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Re: [gold] 2.27 generates GOT where 2.26 did not


On 11-08-16 17:31, Jethro Beekman wrote:
> I have these two files:
> 
> // asm_var.S
> .section .rodata
> .global asm_var
> .protected asm_var
> .size asm_var, 8
> asm_var:
> 	.org .+8
> 
> // get_addr.c
> extern unsigned long asm_var;
> 
> void* get_addr() {
> 	return &asm_var;
> }
> 
> That I compile with:
> gcc -O3 -fuse-ld=gold -fPIC -shared -nostdlib -Wl,-Bsymbolic asm_var.S get_addr.c
> 
> With gold 2.26.1 (and most likely older versions as well), this results in:
> 
> 00000000000002f0 <get_addr>:
>  2f0:	48 8d 05 01 00 00 00 	lea    0x1(%rip),%rax    # 2f8 <asm_var>
>  2f7:	c3                   	retq
> 
> Yet with 2.27 this results in:
> 
> 0000000000000340 <get_addr>:
>  340:	48 8b 05 99 1c 00 00 	mov    0x1c99(%rip),%rax # 1fe0 <_DYNAMIC+0x110>
>  347:	c3                   	retq
> 
> What's at 1fe0?
> 
> 000000001fe0  000500000006 R_X86_64_GLOB_DAT 0000000000000348 asm_var + 0
> 
> Is this a regression in 2.27? I really don't want to use the GOT. Is there a
> flag I can pass to get the old behavior?

I think I found another, possibly related, regression. If I add another file "map":

{
local:
	*;
};

And compile with -Wl,--version-script,map on 2.26 I get:

DYNAMIC SYMBOL TABLE:
no symbols

But on 2.27 I get:

DYNAMIC SYMBOL TABLE:
00000000000002a8 l    D  .rodata	0000000000000008 .protected asm_var

Jethro Beekman


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