Apply "alloc_size" attribute to av_alloc, av_realloc and av_mallocz

Originally committed as revision 12499 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/mem.h

@@ -48,6 +48,12 @@
     #define av_malloc_attrib
 #endif
 
+#if defined (__GNUC__) && (__GNU__ > 4 || __GNU__ == 4 && __GNU_MINOR__ > 1)
+    #define av_alloc_size(n) __attribute__((alloc_size(n)))
+#else
+    #define av_alloc_size(n)
+#endif
+
 /**
  * Allocate a block of \p size bytes with alignment suitable for all
  * memory accesses (including vectors if available on the CPU).
@@ -56,7 +62,7 @@
  * it.
  * @see av_mallocz()
  */
-void *av_malloc(unsigned int size) av_malloc_attrib;
+void *av_malloc(unsigned int size) av_malloc_attrib av_alloc_size(1);
 
 /**
  * Allocate or reallocate a block of memory.
@@ -70,7 +76,7 @@ void *av_malloc(unsigned int size) av_malloc_attrib;
  * reallocate or the function is used to free the memory block.
  * @see av_fast_realloc()
  */
-void *av_realloc(void *ptr, unsigned int size);
+void *av_realloc(void *ptr, unsigned int size) av_alloc_size(2);
 
 /**
  * Free a memory block which has been allocated with av_malloc(z)() or
@@ -91,7 +97,7 @@ void av_free(void *ptr);
  * it.
  * @see av_malloc()
  */
-void *av_mallocz(unsigned int size) av_malloc_attrib;
+void *av_mallocz(unsigned int size) av_malloc_attrib av_alloc_size(1);
 
 /**
  * Duplicate the string \p s.