Merge commit 'f935aca4'

* commit 'f935aca4':
  av_memcpy_backptr: avoid an infinite loop for back = 0
  4xm: check the return value of read_huffman_tables().

Conflicts:
	libavcodec/4xm.c
	libavutil/mem.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/4xm.c

@@ -757,8 +757,10 @@ static int decode_i_frame(FourXContext *f, const uint8_t *buf, int length)
     }
 
     prestream = read_huffman_tables(f, prestream, buf + length - prestream);
-    if (!prestream)
-        return -1;
+    if (!prestream) {
+        av_log(f->avctx, AV_LOG_ERROR, "Error reading Huffman tables.\n");
+        return AVERROR_INVALIDDATA;
+    }
 
     av_assert0(prestream <= buf + length);
 

libavutil/mem.c

@@ -323,7 +323,10 @@ static void fill32(uint8_t *dst, int len)
 void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
 {
     const uint8_t *src = &dst[-back];
-    if (back <= 1) {
+    if (!back)
+        return;
+
+    if (back == 1) {
         memset(dst, *src, cnt);
     } else if (back == 2) {
         fill16(dst, cnt);