[PATCH] D41551: [ELF] - Allow relocation to a weak undefined symbol when -z notext is given.

[George Rimar via Phabricator via llvm-commits]

grimar added a comment.

Ok, I think GNU linkers do correct thing. We also should produce the relocation for week undefined when building shared library.
Imagine next code:

dso.c:

  extern __attribute__((visibility("default"), weak)) unsigned long long foo();
  unsigned long long func() {
    return &foo;
  }
  unsigned long long run() {
   return func();
  }

main.c:

  unsigned long long run();
  
  unsigned long long foo() {
   return 1;
  }
  
  int main() {
   return run() > 0 ? 1 : 0;
  }

If we do not produce the relocation for week undefined `foo` when linkind DSO, code would work incorrectly:

  ~/LLVM/build/bin/clang -o dso dso.c -shared -fuse-ld=lld -O0 -z notext
  ~/LLVM/build/bin/clang -o main main.c dso -fuse-ld=lld -O0
  ./main 
  echo $?
  0

Output should be 1.

I'll update the patch and testcase.


https://reviews.llvm.org/D41551