libavutil: Use an intermediate variable in AV_COPY*U
authorMartin Storsjö <martin@martin.st>
Thu, 28 Jul 2016 11:30:25 +0000 (14:30 +0300)
committerMartin Storsjö <martin@martin.st>
Sun, 31 Jul 2016 19:50:55 +0000 (22:50 +0300)
If AV_RN and AV_WN are macros with multiple individual reads and
writes, the previous version of the AV_COPYU macro would fail if
the reads and writes overlap.

This should not be any less efficient in any case, given a
sensibly optimizing compiler.

Signed-off-by: Martin Storsjö <martin@martin.st>
libavutil/intreadwrite.h

index f77fd60..cdf1ef4 100644 (file)
@@ -467,7 +467,11 @@ union unaligned_16 { uint16_t l; } __attribute__((packed)) av_alias;
  * memory locations.
  */
 
-#define AV_COPYU(n, d, s) AV_WN##n(d, AV_RN##n(s));
+#define AV_COPYU(n, d, s)                                       \
+    do {                                                        \
+        uint##n##_t val = AV_RN##n(s);                          \
+        AV_WN##n(d, val);                                       \
+    } while (0)
 
 #ifndef AV_COPY16U
 #   define AV_COPY16U(d, s) AV_COPYU(16, d, s)