[clang] [Clang] strengthen checks for 'main' function to meet [basic.start.main] p2 requirements (PR #101853)

[via cfe-commits]

================
@@ -8052,15 +8061,13 @@ NamedDecl *Sema::ActOnVariableDeclarator(
   }
 
   // Special handling of variable named 'main'.
-  if (Name.getAsIdentifierInfo() && Name.getAsIdentifierInfo()->isStr("main") &&
-      NewVD->getDeclContext()->getRedeclContext()->isTranslationUnit() &&
-      !getLangOpts().Freestanding && !NewVD->getDescribedVarTemplate()) {
-
+  if (isMainVar(Name, NewVD) && !getLangOpts().Freestanding) {
     // C++ [basic.start.main]p3
     // A program that declares a variable main at global scope is ill-formed.
-    if (getLangOpts().CPlusPlus)
-      Diag(D.getBeginLoc(), diag::err_main_global_variable);
-
+    if (getLangOpts().CPlusPlus) {
+      if (!CheckLinkageSpecification(DC, NewVD))
----------------
Sirraide wrote:

```suggestion
```
This shouldn’t be here. Unlike with functions, it doesn’t matter whether the variable is `extern "C"` or not: a variable at the global scope that is named `main` is invalid regardless.

https://github.com/llvm/llvm-project/pull/101853