InnoDB bug fix: mem_realloc() didn't preserve the block contents

innobase/include/mem0mem.ic:
  mem_realloc(): preserve the old buffer contents

1 files changed, 15 insertions, 3 deletions

diff --git a/innobase/include/mem0mem.ic b/innobase/include/mem0mem.ic
index c250e6948ec..a51de5a5cf0 100644
--- a/innobase/include/mem0mem.ic
+++ b/innobase/include/mem0mem.ic
@@ -575,9 +575,21 @@ mem_realloc(
 	char*  	file_name,/* in: file name where called */
 	ulint 	line)  	/* in: line where called */
 {
-	mem_free(buf);
-
-	return(mem_alloc_func(n, file_name, line));
+	mem_heap_t*	heap = (mem_heap_t*)((byte*)buf
+			- MEM_BLOCK_HEADER_SIZE - MEM_FIELD_HEADER_SIZE);
+	ulint		size;
+	ut_a(heap->magic_n == MEM_BLOCK_MAGIC_N);
+	size = mem_block_get_len(heap);
+	ut_a(size > MEM_BLOCK_HEADER_SIZE + MEM_FIELD_HEADER_SIZE);
+	size -= MEM_BLOCK_HEADER_SIZE + MEM_FIELD_HEADER_SIZE;
+
+	if (n > size) {
+		void*	newbuf = memcpy(mem_alloc_func(n, file_name, line),
+					buf, size);
+		mem_free(buf);
+		buf = newbuf;
+	}
+	return(buf);
 }
 
 /**************************************************************************