[FFmpeg-devel] [PATCH] Use posix_memalign() instead of memalign()

[Måns Rullgård]

"Ramiro Polla" <ramiro.polla at gmail.com> writes:

> Hi,
>
> On Sun, Sep 28, 2008 at 10:17 AM, M?ns Rullg?rd <mans at mansr.com> wrote:
>> Diego 'Flameeyes' Petten? <flameeyes at gmail.com> writes:
>>
>>> While on GLIBC the memalign() function is declared in malloc.h, on
>>> OpenSolaris its definiton is in stdlib.h; include the file so that an
>>> implicit declaration can be avoided.
>>> ---
>>>
>>>  libavutil/mem.c |    1 +
>>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/libavutil/mem.c b/libavutil/mem.c
>>> index 960074c..da75638 100644
>>> --- a/libavutil/mem.c
>>> +++ b/libavutil/mem.c
>>> @@ -34,6 +34,7 @@
>>>  #ifdef HAVE_MALLOC_H
>>>  #include <malloc.h>
>>>  #endif
>>> +#include <stdlib.h>
>>>
>>>  /* you can redefine av_malloc and av_free in your project to use your
>>>     memory allocator. You do not need to suppress this file because the
>>
>> #including stdlib.h obviously can't do any harm, it being a standard
>> header.
>
>> There is, however, a deeper issue here: memalign() is not
>> defined by any standard, and some systems that have it provide no
>> means to free such allocations.  Is there any reason we can't use the
>> standard posix_memalign() instead?
>
> Attached patch should spark some discussion...
>

[...]

> Index: libavutil/mem.c
> ===================================================================
> --- libavutil/mem.c	(revision 15575)
> +++ libavutil/mem.c	(working copy)
> @@ -35,6 +35,10 @@
>  #include <malloc.h>
>  #endif

#include <malloc.h> wouldn't be needed with posix_memalign(), but see
below.

> +#ifdef HAVE_POSIX_MEMALIGN
> +#include <stdlib.h>
> +#endif

It is always save to #include <stdlib.h>

>  /* you can redefine av_malloc and av_free in your project to use your
>     memory allocator. You do not need to suppress this file because the
>     linker will do it automatically */
> @@ -57,8 +61,9 @@
>      diff= ((-(long)ptr - 1)&15) + 1;
>      ptr = (char*)ptr + diff;
>      ((char*)ptr)[-1]= diff;
> -#elif defined (HAVE_MEMALIGN)
> -    ptr = memalign(16,size);
> +#elif defined (HAVE_POSIX_MEMALIGN)
> +    if(posix_memalign(&ptr,16,size))
> +        ptr = NULL;

It might make sense to use memalign() as a fall-back for old BSD
systems and the like without posix_memalign().

-- 
M?ns Rullg?rd
mans at mansr.com