[FFmpeg-devel] [PATCH] put dispatch_tab* in .data (was Re: Build problem)

[Alexander Strange]

On Feb 11, 2009, at 11:13 AM, Diego Biurrun wrote:

> On Sun, Feb 08, 2009 at 07:10:33PM +0100, Dominik 'Rathann'  
> Mierzejewski wrote:
>> On Wednesday, 04 February 2009 at 11:00, Reimar D?ffinger wrote:
>>> On Wed, Feb 04, 2009 at 09:25:46AM +0000, M?ns Rullg?rd wrote:
>>>> Art Clarke <aclarke at xuggle.com> writes:
>>>>
>>>>> I installed yasm on our Mac build boxes today, and noticed the
>>>>> following error doing x86_64 builds:
>>>>>
>>>>>>> ld: pointer in read-only segment not allowed in slidable  
>>>>>>> image, used in dispatch_tab_sse from libavcodec/x86/fft_mmx.o
>>>>>
>>>>> I was wondering if people already knew why this occurs (a  
>>>>> perusal of
>>>>> the archives suggested not).  If I don't have yasm installed or
>>>>> available on the path the build works fine.  Any thoughts or  
>>>>> anyone
>>>>> else seeing this?
>>>>
>>>> Yes, Apple is stupid as usual.  What that error message means is  
>>>> that
>>>> it doesn't allow relocations in read-only sections, which is  
>>>> utterly
>>>> silly.
>>>
>>> Well, in that specific case it might also be because the data gets
>>> placed in .text and not .rodata on OSX, supposedly because of  
>>> alignment
>>> issues.
>>> Try changing libavcodec/x86/x86inc.asm to use .rodata or .data,  
>>> maybe
>>> one of them work...
>>
>> FWIW, the original code results in a shared library with text  
>> relocations
>> in read-only segment on x86_64. Putting dispatch_tab* in .rodata  
>> doesn't
>> change that, because both .text and .rodata end up in the same  
>> segment
>> that has READ and EXECUTE bits set. Putting dispatch_tab* in .data
>> gets rid of them. IOW, what about the attached patch?
>>
>> +++ ffmpeg-20090204/libavcodec/x86/fft_mmx.asm	2009-02-08  
>> 18:51:15.000000000 +0100
>> @@ -446,8 +446,9 @@ fft %+ n %+ %3%2:
>> %endrep
>> %undef n
>>
>> -align 8
>> +section .data
>> dispatch_tab%3%2: pointer list_of_fft
>> +section .text
>
> What about this?
>
> Diego

Removing the 'align 8' breaks Darwin again (unless you remove the  
SECTION_RODATA hack). This one fixes that; I'll apply it after  
building x86_64 again:
-------------- next part --------------
A non-text attachment was scrubbed...
Name: dispatch-tab-rodata.diff
Type: text/x-diff
Size: 464 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20090211/cc7444f7/attachment.diff>
-------------- next part --------------