Date: Fri, 29 Jan 2021 12:53:49 -0800 From: Fangrui Song <i@...kray.me> To: Jiahao XU <Jiahao_XU@...look.com> Cc: "musl@...ts.openwall.com" <musl@...ts.openwall.com>, Szabolcs Nagy <nsz@...t70.net> Subject: Re: Can’t build musl with lto=thin On Fri, Jan 29, 2021 at 12:04 PM Szabolcs Nagy <nsz@...t70.net> wrote: > > * Jiahao XU <Jiahao_XU@...look.com> [2021-01-29 12:19:42 +0000]: > > musl-1.2.2 compilation with clang-11 failed to build libc.so at the final linking stage: > > ld.lld: error: undefined hidden symbol: __dls2 > > >>> referenced by ld-temp.o > > >>> lto.tmp:(_dlstart_c) > > >>> did you mean: __dls3 > > >>> defined in: lto.tmp > > > looks like a clang bug if -flto changes behaviour, doesn't it? https://www.openwall.com/lists/musl/2020/12/27/25 Clang tracks undefined symbols in module-level inline asm but does not know undefined symbols in function-scope inline asm. I don't know whether it makes sense to track function-scope inline asm - it requires to scan every instruction in the bitcode file which is a heavy operation and it is only relevant in this narrow usage. If you build this file with LTO, the LTO backend will internalize __dls2 and cause a subsequent "undefined reference" error unless you specify -u __dls2 to mark __dls2 as "visibible to a regular object file" (a workaround) > > > > > I am using CFLAGS=‘-march=native -mtune=native -Oz -flto -fmerge-all-constants -fomit-frame-pointer’ and LDFLAGS=‘-flto -fuse-ld=lld -Wl,—plugin-opt=O3,-O3,—icf=safe’. > > No configure option is supplied. > > > > Get Outlook for iOS<https://aka.ms/o0ukef>
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