On Tue, Feb 3, 2015 at 2:19 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> On Tue, Feb 03, 2015 at 02:03:14PM -0800, H.J. Lu wrote:
>> So we aren't SYMBOL_REF_EXTERNAL_P nor
>> SYMBOL_REF_LOCAL_P. What do we reference?
>
> That is reasonable. There is no guarantee the extern weak symbol is local,
> it could very well be non-local. All that you know about the symbols is
> that its address is non-NULL in that case.
>
This may be true for shared library. But it isn't true for PIE:
[hjl@gnu-6 copyreloc-3]$ cat x.c
__attribute__((weak))
int a;
extern void bar (void);
int main()
{
if (a != 0)
__builtin_abort();
bar ();
if (a != 30)
__builtin_abort();
return 0;
}
[hjl@gnu-6 copyreloc-3]$ cat bar.c
int a = -1;
void
bar ()
{
a = 30;
}
[hjl@gnu-6 copyreloc-3]$ make
gcc -pie -O3 -g -fuse-ld=gold -fpie -c x.i
gcc -pie -O3 -g -fuse-ld=gold -fpic -c -o bar.o bar.c
gcc -pie -shared -o libbar.so bar.o
gcc -pie -O3 -g -fuse-ld=gold -o x x.o libbar.so -Wl,-R,.
./x
[hjl@gnu-6 copyreloc-3]$
Even if a common symbol, a, is weak, all references to
a within PIE is local.
--
H.J.
