1 files changed, 36 insertions, 2 deletions
diff --git a/storage/archive/azio.c b/storage/archive/azio.c
index 59fbe2182ee..6d088f279ac 100644
--- a/storage/archive/azio.c
+++ b/storage/archive/azio.c
@@ -37,6 +37,40 @@ void putLong(File file, uLong x);
 uLong  getLong(azio_stream *s);
 void read_header(azio_stream *s, unsigned char *buffer);
 
+/*
+  Valgrind normally gives false alarms for zlib operations, in the form of
+  "conditional jump depends on uninitialised values" etc. The reason is
+  explained in the zlib FAQ (http://www.zlib.net/zlib_faq.html#faq36):
+
+    "That is intentional for performance reasons, and the output of deflate
+    is not affected."
+
+  Also discussed on a blog
+  (http://www.sirena.org.uk/log/2006/02/19/zlib-generating-valgrind-warnings/):
+
+    "...loop unrolling in the zlib library causes the mentioned
+    “Conditional jump or move depends on uninitialised value(s)”
+    warnings. These are safe since the results of the comparison are
+    subsequently ignored..."
+
+    "the results of the calculations are discarded by bounds checking done
+    after the loop exits"
+
+  Fix by initializing the memory allocated by zlib when running under Valgrind.
+
+  This fix is safe, since such memory is only used internally by zlib, so we
+  will not hide any bugs in mysql this way.
+*/
+static void *az_allocator(void *dummy, uInt items, uInt size)
+{
+  return my_malloc((size_t)items*(size_t)size, IF_PURIFY(MY_ZEROFILL, MYF(0)));
+}
+
+static void az_free(void *dummy, void *address)
+{
+  my_free(address, MYF(MY_ALLOW_ZERO_PTR));
+}
+
 /* ===========================================================================
   Opens a gzip (.gz) file for reading or writing. The mode parameter
   is as in fopen ("rb" or "wb"). The file is given either by file descriptor
@@ -52,8 +86,8 @@ int az_open (azio_stream *s, const char *path, int Flags, File fd)
   int level = Z_DEFAULT_COMPRESSION; /* compression level */
   int strategy = Z_DEFAULT_STRATEGY; /* compression strategy */
 
-  s->stream.zalloc = (alloc_func)0;
-  s->stream.zfree = (free_func)0;
+  s->stream.zalloc = az_allocator;
+  s->stream.zfree = az_free;
   s->stream.opaque = (voidpf)0;
   memset(s->inbuf, 0, AZ_BUFSIZE_READ);
   memset(s->outbuf, 0, AZ_BUFSIZE_WRITE);