[clang] [lldb] [Clang] Improve Sema diagnostic performance for __builtin_counted_by_ref (PR #116719)

[via cfe-commits]

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@@ -6205,10 +6212,24 @@ bool Sema::CheckArgsForPlaceholders(MultiExprArg args) {
   for (size_t i = 0, e = args.size(); i != e; i++) {
     if (isPlaceholderToRemoveAsArg(args[i]->getType())) {
       ExprResult result = CheckPlaceholderExpr(args[i]);
-      if (result.isInvalid()) hasInvalid = true;
-      else args[i] = result.get();
+      if (result.isInvalid())
+        hasInvalid = true;
+      else
+        args[i] = result.get();
+    }
+
+    // The result of __builtin_counted_by_ref cannot be used as a function
+    // argument. It allows leaking and modification of bounds safety
+    // information.
+    if (const auto *CE = dyn_cast<CallExpr>(args[i]);
+        CE && CE->getBuiltinCallee() == Builtin::BI__builtin_counted_by_ref) {
+      hasInvalid = true;
+      Diag(CE->getExprLoc(),
+           diag::err_builtin_counted_by_ref_cannot_leak_reference)
+          << CE->getSourceRange();
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Sirraide wrote:

This probably shouldn’t be here anymore if there are no placeholder types involved anymore.

https://github.com/llvm/llvm-project/pull/116719