[clang-tools-extra] [clang-tidy] new check readability-mark-static (PR #90830)

[Danny Mösch via cfe-commits]

================
@@ -0,0 +1,80 @@
+//===--- UnnecessaryExternalLinkageCheck.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 "UnnecessaryExternalLinkageCheck.h"
+#include "clang/AST/Decl.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/Basic/Specifiers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+
+AST_POLYMORPHIC_MATCHER(isFirstDecl,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(FunctionDecl,
+                                                        VarDecl)) {
+  return Node.isFirstDecl();
+}
+
+AST_MATCHER(Decl, isInMainFile) {
+  for (const Decl *D : Node.redecls())
+    if (!Finder->getASTContext().getSourceManager().isInMainFile(
+            D->getLocation()))
+      return false;
+  return true;
+}
+
+AST_POLYMORPHIC_MATCHER(isExternStorageClass,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES(FunctionDecl,
+                                                        VarDecl)) {
+  return Node.getStorageClass() == SC_Extern;
+}
+
+} // namespace
+
+void UnnecessaryExternalLinkageCheck::registerMatchers(MatchFinder *Finder) {
+  auto Common = allOf(isFirstDecl(), isInMainFile(),
+                      unless(anyOf(
+                          // 1. internal linkage
+                          isStaticStorageClass(), isInAnonymousNamespace(),
+                          // 2. explicit external linkage
+                          isExternStorageClass(), isExternC(),
+                          // 3. template
+                          isExplicitTemplateSpecialization(),
+                          clang::ast_matchers::isTemplateInstantiation(),
+                          // 4. friend
+                          hasAncestor(friendDecl()))));
+  Finder->addMatcher(
+      functionDecl(Common, unless(cxxMethodDecl()), unless(isMain()))
+          .bind("fn"),
+      this);
+  Finder->addMatcher(varDecl(Common, hasGlobalStorage()).bind("var"), this);
+}
+
+static constexpr StringRef Message =
+    "%0 %1 can be internal linkage, "
+    "marking as static or using anonymous namespace can avoid external "
+    "linkage.";
+
+void UnnecessaryExternalLinkageCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *FD = Result.Nodes.getNodeAs<FunctionDecl>("fn")) {
+    diag(FD->getLocation(), Message) << "function" << FD;
+    return;
+  }
+  if (const auto *VD = Result.Nodes.getNodeAs<VarDecl>("var")) {
+    diag(VD->getLocation(), Message) << "variable" << VD;
+    return;
+  }
+  llvm_unreachable("");
----------------
SimplyDanny wrote:

Unnecessary I think.

https://github.com/llvm/llvm-project/pull/90830