On Tue, Feb 3, 2015 at 5:16 PM, H.J. Lu <hjl.to...@gmail.com> wrote: > 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:
Also, gcc and g++ are inconsistent about something even more simple: $ cat x.c int a; int main() { printf("%d\n", a); } With gcc -fPIE x.c SYMBOL_REF_LOCAL_P(op0) = false With g++ -fPIE x.c SYMBOL_REF_LOCAL_P(op0) = true Sri > > [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.