https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106835
Bug ID: 106835
Summary: [i386] Taking an address of _GLOBAL_OFFSET_TABLE_
produces a wrong value
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: rui314 at gmail dot com
Target Milestone: ---
On i386, _GLOBAL_OFFSET_TABLE_ should reference the location of .got.plt.
However, the following piece of code prints out a bogus value:
```
$ cat foo.c
#include <stdio.h>
extern char _GLOBAL_OFFSET_TABLE_[];
char *ptr = _GLOBAL_OFFSET_TABLE_;
int main() {
printf("%lx\n", (unsigned long)ptr);
}
$ i686-linux-gnu-gcc-12 -m32 -c foo.c
$ i686-linux-gnu-gcc-12 -m32 -o foo foo.o
$ ./foo
ffffffd0
```
This is because the relocation for .data is of type R_386_GOTPC. It should be
R_386_32.
```
$ readelf -r foo.o
Relocation section '.rel.text' at offset 0x234 contains 5 entries:
Offset Info Type Sym. Value Symbol's Name
00000010 00000802 R_386_PC32 00000000 __x86.get_pc_thunk.ax
00000015 0000060a R_386_GOTPC 00000000 _GLOBAL_OFFSET_TABLE_
0000001b 00000509 R_386_GOTOFF 00000000 ptr
00000025 00000309 R_386_GOTOFF 00000000 .rodata
0000002d 00000904 R_386_PLT32 00000000 printf
Relocation section '.rel.data.rel' at offset 0x25c contains 1 entry:
Offset Info Type Sym. Value Symbol's Name
00000000 0000060a R_386_GOTPC 00000000 _GLOBAL_OFFSET_TABLE_
```
I found this bug when writing a test for the mold linker.
Related to: https://github.com/rui314/mold/issues/693
