Clang was rejecting valid code where GNU style attributes preceded C++ style
attributes in template declarations as follows:
template<int a>
__attribute__((deprecated("oh no!"))) [[deprecated("oh no!")]] void foo();
This PR fixes the bug.
Differential Revision: https://reviews.llvm.org/D151837
We would previously reject valid input where GNU attributes preceded the
standard attributes on top-level declarations. A previous attribute
handling change had begun rejecting this whilst GCC does honour this
layout. In practice, this breaks use of `extern "C"` attributed
functions which use both standard and GNU attributes as experienced by
the Swift runtime.
Objective-C deserves an honourable mention for requiring some additional
special casing. Because attributes on declarations and definitions
differ in semantics, we need to replicate some of the logic for
detecting attributes to declarations to which they appertain cannot be
attributed. This should match the existing case for the application of
GNU attributes to interfaces, protocols, and implementations.
Take the opportunity to split out the tooling tests into two cases: ones
which process macros and ones which do not.
Special thanks to Aaron Ballman for the many hints and extensive rubber
ducking that was involved in identifying the various places where we
accidentally dropped attributes.
Differential Revision: https://reviews.llvm.org/D137979Fixes: #58229
Reviewed By: aaron.ballman, arphaman
In Clang today, we parse the different attribute syntaxes
(__attribute__, __declspec, and [[]]) in a fairly rigid order. This
leads to confusion for users when they guess the order incorrectly,
and leads to bug reports like PR24559 or necessitates changes like
D94788.
This patch adds a helper function to allow us to more easily parse
attributes in arbitrary order, and then updates all of the places
where we would parse two or more different syntaxes in a rigid order to
use the helper method. The patch does not attempt to handle Microsoft
attributes ([]) because those are ambiguous with other code constructs
and we don't have any attributes that use the syntax.
