Fix crash on unmatched #endif's.

The following snippet would crash:
  #endif
  #if A

llvm-svn: 200381

2 files changed, 8 insertions, 1 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index dbd8d9dbc1b..b56140e763d 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -509,7 +509,9 @@ void UnwrappedLineParser::parsePPEndIf() {
       PPLevelBranchCount[PPBranchLevel] = PPChainBranchIndex.top() + 1;
     }
   }
-  --PPBranchLevel;
+  // Guard against #endif's without #if.
+  if (PPBranchLevel > 0)
+    --PPBranchLevel;
   if (!PPChainBranchIndex.empty())
     PPChainBranchIndex.pop();
   if (!PPStack.empty())
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index efc563b4f25..9b0a11c3bc2 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -2427,6 +2427,11 @@ TEST_F(FormatTest, LayoutStatementsAroundPreprocessorDirectives) {
                "#endif");
 }
 
+TEST_F(FormatTest, GraciouslyHandleIncorrectPreprocessorConditions) {
+  verifyFormat("#endif\n"
+               "#if B");
+}
+
 TEST_F(FormatTest, FormatsJoinedLinesOnSubsequentRuns) {
   FormatStyle SingleLine = getLLVMStyle();
   SingleLine.AllowShortIfStatementsOnASingleLine = true;