[FFmpeg-cvslog] libavutil: document side effects of macros

[Christophe Gisquet]

ffmpeg | branch: master | Christophe Gisquet <christophe.gisquet at gmail.com> | Thu Jul 10 20:49:06 2014 +0200| [8da1defe6986aab8506203c6e12f44d4df62672e] | committer: Michael Niedermayer

libavutil: document side effects of macros

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=8da1defe6986aab8506203c6e12f44d4df62672e
---

 libavutil/intreadwrite.h |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libavutil/intreadwrite.h b/libavutil/intreadwrite.h
index 7ee6977..51fbe30 100644
--- a/libavutil/intreadwrite.h
+++ b/libavutil/intreadwrite.h
@@ -50,6 +50,14 @@ typedef union {
  * AV_[RW][BLN](16|24|32|48|64) and AV_(COPY|SWAP|ZERO)(64|128) macros.
  * Preprocessor symbols must be defined, even if these are implemented
  * as inline functions.
+ *
+ * R/W means read/write, B/L/N means big/little/native endianness.
+ * The following macros require aligned access, compared to their
+ * unaligned variants: AV_(COPY|SWAP|ZERO)(64|128), AV_[RW]N[8-64]A.
+ * Incorrect usage may range from abysmal performance to crash
+ * depending on the platform.
+ *
+ * The unaligned variants are AV_[RW][BLN][8-64] and AV_COPY*U.
  */
 
 #ifdef HAVE_AV_CONFIG_H