(Tcl_SetByteArrayObj): Only zero out the memory block if it is not being

immediately overwritten. Thanks to Stuart Cassoff for spotting.

2 files changed, 13 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index b180bcd..987a251 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,12 @@
+2012-03-02  Donal K. Fellows  <dkf@users.sf.net>
+
+	* generic/tclBinary.c (Tcl_SetByteArrayObj): Only zero out the memory
+	block if it is not being immediately overwritten. (Caller might still
+	overwrite, but we should at least avoid known-useless work.)
+
 2012-02-29  Jan Nijtmans  <nijtmans@users.sf.net>
 
-	* generic/tclIOUtil.c:	[Bug 3466099] BOM in Unicode
+	* generic/tclIOUtil.c:	[Bug 3466099]: BOM in Unicode
 	* generic/tclEncoding.c:
 	* tests/source.test
 
diff --git a/generic/tclBinary.c b/generic/tclBinary.c
index 0a340f2..444e7fa 100644
--- a/generic/tclBinary.c
+++ b/generic/tclBinary.c
@@ -305,11 +305,14 @@ Tcl_SetByteArrayObj(
 
     length = (length < 0) ? 0 : length;
     byteArrayPtr = ckalloc(BYTEARRAY_SIZE(length));
-    memset(byteArrayPtr, 0, BYTEARRAY_SIZE(length));
     byteArrayPtr->used = length;
     byteArrayPtr->allocated = length;
-    if (bytes && length) {
-	memcpy(byteArrayPtr->bytes, bytes, (size_t) length);
+    if (length) {
+	if (bytes) {
+	    memcpy(byteArrayPtr->bytes, bytes, (size_t) length);
+	} else {
+	    memset(byteArrayPtr->bytes, 0, (size_t) length);
+	}
     }
 
     objPtr->typePtr = &tclByteArrayType;