[clang-tools-extra] [clang-tidy] warn when `true` is used as a preprocessor keyword in C (PR #128265)

[via cfe-commits]

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@@ -0,0 +1,123 @@
+//===--- TrueMacroCheck.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 "TrueMacroCheck.h"
+#include "clang/Lex/MacroInfo.h"
+#include "clang/Lex/PPCallbacks.h"
+#include "clang/Lex/Preprocessor.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+namespace {
+
+class MacroCallback : public PPCallbacks {
+  static constexpr const char *TrueMacroSpelling = "true";
+
+public:
+  MacroCallback(TrueMacroCheck *Check, Preprocessor *PP)
+      : Check(Check), PP(PP) {}
+  void MacroDefined(const Token &MacroNameTok,
+                    const MacroDirective *MD) override {
+    if (TrueDefined)
+      return;
+
+    const MacroInfo *MI = MD->getMacroInfo();
+    for (const Token &Tok : MI->tokens()) {
+      if (PP->getSpelling(Tok) == TrueMacroSpelling)
+        emitDiagnostics(Tok.getLocation(),
+                        {Tok.getLocation(), Tok.getEndLoc()});
+    }
+
+    if (PP->getSpelling(MacroNameTok) == TrueMacroSpelling)
+      TrueDefined = true;
+  }
+
+  virtual void MacroUndefined(const Token &MacroNameTok,
+                              const MacroDefinition &MD,
+                              const MacroDirective *Undef) override {
+    if (PP->getSpelling(MacroNameTok) == TrueMacroSpelling)
+      TrueDefined = false;
+  }
+
+  virtual void If(SourceLocation Loc, SourceRange ConditionRange,
+                  ConditionValueKind ConditionValue) override {
+    StringRef Condition =
----------------
EugeneZelenko wrote:

```suggestion
    const StringRef Condition =
```

https://github.com/llvm/llvm-project/pull/128265