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

returned empty string.

Misc/NEWS

@@ -12,6 +12,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #3015: Fixed tkinter with wantobject=False.  Any Tcl command call
+  returned empty string.
+
 - Issue #19037: The mailbox module now makes all changes to maildir files
   before moving them into place, to avoid race conditions with other programs
   that may be accessing the maildir directory.

Modules/_tkinter.c

@@ -1107,10 +1107,7 @@ 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;
 }