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

[Ramiro Polla]

On Tue, Oct 7, 2008 at 4:24 AM, M?ns Rullg?rd <mans at mansr.com> wrote:
> "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.

Which systems use malloc.h?

>> +#ifdef HAVE_POSIX_MEMALIGN
>> +#include <stdlib.h>
>> +#endif
>
> It is always save to #include <stdlib.h>

Now I see that the stdlib.h include comes from common.h.

And another thing, I remember there was some discussion regarding
whether we should include only the necessary files or whether it was
ok to just include common.h everywhere, but I forgot the outcome.

Is mem.c a case where it would be ok to:
-#include "common.h"
+#include "config.h"
+#include <string.h>
+#include <limits.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().

Would that be a manually entered list like is done for need_memalign?

Ramiro Polla