Bug#958783: clang-10: -rtlib=compiler-rt fails with undefined symbol: _Unwind_Resume

[Sylvestre Ledru]

Le 25/04/2020 à 10:48, Sylvestre Ledru a écrit :

Package: clang-10
Version: 1:10.0.0-4
Severity: normal

Dear Maintainer,

With
---
#include <iostream>
int main(int argc, char **argv) {
   std::cout << "Hello World" << std::endl;
   return 0;
}
---

clang++-10 -fuse-ld=lld -rtlib=compiler-rt -stdlib=libc++ foo.cpp
ld.lld: error: undefined symbol: _Unwind_Resume

referenced by foo.cpp
               /tmp/foo-81c51b.o:(std::__1::basic_ostream<char, std::__1::char_traits<char> >& 
std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, 
std::__1::char_traits<char> >&, char const*, unsigned long))
referenced by foo.cpp
               /tmp/foo-81c51b.o:(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > 
std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, 
std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char))
referenced by foo.cpp
               /tmp/foo-81c51b.o:(std::__1::basic_ios<char, 
std::__1::char_traits<char> >::widen(char) const)

clang: error: linker command failed with exit code 1 (use -v to see invocation)


But the following works:
clang++-10 -fuse-ld=lld -rtlib=compiler-rt foo.cpp
clang++-10 -fuse-ld=lld -stdlib=libc++ foo.cpp

I guess it is because compiler-rt is built with the option:
-DCOMPILER_RT_USE_LIBCXX=NO

Actually, the option to provide is -DLIBCXXABI_USE_LLVM_UNWINDER=YES to build 
libc++abi and add libunwind-dev as a build dep

I will see to activate it by default in the pacakge.


Sylvestre