1 files changed, 56 insertions, 0 deletions
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 1b35c56..493378c 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -434,6 +434,7 @@ Tcl_GetCharLength(
 	return length;
     }
 
+
     /*
      * OK, need to work with the object as a string.
      */
@@ -464,6 +465,50 @@ Tcl_GetCharLength(
     }
     return numChars;
 }
+
+
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclCheckEmptyString --
+ *
+ *	Determine whether the string value of an object is or would be the
+ *	empty string, without generating a string representation.
+ *
+ * Results:
+ *	Returns 1 if empty, 0 if not, and -1 if unknown.
+ *
+ * Side effects:
+ *	None.
+ *
+ *----------------------------------------------------------------------
+ */
+int
+TclCheckEmptyString (
+    Tcl_Obj *objPtr
+) {
+    int length = -1;
+
+    if (objPtr->bytes == tclEmptyStringRep) {
+	return TCL_EMPTYSTRING_YES;
+    }
+
+    if (TclIsPureList(objPtr)) {
+	Tcl_ListObjLength(NULL, objPtr, &length);
+	return length == 0;
+    }
+
+    if (TclIsPureDict(objPtr)) {
+	Tcl_DictObjSize(NULL, objPtr, &length);
+	return length == 0;
+    }
+    
+    if (objPtr->bytes == NULL) {
+	return TCL_EMPTYSTRING_UNKNOWN;
+    }
+    return objPtr->length == 0;
+}
 
 /*
  *----------------------------------------------------------------------
@@ -1831,6 +1876,11 @@ Tcl_AppendFormatToObj(
 	width = 0;
 	if (isdigit(UCHAR(ch))) {
 	    width = strtoul(format, &end, 10);
+	    if (width < 0) {
+		msg = overflow;
+		errCode = "OVERFLOW";
+		goto errorMsg;
+	    }
 	    format = end;
 	    step = TclUtfToUniChar(format, &ch);
 	} else if (ch == '*') {
@@ -1951,6 +2001,12 @@ Tcl_AppendFormatToObj(
 		goto error;
 	    }
 	    length = Tcl_UniCharToUtf(code, buf);
+#if TCL_UTF_MAX > 3
+	    if (!length) {
+		/* Special case for handling upper surrogates. */
+		length = Tcl_UniCharToUtf(-1, buf);
+	    }
+#endif
 	    segment = Tcl_NewStringObj(buf, length);
 	    Tcl_IncrRefCount(segment);
 	    allocSegment = 1;