[clang] Allow attributes on first constructor argument in pre-C++11

clang/docs/ReleaseNotes.rst

@@ -349,6 +349,8 @@ Bug Fixes to C++ Support
   authentication enabled. (#GH152601)
 - Fix the check for narrowing int-to-float conversions, so that they are detected in
   cases where converting the float back to an integer is undefined behaviour (#GH157067).
+- Stop rejecting C++11-style attributes on the first argument of constructors in older
+  standards. (#GH156809).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Parse/ParseDecl.cpp

@@ -6007,10 +6007,9 @@ bool Parser::isConstructorDeclarator(bool IsUnqualified, bool DeductionGuide,
 
   // A C++11 attribute here signals that we have a constructor, and is an
   // attribute on the first constructor parameter.
-  if (getLangOpts().CPlusPlus11 &&
-      isCXX11AttributeSpecifier(/*Disambiguate*/ false,
+  if (isCXX11AttributeSpecifier(/*Disambiguate*/ false,
                                 /*OuterMightBeMessageSend*/ true) !=
-          CXX11AttributeKind::NotAttributeSpecifier) {
+      CXX11AttributeKind::NotAttributeSpecifier) {
     return true;
   }
 

clang/test/Parser/cxx03-attributes.cpp

@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++03 %s
+// expected-no-diagnostics
+
+struct S {
+    S([[clang::lifetimebound]] int&) {}
+};