Thanks. But why "vvvvv" is linked correctly here? Shouldn't it be treated as static with -fwhole-program?
Bingfeng > -----Original Message----- > From: Richard Guenther [mailto:richard.guent...@gmail.com] > Sent: 08 June 2010 14:10 > To: Bingfeng Mei > Cc: Jan Hubicka; gcc@gcc.gnu.org; Cary Coutant > Subject: Re: externally_visible and resoultion file > > On Tue, Jun 8, 2010 at 3:01 PM, Bingfeng Mei <b...@broadcom.com> wrote: > > Hi, > > Sorry for coming back to this issue after a while. I am still puzzled > > by this. 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 > > > > Since you both mentioned that 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, and vvvvvv is > > linked correctly though. > > > > 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) > > > > Is this a bug? GCC should issue warning/error here. Why is vvvvvv > linked correctly? > > Shouldn't it be treated as static with -fwhile-program and without > externally_visible? > > bar should be indeed eliminated which is what I see with not > using the linker plugin. > > If you use the linker-plugin I see in the .optimized dump that > the were eliminated. But it seems that gold picks them up > from the original objects which seem to be retained somehow. > > I guess this is a bug in the linker-plugin. > > Richard. > > > My trunk is 160104 by the way.
