Commit a9793feacefac6d44b761bed12566029f5811063
2023-08-15T11:30:26
[base] Avoid UB with memcpy `FT_NEW_ARRAY(p, 0)` sets `p` to `NULL`. `FT_Stream_ReadAt` with a memory based stream uses `FT_MEM_COPY` which is `memcpy` which specifies that it is undefined behavior for either the `src` or `dst` to be `NULL`. Instead of forcing all callers work around calling `FT_Stream_Read` when `buffer == NULL && count == 0` do the check in `FT_StreamRead`. This allows any call with `count == 0` to succesfully read zero bytes without UB. * src/base/ftstream.c (FT_Stream_ReadAt): skip `FT_MEM_COPY` when `count == 0`. (FT_Stream_TryRead): ditto Fixes: #1250
diff --git a/src/base/ftstream.c b/src/base/ftstream.c
index 05c5637..64826ac 100644
--- a/src/base/ftstream.c
+++ b/src/base/ftstream.c
@@ -141,7 +141,9 @@
if ( read_bytes > count )
read_bytes = count;
- FT_MEM_COPY( buffer, stream->base + pos, read_bytes );
+ /* Allow "reading" zero bytes without UB even if buffer is NULL */
+ if ( count )
+ FT_MEM_COPY( buffer, stream->base + pos, read_bytes );
}
stream->pos = pos + read_bytes;
@@ -178,7 +180,9 @@
if ( read_bytes > count )
read_bytes = count;
- FT_MEM_COPY( buffer, stream->base + stream->pos, read_bytes );
+ /* Allow "reading" zero bytes without UB even if buffer is NULL */
+ if ( count )
+ FT_MEM_COPY( buffer, stream->base + stream->pos, read_bytes );
}
stream->pos += read_bytes;