Index: lldb/bindings/interface/SBThread.i
===================================================================
--- lldb/bindings/interface/SBThread.i
+++ lldb/bindings/interface/SBThread.i
@@ -127,7 +127,7 @@
     Pass only an (int)length and expect to get a Python string describing the
     stop reason.") GetStopDescription;
     size_t
-    GetStopDescription (char *dst, size_t dst_len);
+    GetStopDescription (char *dst_or_null, size_t dst_len);
 
     SBValue
     GetStopReturnValue ();
Index: lldb/bindings/python/python-typemaps.swig
===================================================================
--- lldb/bindings/python/python-typemaps.swig
+++ lldb/bindings/python/python-typemaps.swig
@@ -95,7 +95,6 @@
 /* Typemap definitions to allow SWIG to properly handle char buffer. */
 
 // typemap for a char buffer
-// See also SBThread::GetStopDescription.
 %typemap(in) (char *dst, size_t dst_len) {
    if (!PyInt_Check($input)) {
        PyErr_SetString(PyExc_ValueError, "Expecting an integer");
@@ -113,7 +112,6 @@
 %typemap(in) (void *char_buf, size_t size) = (char *dst, size_t dst_len);
 
 // Return the char buffer.  Discarding any previous return result
-// See also SBThread::GetStopDescription.
 %typemap(argout) (char *dst, size_t dst_len) {
    Py_XDECREF($result);   /* Blow away any previous result */
    if (result == 0) {
@@ -132,6 +130,28 @@
 %typemap(argout) (void *char_buf, size_t size) = (char *dst, size_t dst_len);
 
 
+// typemap for handling an snprintf-like API like SBThread::GetStopDescription.
+%typemap(in) (char *dst_or_null, size_t dst_len) {
+   if (!PyInt_Check($input)) {
+       PyErr_SetString(PyExc_ValueError, "Expecting an integer");
+       return NULL;
+   }
+   $2 = PyInt_AsLong($input);
+   if ($2 <= 0) {
+       PyErr_SetString(PyExc_ValueError, "Positive integer expected");
+       return NULL;
+   }
+   $1 = (char *) malloc($2);
+}
+%typemap(argout) (char *dst_or_null, size_t dst_len) {
+   Py_XDECREF($result);   /* Blow away any previous result */
+   llvm::StringRef ref($1);
+   PythonString string(ref);
+   $result = string.release();
+   free($1);
+}
+
+
 // typemap for an outgoing buffer
 // See also SBEvent::SBEvent(uint32_t event, const char *cstr, uint32_t cstr_len).
 // Ditto for SBProcess::PutSTDIN(const char *src, size_t src_len).
Index: lldb/packages/Python/lldbsuite/test/python_api/thread/TestThreadAPI.py
===================================================================
--- lldb/packages/Python/lldbsuite/test/python_api/thread/TestThreadAPI.py
+++ lldb/packages/Python/lldbsuite/test/python_api/thread/TestThreadAPI.py
@@ -122,14 +122,20 @@
         self.assertTrue(
             thread.IsValid(),
             "There should be a thread stopped due to breakpoint")
-        #self.runCmd("process status")
-
-        # Due to the typemap magic (see lldb.swig), we pass in an (int)length to GetStopDescription
-        # and expect to get a Python string as the return object!
-        # The 100 is just an arbitrary number specifying the buffer size.
-        stop_description = thread.GetStopDescription(100)
-        self.expect(stop_description, exe=False,
-                    startstr='breakpoint')
+
+        # Get the stop reason. GetStopDescription expects that we pass in the size of the description
+        # we expect plus an additional byte for the null terminator.
+
+        # Test with a buffer that is exactly as large as the expected stop reason.
+        self.assertEqual("breakpoint 1.1", thread.GetStopDescription(len('breakpoint 1.1') + 1))
+
+        # Test some smaller buffer sizes.
+        self.assertEqual("breakpoint", thread.GetStopDescription(len('breakpoint') + 1))
+        self.assertEqual("break", thread.GetStopDescription(len('break') + 1))
+        self.assertEqual("b", thread.GetStopDescription(len('b') + 1))
+
+        # Test that we can pass in a much larger size and still get the right output.
+        self.assertEqual("breakpoint 1.1", thread.GetStopDescription(len('breakpoint 1.1') + 100))
 
     def step_out_of_malloc_into_function_b(self, exe_name):
         """Test Python SBThread.StepOut() API to step out of a malloc call where the call site is at function b()."""