Re: [PATCH] PR libstdc++/71579 assert that type traits are not misused with an incomplete type

[Jonathan Wakely via Gcc-patches]

On 12/08/20 11:19 +0300, Antony Polukhin via Libstdc++ wrote:

Fixed patch for type traits hardening

Changelog

2020-08-12  Antony Polukhin  <antosh...@gmail.com>

   PR libstdc/71579
   * include/std/type_traits (invoke_result, is_nothrow_invocable_r)
   Add static_asserts to make sure that the argument of the type
   trait is not misused with incomplete types.
   (is_swappable_with, is_nothrow_swappable_with): Add static_asserts
   to make sure that the first and second arguments of the type trait
   are not misused with incomplete types.
   * testsuite/20_util/invoke_result/incomplete_neg.cc: New test.
   * testsuite/20_util/is_nothrow_invocable/incomplete_neg.cc: New test.
   * testsuite/20_util/is_nothrow_swappable/incomplete_neg.cc: New test.
   * testsuite/20_util/is_nothrow_swappable_with/incomplete_neg.cc: New
   test.
   * testsuite/20_util/is_swappable_with/incomplete_neg.cc: New test.

Thanks, pushed to master.

Do we also want to check
(std::__is_complete_or_unbounded(__type_identity<_ArgTypes>{}) && ...)
for invoke_result and the is_invocable traits?

We can use a fold expression there, because those traits are not
defined before C++17.