[clang] [clang] Catch missing format attributes (PR #70024)

[Aaron Puchert via cfe-commits]

================
@@ -435,6 +435,86 @@ bool Sema::ConstantFoldAttrArgs(const AttributeCommonInfo &CI,
   return true;
 }
 
+// Warn if parent function does not have builtin function format attribute.
+void Sema::DiagnoseMissingFormatAttributes(NamedDecl *FDecl,
+                                           SourceLocation Loc) {
+  if (!FDecl)
+    return;
+
+  auto *FD = dyn_cast_or_null<FunctionDecl>(FDecl);
+  if (!FD)
+    return;
+
+  unsigned BuiltinID = FD->getBuiltinID(/*ConsiderWrappers=*/true);
+  
+  // Function is not builtin if it's builtin ID is 0.
+  if (!BuiltinID)
+    return;
----------------
aaronpuchert wrote:

What about calling a regular function that also has a `format` attribute? The GCC warning catches that as well.

https://github.com/llvm/llvm-project/pull/70024