Index: cfe/trunk/lib/Format/TokenAnnotator.cpp
===================================================================
--- cfe/trunk/lib/Format/TokenAnnotator.cpp
+++ cfe/trunk/lib/Format/TokenAnnotator.cpp
@@ -1099,6 +1099,8 @@
 
 public:
   LineType parseLine() {
+    if (!CurrentToken)
+      return LT_Invalid;
     NonTemplateLess.clear();
     if (CurrentToken->is(tok::hash))
       return parsePreprocessorDirective();
Index: cfe/trunk/unittests/Format/FormatTest.cpp
===================================================================
--- cfe/trunk/unittests/Format/FormatTest.cpp
+++ cfe/trunk/unittests/Format/FormatTest.cpp
@@ -3087,6 +3087,15 @@
                "#endif\n"
                "#endif\n",
                Style);
+  // Don't crash if there is an #elif directive without a condition.
+  verifyFormat("#if 1\n"
+               "int x;\n"
+               "#elif\n"
+               "int y;\n"
+               "#else\n"
+               "int z;\n"
+               "#endif",
+               Style);
   // FIXME: This doesn't handle the case where there's code between the
   // #ifndef and #define but all other conditions hold. This is because when
   // the #define line is parsed, UnwrappedLineParser::Lines doesn't hold the