The following are two test files:
a.c
#include <string.h>
#include <stdio.h>
extern int foo(int);
void bar()
{
printf("bar\n");
}
extern int src[], dst[];
int vvvvvv;
int main()
{
int ret;
vvvvvv = 12;
ret = foo(20);
memcpy(dst, src, 100);
return ret + 3;
}
b.c
#include <stdio.h>
int src[100];
int dst[100];
extern int vvvvvv;
extern void bar();
int foo(int c)
{
printf("Hello world: %d\n", c);
bar();
return 1000 + vvvvvv;
}
I compiled with following steps
~/work/install-x86/bin/gcc -flto a.c -O2 -c
~/work/install-x86/bin/gcc b.c -O2 -c
ar cru libb.a b.o
~/work/install-x86/bin/gcc -flto a.o -L. -lb -O2 -fuse-linker-plugin -o f
-fwhole-program -save-temps
Currently resolution file is not used to replace externally_visible attribute
yet, I expect there will be link errors regarding both vvvvvv and bar. Somehow,
GCC doesn't complain at all. However, looking at generated assembly code, GCC
produces wrong code for calling bar. vvvvvv is linked correctly but it
shouldn't be.
0000000000400510 <foo>:
400510: 48 83 ec 08 sub $0x8,%rsp
400514: 89 fe mov %edi,%esi
400516: 31 c0 xor %eax,%eax
400518: bf 1c 06 40 00 mov $0x40061c,%edi
40051d: e8 56 01 00 00 callq 400678 <pri...@plt>
400522: 31 c0 xor %eax,%eax
400524: e8 d7 fa bf ff callq 0 <__fini_array_end> <--------
should
call bar.
400529: 8b 05 a1 17 00 00 mov 0x17a1(%rip),%eax #
401cd0 <vvvvvv>
40052f: 48 83 c4 08 add $0x8,%rsp
400533: 05 e8 03 00 00 add $0x3e8,%eax
400538: c3 retq
400539: 0f 1f 80 00 00 00 00 nopl 0x0(%rax)
My GOLD version is 2.20.51 & GCC is trunk.
I discussed with Richard Guenther. He believed this is a bug of GOLD.
--
Summary: GOLD wrongly linked function/var that are converted to
static by GCC LTO
Product: binutils
Version: 2.20
Status: NEW
Severity: normal
Priority: P2
Component: gold
AssignedTo: ian at airs dot com
ReportedBy: bmei at broadcom dot com
CC: bug-binutils at gnu dot org
http://sourceware.org/bugzilla/show_bug.cgi?id=11683
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