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-rw-r--r--generic/tclStringObj.c42
1 files changed, 31 insertions, 11 deletions
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index e495c2e..dffa38c 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -1281,23 +1281,43 @@ Tcl_AppendObjToObj(
if ((TclIsPureByteArray(objPtr) || objPtr->bytes == tclEmptyStringRep)
&& TclIsPureByteArray(appendObjPtr)) {
- unsigned char *bytesSrc;
- int lengthSrc, lengthTotal;
/*
- * We do not assume that objPtr and appendObjPtr must be distinct!
- * This makes this code a bit more complex than it otherwise would be,
- * but in turn makes it much safer.
+ * You might expect the code here to be
+ *
+ * bytes = Tcl_GetByteArrayFromObj(appendObjPtr, &length);
+ * TclAppendBytesToByteArray(objPtr, bytes, length);
+ *
+ * and essentially all of the time that would be fine. However,
+ * it would run into trouble in the case where objPtr and
+ * appendObjPtr point to the same thing. That may never be a
+ * good idea. It seems to violate Copy On Write, and we don't
+ * have any tests for the situation, since making any Tcl commands
+ * that call Tcl_AppendObjToObj() do that appears impossible
+ * (They honor Copy On Write!). For the sake of extensions that
+ * go off into that realm, though, here's a more complex approach
+ * that can handle all the cases.
*/
+ /* Get lengths */
+ int lengthSrc;
+
(void) Tcl_GetByteArrayFromObj(objPtr, &length);
(void) Tcl_GetByteArrayFromObj(appendObjPtr, &lengthSrc);
- lengthTotal = length + lengthSrc;
- if (((length > lengthSrc) ? length : lengthSrc) > lengthTotal) {
- Tcl_Panic("max size for a Tcl value (%d bytes) exceeded", INT_MAX);
- }
- bytesSrc = Tcl_GetByteArrayFromObj(appendObjPtr, NULL);
- TclAppendBytesToByteArray(objPtr, bytesSrc, lengthSrc);
+
+ /* Grow buffer enough for the append */
+ TclAppendBytesToByteArray(objPtr, NULL, lengthSrc);
+
+ /* Reset objPtr back to the original value */
+ Tcl_SetByteArrayLength(objPtr, length);
+
+ /*
+ * Now do the append knowing that buffer growth cannot cause
+ * any trouble.
+ */
+
+ TclAppendBytesToByteArray(objPtr,
+ Tcl_GetByteArrayFromObj(appendObjPtr, NULL), lengthSrc);
return;
}