[clang] [Clang] Make '-Wglobal-constructors` work on the GNU attributes (PR #129917)

[Erich Keane via cfe-commits]

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@@ -7596,6 +7596,17 @@ void Sema::ProcessDeclAttributeList(
     D->setInvalidDecl();
   }
 
+  // Warn on global constructors and destructors created by attributes.
+  if (D->hasAttr<ConstructorAttr>() &&
+      !getDiagnostics().isIgnored(diag::warn_global_constructor,
+                                  D->getLocation()))
+    Diag(D->getLocation(), diag::warn_global_constructor)
+        << D->getSourceRange();
+  if (D->hasAttr<DestructorAttr>() &&
+      !getDiagnostics().isIgnored(diag::warn_global_destructor,
+                                  D->getLocation()))
+    Diag(D->getLocation(), diag::warn_global_destructor) << D->getSourceRange();
+
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erichkeane wrote:

Also, why bother checking if it is ignored?  We should just emit it, and count on the diagnostics engine to suppress it if it is ignored.  We typically only check `isIgnored` if we are going to do 'a lot' of work.

https://github.com/llvm/llvm-project/pull/129917