1 files changed, 33 insertions, 13 deletions

diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 04cf4ee..dffa38c 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -140,9 +140,9 @@ typedef struct String {
 #define stringAttemptRealloc(ptr, numChars) \
     (String *) attemptckrealloc((ptr), (unsigned) STRING_SIZE(numChars) )
 #define GET_STRING(objPtr) \
-	((String *) (objPtr)->internalRep.otherValuePtr)
+	((String *) (objPtr)->internalRep.twoPtrValue.ptr1)
 #define SET_STRING(objPtr, stringPtr) \
-	((objPtr)->internalRep.otherValuePtr = (void *) (stringPtr))
+	((objPtr)->internalRep.twoPtrValue.ptr1 = (void *) (stringPtr))
 
 /*
  * TCL STRING GROWTH ALGORITHM
@@ -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;
     }