[Ffmpeg-devel] bfin cpu specific build options

[Marc Hoffman]

On Feb 21, 2007, at 9:28 AM, M?ns Rullg?rd wrote:

>
> Guillaume POIRIER said:
>> Hi,
>>
>> On 2/21/07, M?ns Rullg?rd <mans at mansr.com> wrote:
>>>
>>> Marc Hoffman said:
>>>> Not sure if this needs an explanation.
>>>>
>>>> Index: configure
>>>> ===================================================================
>>>> --- configure        (revision 8047)
>>>> +++ configure        (working copy)
>>>> @@ -1329,6 +1329,11 @@
>>>>          sparc64)
>>>>              add_cflags "-mcpu=v9"
>>>>          ;;
>>>> +        bf*) #bf531 bf532 bf533 bf561 bf5xx all get this config
>>>> +            add_cflags "-mfdpic"
>>>> +            add_ldflags "-mfdpic"
>>>> +            add_ldflags "-Wl,--defsym,__stacksize=0x40000"
>>>> +            ;;
>>>
>>> The ;; indentation is inconsistent.  Otherwise OK.  I don't know  
>>> blackfin,
>>> so I assume the options are correct.
>>
>> I'm curious about the necessity of specifying stack size value. Is
>> this meant to optimize better, or is it necessary to just get ffmpeg
>> to compile and run correctly?
>
> That flag defines the symbol __stacksize as having the address, not  
> value,
> 0x40000.  Presumably, there is a declaration such as extern long  
> __stacksize;
> in some header, but no actual definition in any source file.  One  
> can only
> hope that the loader actually store the stack size at this location.

To answer the stacksize issue, the ffmpeg allocates the audio buffer  
on the stack and that just happens to be 128k which is the default  
stack size.  As Mans points out stacksize is just a symbol which is  
defined by the liner environment.

Do you need me to fix the indentation?

Thanks
Marc