[llvm-dev] libunwind, -static and -lpthread on ARM

[pawel k. via llvm-dev]

Missed info from docs its already doable via flags. Updating my knowledge
base. Hope it gets implemented soon.

Br,
Pawel

sob., 1.05.2021, 04:23 użytkownik Fangrui Song <maskray at google.com> napisał:

> On 2021-05-01, pawel k. via llvm-dev wrote:
> >Hello,
> >I may be wrong here but i was getting something like this in old vers of
> >clang.
> >
> >Id assume, pthread.a namely unwind.c is using api for unwinding thats
> >incompatible with one provided by clang libs. Prolly assumed gcc model or
> >windows api. Id check source of unwind.c and lookup+use or if absent
> >implement exception api version thats compatible with clang. We will need
> >to ask somebody else which clang lib provides this api. Documentation to
> >clang might have some hints too.
> >
> >Best regards,
> >Pawel
> >
> >sob., 1.05.2021, 03:47 użytkownik Andrei Datcu via llvm-dev <
> >llvm-dev at lists.llvm.org> napisał:
> >
> >> Hello,
> >>
> >> I'm trying to cross compile an executable that's using pthread. Target
> is
> >> armv7-linux-gnueabihf. I'm using the latest raspberry pi os as sysroot.
> >> I've managed to successfully build llvm, clang + all the runtimes and
> I'm
> >> trying to build a statically linked executable that's using as less GNU
> >> stuff as possible.
> >>
> >> clang++ -sysroot=...  -stdlib=libc++ --rtlib=compiler-rt -static
> >> -resource-dir ... -fuse-ld=lld -lc++abi -lunwind test.cpp
>
> You can use --unwindlib=libunwind.
>
> -lc++abi -lunwind are technically not in the right place.
> It is ok for ld.lld, though.
>
> >> The linker error I'm getting is:
> >>
> >> ld.lld: error: undefined symbol: _Unwind_ForcedUnwind
> >> >>> referenced by unwind.c:121
> >> >>>               unwind.o:(__pthread_unwind) in archive
> >> path-to-sysroot/usr/lib/arm-linux-gnueabihf/libpthread.a
> >>
> >> Peeking at libunwind's internals, it seems clear there's no
> >> _Unwind_ForcedUnwind built for ARM (at least not with default options).
> >> What options do I have?
>
> Pending patch adding _Unwind_ForcedUnwind for ARM EHABI
> https://reviews.llvm.org/D89570
>
> >> 1) Should I add some options when building libunwind so I get
> >> _Unwind_ForcedUnwind? I'm not sure this is even possible
> >> 2) Use libgcc?
> >>
> >> Thanks,
> >> Andrei
> >>
> >> _______________________________________________
> >> LLVM Developers mailing list
> >> llvm-dev at lists.llvm.org
> >> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>
>
> >_______________________________________________
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> >llvm-dev at lists.llvm.org
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>
>
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