On Thu, 12 Sep 2013, Diego Biurrun wrote:
On Sun, Sep 08, 2013 at 08:09:17AM +0200, Luca Barbato wrote:
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -100,14 +100,14 @@ av_alloc_size(1, 2) static inline void
*av_malloc_array(size_t nmemb, size_t siz
* Allocate or reallocate a block of memory.
* If ptr is NULL and size > 0, allocate a new block. If
* size is zero, free the memory block pointed to by ptr.
+ * @note Pointers provided by av_malloc family of functions cannot be
+ * passed to av_realloc().
Pointers originating from the av_malloc() family of functions must not
be passed to av_realloc(). Just as with POSIX realloc(), behavior is
undefined in that case; alignment requirements may not be fulfilled,
crashes may occur.
This omits a very vital point. If you just say "just as with POSIX
realloc", you are misssing the main point. If you compare av_malloc and
av_realloc to POSIX malloc and POSIX realloc, you don't have the same
issue. You can pass malloc() pointers to realloc(), but you can't pass
av_malloc() pointers to av_realloc(), since the former can be implemented
by (posix_)memalign.
That is, the description needs to mention memalign at least in some way.
And mentioning that alignment requirements might not be kept is just
redundant and misleading from the actual point.
What about:
Pointers originating from the av_malloc() family of functions must not be
passed to av_realloc(). The former can be implemented using memalign (or
other functions), and there's no guarantee that pointers from that
function can be passed to realloc() at all - this is undefined according
to POSIX.
// Martin
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