[clang-format] Emit absolute splits before lines for comments

Summary:
This patch makes the splits emitted for the beginning of comment lines during
reformatting absolute. Previously, they were relative to the start of the
non-whitespace content of the line, which messes up further TailOffset
calculations in breakProtrudingToken. This fixes an assertion failure reported
in bug 34236: https://bugs.llvm.org/show_bug.cgi?id=34236.

Reviewers: djasper

Reviewed By: djasper

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D36956

llvm-svn: 311559

1 files changed, 17 insertions, 0 deletions

diff --git a/clang/unittests/Format/FormatTestComments.cpp b/clang/unittests/Format/FormatTestComments.cpp
index 79dc003ae85..70fa965adee 100644
--- a/clang/unittests/Format/FormatTestComments.cpp
+++ b/clang/unittests/Format/FormatTestComments.cpp
@@ -2803,6 +2803,23 @@ TEST_F(FormatTestComments, NonTrailingBlockComments) {
                    "    A = B;",
                    getLLVMStyleWithColumns(40)));
 }
+
+TEST_F(FormatTestComments, NoCrush_Bug34236) {
+  // This is a test case from a crasher reported in:
+  // https://bugs.llvm.org/show_bug.cgi?id=34236
+  EXPECT_EQ(
+      R"(
+/*                                                                */ /*
+                                                                      *       a
+                                                                      * b c
+                                                                      * d*/)",
+      format(
+          R"(
+/*                                                                */ /*
+ *       a b
+ *       c     d*/)",
+          getLLVMStyleWithColumns(80)));
+}
 } // end namespace
 } // end namespace format
 } // end namespace clang