[Ffmpeg-devel] random crashes decoding MP3s

Rich Felker dalias
Sun Apr 2 09:09:07 CEST 2006

On Sat, Apr 01, 2006 at 08:31:43PM -0800, Jacob Meuser wrote:
> > > I tried to build ffmpeg on OpenBSD myself, and it turns out it's not
> > > as easy as it should be.  What exactly have you done to your source to
> > > make it build?
> > 
> > OK, now it builds, but only with --enable-memalign-hack.  Did you use
> > this option or disable mmx/sse?  OpenBSD appears to be missing
> > memalign() so one or the other is required.  Forcing mmx/sse without a
> > proper memalign() can very well result in random crashes.
> yes, there is no memlign() on OpenBSD.
> quoting malloc(3)
>     The allocated space is suitably aligned (after possible pointer coercion)
>     for storage of any type of object.  If the space is of pagesize or larg-
>     er, the memory returned will be page-aligned.

This text is not meaningful to what we're talking about. ISO C
requires that the return value of malloc be "suitably aligned for
storage of any type of object", but "object" is defined as in ISO C,
and this has nothing to do with the alignment requirements of various
asm constructs. A true memalign is needed..

> enabling the memalign-hack actually causes crashes all over the
> place.  I am only seeing problems decoding MP3 files.



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