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Bug 925024

Summary: sys-libs/llvm-libunwind-18.1.0_rc2: /usr/lib64/libc++abi.so.1: undefined symbol: __deregister_frame_info
Product: Gentoo Linux Reporter: Jonas Rakebrandt <xarblu>
Component: Current packagesAssignee: LLVM support project <llvm>
Status: RESOLVED UPSTREAM    
Severity: normal CC: parona, xarblu
Priority: Normal    
Version: unspecified   
Hardware: AMD64   
OS: Linux   
See Also: https://github.com/llvm/llvm-project/issues/83080
Whiteboard:
Package list:
Runtime testing required: ---
Bug Depends on:    
Bug Blocks: 830404    
Attachments: build.log

Description Jonas Rakebrandt 2024-02-20 00:40:55 UTC
On a full LLVM system (incl. libc++) llvm-libunwind-18.1.0_rc2 breaks *everything* linked against libc++ at runtime. Not entirely sure why this happens because there is no such issue with 17.0.6. As far as I understand __deregister_frame_info is an external function from libc so maybe there's a linking issue somewhere.


Reproducible: Always

Steps to Reproduce:
I tested builds with an ENV of *FLAGS="-O2 -march=native -pipe" with both a known working LLVM 17.0.6 stack and a full 18.1.0_rc2 stack.
(LD_PRELOAD was used because fully merging the package breaks *everything* using libc++ for me which makes recovery *very* annoying if you don't have a working binpkg or snapshot.)

1. ebuild /var/db/repos/gentoo/sys-libs/llvm-libunwind/llvm-libunwind-18.1.0_rc2.ebuild clean install
2. LD_PRELOAD=/var/tmp/portage/sys-libs/llvm-libunwind-18.1.0_rc2/image/usr/lib64/libunwind.so.1.0 clang --version
Actual Results:  
clang: symbol lookup error: /usr/lib64/libc++abi.so.1: undefined symbol: __deregister_frame_info

Expected Results:  
Normal clang --version output

Running toolchain as selected by "default/linux/amd64/17.1/systemd/clang/merged-usr" profile. I will provide the build log in an attachment. I will skip emerge --info for now as all (interesting) flags are changed by the aforementioned package.env anyways.
Comment 1 Jonas Rakebrandt 2024-02-20 00:41:28 UTC
Created attachment 885478 [details]
build.log
Comment 2 Alfred Wingate 2024-02-21 01:49:03 UTC
This is a symbol that the libc should have.

I have a llvm-18 machine and I havent encountered this issue.

$ objdump -T --demangle /lib/libc.so.6 | grep __deregister_frame_info
0016db70 g    DF .text  0000013d  GCC_3.0     __deregister_frame_info_bases
0016dcb0 g    DF .text  00000005  GLIBC_2.0   __deregister_frame_info

=================================================================
                        Package Settings
=================================================================

sys-devel/clang-common-18.1.0_rc2::gentoo was built with the following:
USE="(default-compiler-rt) (default-libcxx) (default-lld) hardened (llvm-libunwind) -bootstrap-prefix -verify-sig" ABI_X86="(64)"


sys-libs/llvm-libunwind-18.1.0_rc2::gentoo was built with the following:
USE="(clang) debug static-libs -test -verify-sig" ABI_X86="32 (64) (-x32)"
CFLAGS="-O2 -pipe -ggdb3"
CXXFLAGS="-O2 -pipe -ggdb3"
FEATURES="binpkg-docompress qa-unresolved-soname-deps ebuild-locks splitdebug userfetch binpkg-logs pid-sandbox preserve-libs split-elog network-sandbox protect-owned sfperms warn-on-large-env unmerge-orphans usersync parallel-fetch binpkg-multi-instance binpkg-dostrip pkgdir-index-trusted strict news assume-digests buildpkg-live compress-build-logs distlocks xattr userpriv usersandbox candy split-log unmerge-logs config-protect-if-modified merge-sync strict-keepdir sandbox fixlafiles parallel-install multilib-strict clean-logs unknown-features-warn ipc-sandbox compressdebug"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--as-needed -Wl,--defsym=__gentoo_check_ldflags__=0 -ggdb3"


sys-libs/libcxx-18.1.0_rc2::gentoo was built with the following:
USE="(clang) (libcxxabi) static-libs -test -verify-sig" ABI_X86="32 (64) (-x32)"
CFLAGS="-O2 -pipe -ggdb3"
CXXFLAGS="-O2 -pipe -ggdb3"
FEATURES="binpkg-docompress qa-unresolved-soname-deps ebuild-locks splitdebug userfetch binpkg-logs pid-sandbox preserve-libs split-elog network-sandbox protect-owned sfperms warn-on-large-env unmerge-orphans usersync parallel-fetch binpkg-multi-instance binpkg-dostrip pkgdir-index-trusted strict news assume-digests buildpkg-live compress-build-logs distlocks xattr userpriv usersandbox candy split-log unmerge-logs config-protect-if-modified merge-sync strict-keepdir sandbox fixlafiles parallel-install multilib-strict clean-logs unknown-features-warn ipc-sandbox compressdebug"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--as-needed -Wl,--defsym=__gentoo_check_ldflags__=0 -ggdb3"


sys-libs/libcxxabi-18.1.0_rc2::gentoo was built with the following:
USE="(clang) static-libs -test -verify-sig" ABI_X86="32 (64) (-x32)"
CFLAGS="-O2 -pipe -ggdb3"
CXXFLAGS="-O2 -pipe -ggdb3"
FEATURES="binpkg-docompress qa-unresolved-soname-deps ebuild-locks splitdebug userfetch binpkg-logs pid-sandbox preserve-libs split-elog network-sandbox protect-owned sfperms warn-on-large-env unmerge-orphans usersync parallel-fetch binpkg-multi-instance binpkg-dostrip pkgdir-index-trusted strict news assume-digests buildpkg-live compress-build-logs distlocks xattr userpriv usersandbox candy split-log unmerge-logs config-protect-if-modified merge-sync strict-keepdir sandbox fixlafiles parallel-install multilib-strict clean-logs unknown-features-warn ipc-sandbox compressdebug"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--as-needed -Wl,--defsym=__gentoo_check_ldflags__=0 -ggdb3"
Comment 3 Jonas Rakebrandt 2024-02-21 19:14:23 UTC
(In reply to Alfred Wingate from comment #2)

> I have a llvm-18 machine and I havent encountered this issue.

Hm, weird. I can consistently reproduce this issue on 2 different machines.

> $ objdump -T --demangle /lib/libc.so.6 | grep __deregister_frame_info
> 0016db70 g    DF .text  0000013d  GCC_3.0     __deregister_frame_info_bases
> 0016dcb0 g    DF .text  00000005  GLIBC_2.0   __deregister_frame_info

For me this returns:

001734d0 g    DF .text  00000150  GCC_3.0     __deregister_frame_info_bases
00173620 g    DF .text  00000005  GLIBC_2.0   __deregister_frame_info

...which should be fine (?). Not entirely sure how to interpret the different numbers. I'm assuming they're just memory offsets to where the symbols are in the .so.

A little more info on what versions are broken for me:
- 16.0.6 (just for experimenting) same as 17.0.6
- 17.0.6 works no matter what flags I give clang (within reason of course)
- 18.1.0_rc2 is broken, even with very basic (-O2 -pipe) or no flags at all
- 19.0.0_pre20240218 (just for experimenting) same as 18.1.0_rc2

The fact that I can rebuild <=17.0.6 any way I want and it works as expected leads me to believe that it's not an issue with my toolchain/glibc and rather something introduced from 17 to 18.
Comment 4 Jonas Rakebrandt 2024-02-23 13:02:54 UTC
Did a little more testing and the whole thing works when also preloading libgcc_s.

Tested the same way as previously but with libgcc_s this time:

LD_PRELOAD=/usr/lib/gcc/x86_64-pc-linux-gnu/13/libgcc_s.so.1:/var/tmp/portage/sys-libs/llvm-libunwind-18.1.0_rc3/image/usr/lib64/libunwind.so.1.0 clang --version

Does that mean ld.so just doesn't load / libunwind.so.1.0 doesn't set all needed libraries?
Comment 5 Jonas Rakebrandt 2024-02-26 22:48:21 UTC
Finally tracked this whole thing down to https://github.com/llvm/llvm-project/commit/5eb44df1b64dbd1a86b099128092a7fd2001c0ba

Building llvm-libunwind with MYCMAKEARGS="-DLIBUNWIND_ENABLE_FRAME_APIS=ON" makes all the symbols found.

Not sure if this should just be set unconditionally as the commit itself says:

> Default this to on, so as not to remove the apis from
> environments that already have them.

...and then has the actual default set to OFF.
Maybe I'm just misunderstanding the commit message but could be bug.
Comment 6 Sam James archtester Gentoo Infrastructure gentoo-dev Security 2024-02-26 23:00:14 UTC
I haven't looked at it in detail, but given you're hitting a problem that is related to the commit, and the inconsistency b/t commit msg + what it does, I think it's fine if you file a bug upstream & CC the author/reviewer.

Normally I'd just comment on the review for something like this first but it was on Phab which is now archived.
Comment 7 Jonas Rakebrandt 2024-02-26 23:27:01 UTC
Created an upstream issue here: https://github.com/llvm/llvm-project/issues/83080
Comment 8 Sam James archtester Gentoo Infrastructure gentoo-dev Security 2024-02-26 23:28:37 UTC
Thanks!
Comment 9 Jonas Rakebrandt 2024-02-29 13:15:35 UTC
Turned out to be mold issue fixed in https://github.com/rui314/mold/commit/50bdf39ba57e29386de28bd0c303035e626fa29c

Marking this as resolved upstream.