[clang-format] Fix repeated backslash insertion in macro line comments

Line comments in preprocessor directives were incorrectly marked as
continuing the directive, causing clang-format to add backslashes
after them on repeated runs. Backslashes appended after line comments in
this way do not continue the PP directive because the following line
would also become part of the comment.

Fix by unsetting InPPDirective in WhitespaceManager::replaceWhitespace
for line comments in two places: when breaking lines and when formatting
tokens on the same line. This stops the spurious backslash insertion for
both standalone line comments after PP directives and trailing line
comments after macro bodies.

Fixes #164282.

Co-authored-by: Björn Schäpers <[email protected]>
Signed-off-by: Ruoyu Zhong <[email protected]>

Author: ZhongRuoyu

clang/lib/Format/ContinuationIndenter.cpp

@@ -798,9 +798,11 @@ void ContinuationIndenter::addTokenOnCurrentLine(LineState &State, bool DryRun,
   }
 
   if (!DryRun) {
+    const bool ContinuePPDirective =
+        State.Line->InMacroBody && Current.isNot(TT_LineComment);
     Whitespaces.replaceWhitespace(Current, /*Newlines=*/0, Spaces,
                                   State.Column + Spaces + PPColumnCorrection,
-                                  /*IsAligned=*/false, State.Line->InMacroBody);
+                                  /*IsAligned=*/false, ContinuePPDirective);
   }
 
   // If "BreakBeforeInheritanceComma" mode, don't break within the inheritance
@@ -1176,10 +1178,11 @@ unsigned ContinuationIndenter::addTokenOnNewLine(LineState &State,
       // about removing empty lines on closing blocks. Special case them here.
       MaxEmptyLinesToKeep = 1;
     }
-    unsigned Newlines =
+    const unsigned Newlines =
         std::max(1u, std::min(Current.NewlinesBefore, MaxEmptyLinesToKeep));
-    bool ContinuePPDirective =
-        State.Line->InPPDirective && State.Line->Type != LT_ImportStatement;
+    const bool ContinuePPDirective = State.Line->InPPDirective &&
+                                     State.Line->Type != LT_ImportStatement &&
+                                     Current.isNot(TT_LineComment);
     Whitespaces.replaceWhitespace(Current, Newlines, State.Column, State.Column,
                                   CurrentState.IsAligned, ContinuePPDirective);
   }

clang/unittests/Format/FormatTestComments.cpp

@@ -839,6 +839,25 @@ TEST_F(FormatTestComments, MultiLineCommentsInDefines) {
                    getLLVMStyleWithColumns(17)));
 }
 
+TEST_F(FormatTestComments, LineCommentsInMacrosDoNotGetEscapedNewlines) {
+  FormatStyle Style = getLLVMStyleWithColumns(0);
+  Style.ReflowComments = FormatStyle::RCS_Never;
+  verifyFormat("#define FOO (1U) // comment\n"
+               "                 // comment",
+               Style);
+
+  Style.ColumnLimit = 32;
+  verifyFormat("#define SOME_MACRO(x) x\n"
+               "#define FOO                    \\\n"
+               "  SOME_MACRO(1) +              \\\n"
+               "      SOME_MACRO(2) // comment\n"
+               "                    // comment",
+               "#define SOME_MACRO(x) x\n"
+               "#define FOO SOME_MACRO(1) + SOME_MACRO(2) // comment\n"
+               "                                          // comment",
+               Style);
+}
+
 TEST_F(FormatTestComments, ParsesCommentsAdjacentToPPDirectives) {
   EXPECT_EQ("namespace {}\n// Test\n#define A",
             format("namespace {}\n   // Test\n#define A"));