[clang] 5978842 - Fix clang-format bug when handling conflict markers.

[Manuel Klimek via cfe-commits]

Author: Manuel Klimek
Date: 2021-12-01T11:23:04+01:00
New Revision: 59788422609433c50c3d3c16ca531fa56b9acb4f

URL: https://github.com/llvm/llvm-project/commit/59788422609433c50c3d3c16ca531fa56b9acb4f
DIFF: https://github.com/llvm/llvm-project/commit/59788422609433c50c3d3c16ca531fa56b9acb4f.diff

LOG: Fix clang-format bug when handling conflict markers.

Previously, clang-format would not correctly identify preprocessor
directives directly following a conflict marker, which would result in
violating the formatter's invariants.

The provided test fails in assert mode before this change.

Added: 
    

Modified: 
    clang/lib/Format/UnwrappedLineParser.cpp
    clang/unittests/Format/FormatTest.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index da35648ef1ca0..a7e0422e3146c 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -3388,6 +3388,20 @@ void UnwrappedLineParser::readToken(int LevelDifference) {
   do {
     FormatTok = Tokens->getNextToken();
     assert(FormatTok);
+    while (FormatTok->getType() == TT_ConflictStart ||
+           FormatTok->getType() == TT_ConflictEnd ||
+           FormatTok->getType() == TT_ConflictAlternative) {
+      if (FormatTok->getType() == TT_ConflictStart) {
+        conditionalCompilationStart(/*Unreachable=*/false);
+      } else if (FormatTok->getType() == TT_ConflictAlternative) {
+        conditionalCompilationAlternative();
+      } else if (FormatTok->getType() == TT_ConflictEnd) {
+        conditionalCompilationEnd();
+      }
+      FormatTok = Tokens->getNextToken();
+      FormatTok->MustBreakBefore = true;
+    }
+
     while (!Line->InPPDirective && FormatTok->Tok.is(tok::hash) &&
            (FormatTok->HasUnescapedNewline || FormatTok->IsFirst)) {
       distributeComments(Comments, FormatTok);
@@ -3409,19 +3423,6 @@ void UnwrappedLineParser::readToken(int LevelDifference) {
       flushComments(isOnNewLine(*FormatTok));
       parsePPDirective();
     }
-    while (FormatTok->getType() == TT_ConflictStart ||
-           FormatTok->getType() == TT_ConflictEnd ||
-           FormatTok->getType() == TT_ConflictAlternative) {
-      if (FormatTok->getType() == TT_ConflictStart) {
-        conditionalCompilationStart(/*Unreachable=*/false);
-      } else if (FormatTok->getType() == TT_ConflictAlternative) {
-        conditionalCompilationAlternative();
-      } else if (FormatTok->getType() == TT_ConflictEnd) {
-        conditionalCompilationEnd();
-      }
-      FormatTok = Tokens->getNextToken();
-      FormatTok->MustBreakBefore = true;
-    }
 
     if (!PPStack.empty() && (PPStack.back().Kind == PP_Unreachable) &&
         !Line->InPPDirective) {

diff  --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 39f1b835fb766..65809ab5e7579 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -21117,6 +21117,14 @@ TEST_F(FormatTest, HandleConflictMarkers) {
                    ">>>>>>>\n"
                    "  End\n"
                    "int i;\n"));
+
+  verifyFormat(R"(====
+#ifdef A
+a
+#else
+b
+#endif
+)");
 }
 
 TEST_F(FormatTest, DisableRegions) {