[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. Line comments cannot span multiple lines
with backslashes, so they should not be treated as PP directive
continuations.

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 preprocessor directives and trailing
line comments after macro bodies.

Fixes #164282.

Author: ZhongRuoyu

clang/lib/Format/ContinuationIndenter.cpp

@@ -798,9 +798,11 @@ void ContinuationIndenter::addTokenOnCurrentLine(LineState &State, bool DryRun,
   }
 
   if (!DryRun) {
+    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
@@ -1178,8 +1180,9 @@ unsigned ContinuationIndenter::addTokenOnNewLine(LineState &State,
     }
     unsigned Newlines =
         std::max(1u, std::min(Current.NewlinesBefore, MaxEmptyLinesToKeep));
-    bool ContinuePPDirective =
-        State.Line->InPPDirective && State.Line->Type != LT_ImportStatement;
+    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;
+  EXPECT_EQ("#define SOME_MACRO(x) x\n"
+            "#define FOO                    \\\n"
+            "  SOME_MACRO(1) +              \\\n"
+            "      SOME_MACRO(2) // comment\n"
+            "                    // comment",
+            format("#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"));