H.J. Lu wrote:
> On Wed, Apr 15, 2009 at 7:34 AM, Dave Korn
> <dave.korn.cyg...@googlemail.com> wrote:
>> Jakub Jelinek wrote:
>>> On Wed, Apr 15, 2009 at 03:27:01PM +0100, Dave Korn wrote:
>>>>> It does look like a Cygwin specific issue.
>>>> Can you tell me whether Linux treats COMMON as a separate section with
>>>> its
>>>> own alignment, or otherwise takes steps to ensure it has a base alignment
>>>> that
>>>> the compiler can assume? Otherwise I expect I need to look at the cygwin
>>>> definitions of the ASM_OUTPUT_COMMON* macros.
>>> In ELF each STT_COMMON symbol has both size (st_size) and alignment
>>> (st_value) and the linker is of course required to lay out all the common
>>> symbols in a way that their alignment requirements are satisfied.
>> Ah, thanks. I think probably PE doesn't support that and will need explicit
>> .align pseudo-ops inserted in the assembly. I'm AFK for a few hours now but
>> will pursue this later tonight.
>>
>
> If your COMMON doesn't support alignment, you may need to use .bss with
> .align.
It does indeed look that way. Only ELF supports COMMON symbol alignment,
and the x86 backend just disregards it: i386_pe_asm_output_aligned_decl_common
from config/i386/winnt.c ignores the alignment parameter altogether.
That certainly means this is not a regression then. Thanks for all the
pointers, everyone.
cheers,
DaveK
