[Ffmpeg-devel] Mac OS X Intel last part: balign directives

Luca Abeni lucabe72
Thu Aug 10 10:12:19 CEST 2006

Hi John,

On Thu, 2006-08-10 at 17:45 +1000, John Dalgliesh wrote:
> Hello list,
> Looking for a bit of direction on this last bit of the patch: problem 
> being that Apple's as does not recognise '.balign'. I am aware of previous 
> determinations on this issue, e.g.: 
> <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2006-February/007645.html>
I see that mplayer contains an "asmalign.h" file defining macros for
solving this issue, but it uses "#ifdef SYS_DARWIN" which (if I
understand well) is not the way to go.

I think Rich Felker described the correct solution:
The solution is to make a test in configure to test the behavior of
align. First try assembling a file with .balign or .p2align. If one
fails try the other. If both fail, first try .align 3. This will fail
if .align takes its argument in bytes rather than as the number of low
bits that must be zero; if it does try .align 8. If they all fail,
disable alignment altogether and hope it's not needed. :) Then include
a definition of BALIGN_8 and BALIGN_16 in config.h.

So, configure should write the right "#define ASMALIGN8  ..." and
"#define ASMALIGN16 ..." in config.h

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