Issue #3015: Fixed tkinter with wantobject=False. Any Tcl command call

returned empty string.

Misc/NEWS

@@ -68,6 +68,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #3015: Fixed tkinter with wantobject=False.  Any Tcl command call
+  returned empty string.
+
 - Issue #18050: Fixed an incompatibility of the re module with Python 3.3.0
   binaries.
 

Modules/_tkinter.c

@@ -1227,10 +1227,7 @@ Tkapp_CallResult(TkappObject *self)
         res = FromObj((PyObject*)self, value);
         Tcl_DecrRefCount(value);
     } else {
-        const char *s = Tcl_GetStringResult(self->interp);
-        const char *p = s;
-
-        res = PyUnicode_FromStringAndSize(s, (int)(p-s));
+        res = PyUnicode_FromString(Tcl_GetStringResult(self->interp));
     }
     return res;
 }