Re: please, help me with libffi on iOS porting

[cowwoc <cowwoc@bbs.darktech.org>]

Andrew Haley wrote:
> 
> On 08/15/2012 03:30 AM, cowwoc wrote:
>> 
>> Andrew Haley wrote:
>>>
>>>> to have 4 bytes alignment.  So is there a reason the alignment is
>>>> set to 1 byte?
>>>
>>> The doc says:
>>>
>>> `.align EXPRESSION [, EXPRESSION]'
>>>      This is the generic .ALIGN directive.  For the ARM however if the
>>>      first argument is zero (ie no alignment is needed) the assembler
>>>      will behave as if the argument had been 2 (ie pad to the next four
>>>      byte boundary).  This is for compatibility with ARM's own
>>>      assembler.
>>>
>> 
>> I believe you are wrong on this point.
> 
> I'm not: that is what it says.
> 
>> GNU Assembler says this:
>> http://sourceware.org/binutils/docs/as/ARM-Directives.html
>> 
>> but Apple Assembler does not:
>> https://developer.apple.com/library/mac/#documentation/developertools/Reference/Assembler/040-Assembler_Directives/asm_directives.html
>> 
>> hence the generated memory alignment is wrong.
> 
> Right, so Apple's assembler is incompatible.  The align_expression
> doesn't seem to be optional there, so we could simply change this to
> .align 2".
> 
> Andrew.
> 

Hi Andrew,

Take a look at https://github.com/jspahrsummers/libffi. It's not my
repository but it contains lots of iOS-specific patches, including the one
for .align 2.

There is even a 4 month old pull request for this specific issue:
https://github.com/atgreen/libffi/pull/19

Gili
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