[clang-tools-extra] [llvm] New check `misc-header-guard` (PR #177315)

[Yanzuo Liu via llvm-commits]

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@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "HeaderGuardCheck.h"
+#include "../utils/OptionsUtils.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/Path.h"
+
+namespace clang::tidy::misc {
+
+HeaderGuardCheck::HeaderGuardCheck(StringRef Name, ClangTidyContext *Context)
+    : clang::tidy::utils::HeaderGuardCheck(Name, Context),
+      HeaderDirs(utils::options::parseStringList(
+          Options.get("HeaderDirs", "include"))),
+      Prefix(Options.get("Prefix", "")) {}
+
+std::string HeaderGuardCheck::getHeaderGuard(StringRef Filename,
+                                             StringRef OldGuard) {
+  std::string Guard = tooling::getAbsolutePath(Filename);
+
+  // When running under Windows, need to convert the path separators from
+  // `\` to `/`.
+  Guard = llvm::sys::path::convert_to_slash(Guard);
+
+  // consider all directories from HeaderDirs option. Stop at first found.
+  for (const StringRef HeaderDir : HeaderDirs) {
+    const size_t PosHeaderDir = Guard.rfind(HeaderDir.str() + "/");
----------------
zwuis wrote:

It seems that we should add `/` before `HeaderDir`.

```cpp
"/" + HeaderDir.str() + "/"
```

https://github.com/llvm/llvm-project/pull/177315