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-rw-r--r--src/liblzma/lz/lz_decoder.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/src/liblzma/lz/lz_decoder.c b/src/liblzma/lz/lz_decoder.c
index bb21d0d0..6c9024e2 100644
--- a/src/liblzma/lz/lz_decoder.c
+++ b/src/liblzma/lz/lz_decoder.c
@@ -91,11 +91,17 @@ decode_buffer(lzma_coder *coder,
in, in_pos, in_size);
// Copy the decoded data from the dictionary to the out[]
- // buffer.
+ // buffer. Do it conditionally because out can be NULL
+ // (in which case copy_size is always 0). Calling memcpy()
+ // with a null-pointer is undefined even if the third
+ // argument is 0.
const size_t copy_size = coder->dict.pos - dict_start;
assert(copy_size <= out_size - *out_pos);
- memcpy(out + *out_pos, coder->dict.buf + dict_start,
- copy_size);
+
+ if (copy_size > 0)
+ memcpy(out + *out_pos, coder->dict.buf + dict_start,
+ copy_size);
+
*out_pos += copy_size;
// Reset the dictionary if so requested by coder->lz.code().