[clang] [clang-format] Identify include guard #endif followed by comments (PR #186848)

[via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/186848

Fixes #176321

>From 6b6db2ce365120aabdc9a2063a3f12ecfa7feac4 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Mon, 16 Mar 2026 10:48:07 -0700
Subject: [PATCH] [clang-format] Identify include guard #endif followed by
 comments

Fixes #176321
---
 clang/lib/Format/UnwrappedLineParser.cpp | 16 ++++++++++------
 clang/unittests/Format/FormatTest.cpp    |  7 +++++++
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 9cefe9408f0ab..08c962dd34bbb 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1147,12 +1147,6 @@ void UnwrappedLineParser::parsePPElse() {
 void UnwrappedLineParser::parsePPEndIf() {
   conditionalCompilationEnd();
   parsePPUnknown();
-  // If the #endif of a potential include guard is the last thing in the file,
-  // then we found an include guard.
-  if (IncludeGuard == IG_Defined && PPBranchLevel == -1 && Tokens->isEOF() &&
-      getIncludeGuardState(Style.IndentPPDirectives) == IG_Inited) {
-    IncludeGuard = IG_Found;
-  }
 }
 
 void UnwrappedLineParser::parsePPDefine() {
@@ -4952,10 +4946,20 @@ void UnwrappedLineParser::readToken(int LevelDifference) {
       assert(Line->Level >= Line->UnbracedBodyLevel);
       Line->Level -= Line->UnbracedBodyLevel;
       flushComments(isOnNewLine(*FormatTok));
+      const bool IsEndIf = Tokens->peekNextToken()->is(tok::pp_endif);
       parsePPDirective();
       PreviousWasComment = FormatTok->is(tok::comment);
       FirstNonCommentOnLine = IsFirstNonCommentOnLine(
           FirstNonCommentOnLine, *FormatTok, PreviousWasComment);
+      // If the #endif of a potential include guard is the last thing in the
+      // file, then we found an include guard.
+      if (IsEndIf && IncludeGuard == IG_Defined && PPBranchLevel == -1 &&
+          getIncludeGuardState(Style.IndentPPDirectives) == IG_Inited &&
+          (eof() ||
+           (PreviousWasComment &&
+            Tokens->peekNextToken(/*SkipComment=*/true)->is(tok::eof)))) {
+        IncludeGuard = IG_Found;
+      }
     }
 
     if (!PPStack.empty() && (PPStack.back().Kind == PP_Unreachable) &&
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 56985abf12559..77676184f0d6a 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -6701,6 +6701,13 @@ TEST_F(FormatTest, IndentPreprocessorDirectives) {
                "\n"
                "#define FGHIJK",
                Style);
+
+  verifyFormat("#ifndef FOO_H\n"
+               "#define FOO_H\n"
+               "#include <iostream>\n"
+               "#endif\n"
+               "// comment",
+               Style);
 }
 
 TEST_F(FormatTest, FormatAlignInsidePreprocessorElseBlock) {