[clang-tools-extra] [clang-tidy][libc] Fix namespace check with macro (PR #68134)

[Piotr Zegar via cfe-commits]

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@@ -45,18 +46,21 @@ void CalleeNamespaceCheck::check(const MatchFinder::MatchResult &Result) {
   if (FuncDecl->getBuiltinID() != 0)
     return;
 
-  // If the outermost namespace of the function is __llvm_libc, we're good.
+  // If the outermost namespace of the function is a macro that starts with
+  // __llvm_libc, we're good.
   const auto *NS = dyn_cast<NamespaceDecl>(getOutermostNamespace(FuncDecl));
-  if (NS && NS->getName() == "__llvm_libc")
+  if (NS && Result.SourceManager->isMacroBodyExpansion(NS->getLocation()) &&
+      NS->getName().starts_with(RequiredNamespaceStart))
     return;
 
   const DeclarationName &Name = FuncDecl->getDeclName();
   if (Name.isIdentifier() &&
       IgnoredFunctions.contains(Name.getAsIdentifierInfo()->getName()))
     return;
 
-  diag(UsageSiteExpr->getBeginLoc(), "%0 must resolve to a function declared "
-                                     "within the '__llvm_libc' namespace")
+  diag(UsageSiteExpr->getBeginLoc(),
+       "%0 must resolve to a function declared "
+       "within the namespace defined by the 'LIBC_NAMESPACE' macro")
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PiotrZSL wrote:

Note: use RequiredNamespaceMacroName  instead of harcoded LIBC_NAMESPACE here

https://github.com/llvm/llvm-project/pull/68134