Fix assertion in BreakableBlockComment (http://llvm.org/PR21916).

Reviewers: djasper

Reviewed By: djasper

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D6894

llvm-svn: 225628

2 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/Format/BreakableToken.cpp b/clang/lib/Format/BreakableToken.cpp
index 1bea0e56513..26f1371b409 100644
--- a/clang/lib/Format/BreakableToken.cpp
+++ b/clang/lib/Format/BreakableToken.cpp
@@ -303,7 +303,8 @@ BreakableBlockComment::BreakableBlockComment(
     StartOfLineColumn[i] += Decoration.size();
     Lines[i] = Lines[i].substr(Decoration.size());
     LeadingWhitespace[i] += Decoration.size();
-    IndentAtLineBreak = std::min<int>(IndentAtLineBreak, StartOfLineColumn[i]);
+    IndentAtLineBreak =
+        std::min<int>(IndentAtLineBreak, std::max(0, StartOfLineColumn[i]));
   }
   IndentAtLineBreak = std::max<unsigned>(IndentAtLineBreak, Decoration.size());
   DEBUG({
diff --git a/clang/lib/Format/BreakableToken.h b/clang/lib/Format/BreakableToken.h
index 6f49ed2d367..eb1f9fda307 100644
--- a/clang/lib/Format/BreakableToken.h
+++ b/clang/lib/Format/BreakableToken.h
@@ -212,6 +212,11 @@ private:
   // StartOfLineColumn[i] is the target column at which Line[i] should be.
   // Note that this excludes a leading "* " or "*" in case all lines have
   // a "*" prefix.
+  // The first line's target column is always positive. The remaining lines'
+  // target columns are relative to the first line to allow correct indentation
+  // of comments in \c WhitespaceManager. Thus they can be negative as well (in
+  // case the first line needs to be unindented more than there's actual
+  // whitespace in another line).
   SmallVector<int, 16> StartOfLineColumn;
 
   // The column at which the text of a broken line should start.