modernc.org/cc@v1.0.1/testdata/gcc-6.3.0/gcc/testsuite/gcc.c-torture/compile/20020303-1.c (about)

     1  /* With -fzero-initialized-in-bss, we made I a common symbol instead
     2     of a symbol in the .bss section.  Not only does that break semantics,
     3     but a common symbol can't be weak.  */
     4  
     5  int i __attribute__((weak)) = 0;