[Bug gold/28876] New: gold should error out when creating a direct reference to protected function

[thiago at kde dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28876

            Bug ID: 28876
           Summary: gold should error out when creating a direct reference
                    to protected function
           Product: binutils
           Version: 2.38
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gold
          Assignee: ccoutant at gmail dot com
          Reporter: thiago at kde dot org
                CC: ian at airs dot com
  Target Milestone: ---

Related to #28875

Given library:

$ cat libb2.cpp           
__attribute__((visibility("protected"))) long internal_i = 0;
__attribute__((visibility("protected"))) long internal_f()
{
    return 2;
}
$ gcc -shared -fPIC -o libb.so libb2.cpp
$ eu-readelf --dyn-syms libb.so| grep internal
    5: 0000000000004028      8 OBJECT  GLOBAL PROTECTED     22 internal_i
    6: 00000000000010f9     11 FUNC    GLOBAL PROTECTED     11 _Z10internal_fv

gold already produces an error if it would need to create a copy relocation for
the variable:

$ cat main.cpp 
extern __attribute__((visibility("default"))) long internal_i;
extern __attribute__((visibility("default"))) long internal_f();

int main()
{
    internal_i = (long) &internal_f;
}
$ gcc -fuse-ld=gold main.cpp libb.so
/usr/bin/ld.gold: error: /tmp/ccg0cNpy.o: cannot make copy relocation for
protected symbol 'internal_i', defined in libb.so
collect2: error: ld returned 1 exit status

However, it does not for the function address:

$ cat main.cpp 
extern __attribute__((visibility("default"))) long internal_f();

int main()
{
    return (long) &internal_f;
}
$ gcc -fuse-ld=gold main.cpp libb.so                              
$ objdump --no-show -Cdr a.out| sed -n '/<main>:/,/^$/p'
00000000004005e6 <main>:
  4005e6:       push   %rbp
  4005e7:       mov    %rsp,%rbp
  4005ea:       mov    $0x4004f0,%eax
  4005ef:       pop    %rbp
  4005f0:       ret

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