1 files changed, 39 insertions, 3 deletions

diff --git a/innobase/row/row0mysql.c b/innobase/row/row0mysql.c
index 841d03acc48..d6c8d7ab412 100644
--- a/innobase/row/row0mysql.c
+++ b/innobase/row/row0mysql.c
@@ -28,6 +28,9 @@ Created 9/17/2000 Heikki Tuuri
 #include "rem0cmp.h"
 #include "log0log.h"
 
+/* A dummy variable used to fool the compiler */
+ibool	row_mysql_identically_false	= FALSE;
+
 /* List of tables we should drop in background. ALTER TABLE in MySQL requires
 that the table handler can drop the table in background when there are no
 queries to it any more. Protected by the kernel mutex. */
@@ -63,15 +66,48 @@ row_mysql_store_blob_ref(
 	byte*	dest,		/* in: where to store */
 	ulint	col_len,	/* in: dest buffer size: determines into
 				how many bytes the BLOB length is stored,
-				this may vary from 1 to 4 bytes */
-	byte*	data,		/* in: BLOB data */
-	ulint	len)		/* in: BLOB length */
+				the space for the length may vary from 1
+				to 4 bytes */
+	byte*	data,		/* in: BLOB data; if the value to store
+				is SQL NULL this should be NULL pointer */
+	ulint	len)		/* in: BLOB length; if the value to store
+				is SQL NULL this should be 0; remember
+				also to set the NULL bit in the MySQL record
+				header! */
 {
+	ulint	sum	= 0;
+	ulint	i;
+
+	/* MySQL might assume the field is set to zero except the length and
+	the pointer fields */
+
+	memset(dest, '\0', col_len);
+
 	/* In dest there are 1 - 4 bytes reserved for the BLOB length,
 	and after that 8 bytes reserved for the pointer to the data.
 	In 32-bit architectures we only use the first 4 bytes of the pointer
 	slot. */
 
+	ut_a(col_len - 8 > 1 || len < 256);
+	ut_a(col_len - 8 > 2 || len < 256 * 256);
+	ut_a(col_len - 8 > 3 || len < 256 * 256 * 256);
+
+	/* We try to track an elusive bug which probably was fixed
+	May 9, 2002, but better be sure: we probe the data buffer
+	to make sure it is in valid allocated memory */
+
+	for (i = 0; i < len; i++) {
+
+		sum += (ulint)(data + i);
+	}
+
+	/* The variable below is identically false, we just fool the
+	compiler to not optimize away our loop */
+	if (row_mysql_identically_false) {
+
+		printf("Sum %lu\n", sum);
+	}
+
 	mach_write_to_n_little_endian(dest, col_len - 8, len);
 
 	ut_memcpy(dest + col_len - 8, (byte*)&data, sizeof(byte*));