[clang-tools-extra] [clang-tidy] Do not warn on const variables in misc-use-internal-linkage (PR #97969)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tidy

Author: Carlos Galvez (carlosgalvezp)

<details>
<summary>Changes</summary>

Since in C++ they already have implicit internal linkage.

Fixes #<!-- -->97947

---
Full diff: https://github.com/llvm/llvm-project/pull/97969.diff


2 Files Affected:

- (modified) clang-tools-extra/clang-tidy/misc/UseInternalLinkageCheck.cpp (+6) 
- (modified) clang-tools-extra/test/clang-tidy/checkers/misc/use-internal-linkage-var.cpp (+3) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/misc/UseInternalLinkageCheck.cpp b/clang-tools-extra/clang-tidy/misc/UseInternalLinkageCheck.cpp
index 44ccc2bc906a5b..c086e7721e02bd 100644
--- a/clang-tools-extra/clang-tidy/misc/UseInternalLinkageCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UseInternalLinkageCheck.cpp
@@ -121,6 +121,12 @@ void UseInternalLinkageCheck::check(const MatchFinder::MatchResult &Result) {
     return;
   }
   if (const auto *VD = Result.Nodes.getNodeAs<VarDecl>("var")) {
+    // In C++, const variables at file scope have implicit internal linkage,
+    // so we should not warn there. This is not the case in C.
+    // https://eel.is/c++draft/diff#basic-3
+    if (getLangOpts().CPlusPlus && VD->getType().isConstQualified())
+      return;
+
     DiagnosticBuilder DB = diag(VD->getLocation(), Message) << "variable" << VD;
     SourceLocation FixLoc = VD->getTypeSpecStartLoc();
     if (FixLoc.isInvalid() || FixLoc.isMacroID())
diff --git a/clang-tools-extra/test/clang-tidy/checkers/misc/use-internal-linkage-var.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc/use-internal-linkage-var.cpp
index 01b8d28e612301..6777ce4bb0265e 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/misc/use-internal-linkage-var.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/use-internal-linkage-var.cpp
@@ -42,3 +42,6 @@ int global_in_extern_c_1;
 }
 
 extern "C" int global_in_extern_c_2;
+
+const int const_global = 123;
+constexpr int constexpr_global = 123;

``````````

</details>


https://github.com/llvm/llvm-project/pull/97969