at the kernel link it also uses --whole-archive. Perhaps that makes a difference? I'll redo the test case with --whole-archive (will need some fixes)
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #11 from H.J. Lu --- (In reply to Andi Kleen from comment #9) > I think the STB_SECONDARY stuff is only needed if ld -r is used, but not for > ar Linker won't search archive to resolve weak definition. Since SECONDARY is between WEAK and undefined, linker will keep searching archive for strong definition to override secondary definition.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #10 from H.J. Lu --- (In reply to Andi Kleen from comment #8) > It works fine without LTO. > > Otherwise the Linux kernel wouldn't work. It relies on this behavior for its > syscalls. > [hjl@gnu-cfl-2 pr95928]$ make /usr/gcc-9.3.1-x32/bin/gcc -B./-c -o dummy.o dummy.c /usr/gcc-9.3.1-x32/bin/gcc -B./ -c sys_ni.i /usr/gcc-9.3.1-x32/bin/gcc -B./ -c capability.i /usr/gcc-9.3.1-x32/bin/gcc-ar rc -o libx.a sys_ni.o capability.o /usr/gcc-9.3.1-x32/bin/gcc -B./ -O2 -o x dummy.o libx.a /usr/gcc-9.3.1-x32/bin/gcc -B./ -O2 -o y dummy.o sys_ni.o capability.o objdump --disassemble=__x64_sys_capget x | grep sys_ni_syscall 401127: e8 e5 ff ff ff callq 40 objdump --disassemble=__x64_sys_capget y | grep sys_ni_syscall make: *** [Makefile:20: all] Error 1 [hjl@gnu-cfl-2 pr95928]$ > The test case is extracted from there. Something is missing in this testcase.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #9 from Andi Kleen --- I think the STB_SECONDARY stuff is only needed if ld -r is used, but not for ar
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #8 from Andi Kleen --- It works fine without LTO. Otherwise the Linux kernel wouldn't work. It relies on this behavior for its syscalls. The test case is extracted from there.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #7 from H.J. Lu --- (In reply to H.J. Lu from comment #6) > It has nothing to do with LTO. You get the same behavior without LTO. > This is how weak symbol works. BTW, this is why I proposed STB_SECONDARY: https://gcc.gnu.org/legacy-ml/gcc/2012-06/msg00390.html
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 H.J. Lu changed: What|Removed |Added CC||hjl.tools at gmail dot com --- Comment #6 from H.J. Lu --- It has nothing to do with LTO. You get the same behavior without LTO. This is how weak symbol works.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #5 from Andi Kleen --- It doesn't seem to be the plugin itself, I compiled trunk with the gcc-7 lto-plugin.c and it fails too.
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #4 from Andi Kleen --- Reproduced on trunk too 11.0-200626 e74c281bf4955eea7fdc5f21b43e29fa0235a5b0
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #3 from Andi Kleen --- Versions reproduced: gcc version 10.1.1 20200507 [revision dd38686d9c810cecbaa80bb82ed91caaa58ad635] (SUSE Linux) gcc-9 (SUSE Linux) 9.3.1 20200406 [revision 6db837a5288ee3ca5ec504fbd5a765817e556ac2] Version which worked correctly: gcc version 7.5.0 (SUSE Linux) binutils: GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.34.0.20200325-1
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #1 from Andi Kleen --- Created attachment 48792 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48792&action=edit sys_ni.i
[Bug lto/95928] LTO through ar breaks weak function resolution
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95928 --- Comment #2 from Andi Kleen --- Created attachment 48793 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48793&action=edit capability.i
