[llvm-bugs] [Bug 34301] New: lld drops the weak symbol

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Aug 23 14:00:30 PDT 2017


            Bug ID: 34301
           Summary: lld drops the weak symbol
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: ELF
          Assignee: unassignedbugs at nondot.org
          Reporter: sylvestre at debian.org
                CC: davide at freebsd.org, joker.eph at gmail.com,
                    llvm-bugs at lists.llvm.org, ruiu at google.com

Reported here: 

here's what main looks like in that dummy:
00000000002010f8 <main>:
  2010f8:       31 c0                   xor    %eax,%eax
  2010fa:       e9 01 ef df ff          jmpq   0
  2010ff:       cc                      int3   

Here's what it's expected to look like:
00000000000006e0 <main>:
 6e0:   55                      push   %rbp
 6e1:   48 89 e5                mov    %rsp,%rbp
 6e4:   b8 00 00 00 00          mov    $0x0,%eax
 6e9:   e8 b2 fe ff ff          callq  5a0 <print_status at plt>
 6ee:   5d                      pop    %rbp
 6ef:   c3                      retq   

And dummy.c is:
extern __attribute__((visibility("default"), weak)) int print_status();

int main() {
    return print_status();

This is what objdump -dr dummy.o looks like on my machine:
0000000000000000 <main>:
   0:   55                      push   %rbp
   1:   48 89 e5                mov    %rsp,%rbp
   4:   b8 00 00 00 00          mov    $0x0,%eax
   9:   e8 00 00 00 00          callq  e <main+0xe>
                        a: R_X86_64_PLT32       print_status-0x4
   e:   5d                      pop    %rbp
   f:   c3                      retq   

And what it looks like on yours:
0000000000000000 <main>:
   0:   31 c0                   xor    %eax,%eax
   2:   e9 00 00 00 00          jmpq   7 <main+0x7>
                        3: R_X86_64_PLT32       print_status-0x4

The code is fine, but lld is completely dropping the weak symbol.

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