[clang-tools-extra] [clang-tidy] Replace /* ... */ single-line comments with // ... comments (PR #124319)

[Congcong Cai via cfe-commits]

================
@@ -0,0 +1,127 @@
+//===--- UseCppStyleCommentsCheck.cpp - clang-tidy-------------------------===//
+
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseCppStyleCommentsCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Lex/Preprocessor.h"
+#include <iostream>
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::modernize {
+class UseCppStyleCommentsCheck::CStyleCommentHandler : public CommentHandler {
+public:
+  CStyleCommentHandler(UseCppStyleCommentsCheck &Check)
+      : Check(Check),
+        CStyleCommentMatch(
+            "^[ \t]*/\\*+[ \t\r\n]*(.*[ \t\r\n]*)*[ \t\r\n]*\\*+/[ \t\r\n]*$") {
+  }
+
+  std::string convertToCppStyleComment(const SourceManager &SM,
+                                       const SourceRange &Range) {
+    StringRef CommentText = Lexer::getSourceText(
+        CharSourceRange::getTokenRange(Range), SM, LangOptions());
+
+    std::string InnerText = CommentText.str();
+    InnerText.erase(0, 2);
+    InnerText.erase(InnerText.size() - 2, 2);
+
+    std::string Result;
+    std::istringstream Stream(InnerText);
+    std::string Line;
+
+    if (std::getline(Stream, Line)) {
+      size_t startPos = Line.find_first_not_of(" \t");
+      if (startPos != std::string::npos) {
+        Line = Line.substr(startPos);
+      } else {
+        Line.clear();
+      }
+      Result += "// " + Line;
+    }
+
+    while (std::getline(Stream, Line)) {
+      size_t startPos = Line.find_first_not_of(" \t");
+      if (startPos != std::string::npos) {
+        Line = Line.substr(startPos);
+      } else {
+        Line.clear();
+      }
+      Result += "\n// " + Line;
+    }
+    return Result;
+  }
+
+  bool HandleComment(Preprocessor &PP, SourceRange Range) override {
+    const SourceManager &SM = PP.getSourceManager();
+
+    if (Range.getBegin().isMacroID() || SM.isInSystemHeader(Range.getBegin())) {
+      return false;
+    }
+
+    const StringRef Text = Lexer::getSourceText(
+        CharSourceRange::getCharRange(Range), SM, PP.getLangOpts());
+
+    SmallVector<StringRef> Matches;
+    if (!CStyleCommentMatch.match(Text, &Matches)) {
+      return false;
+    }
+
+    SourceLocation CommentStart = Range.getBegin();
+    SourceLocation CommentEnd = Range.getEnd();
+
+    unsigned StartLine = SM.getSpellingLineNumber(CommentStart);
+    unsigned EndLine = SM.getSpellingLineNumber(CommentEnd);
+
+    if (StartLine == EndLine) {
+      SourceLocation LineBegin =
+          SM.translateLineCol(SM.getFileID(CommentStart), StartLine, 1);
+      SourceLocation LineEnd =
+          SM.translateLineCol(SM.getFileID(CommentEnd), EndLine,
+                              std::numeric_limits<unsigned>::max());
+      StringRef LineContent = Lexer::getSourceText(
+          CharSourceRange::getCharRange(LineBegin, LineEnd), SM,
+          PP.getLangOpts());
+      size_t CommentStartOffset = SM.getSpellingColumnNumber(CommentStart) - 1;
+      StringRef AfterComment =
+          LineContent.drop_front(CommentStartOffset + Text.size());
+
+      if (!AfterComment.trim().empty()) {
+        return false;
+      }
+    }
+
+    Check.diag(
----------------
HerrCai0907 wrote:

could you add test like

```c++
/* aaa 
    bbbb
    ccc */ int a = 1;
```

It may not be processed correctly.

https://github.com/llvm/llvm-project/pull/124319