[libcxx-commits] [PATCH] D140731: [libc++][CI] Fixes robust against ADL for C++03.

[Nikolas Klauser via Phabricator via libcxx-commits]

philnik added a comment.

In D140731#4021229 <https://reviews.llvm.org/D140731#4021229>, @Mordante wrote:

> In D140731#4020155 <https://reviews.llvm.org/D140731#4020155>, @philnik wrote:
>
>> Where does this fire? `noexcept(cond)` should never be used in C++03.
>
> `include/__functional/invoke.h` lines 431 and 438 are the only two places
>
>   template <class _Ret, class _Fp, class ..._Args>
>   struct __nothrow_invokable_r_imp<true, false, _Ret, _Fp, _Args...>
>   {
>       typedef __nothrow_invokable_r_imp _ThisT;
>     
>       template <class _Tp>
>       static void __test_noexcept(_Tp) _NOEXCEPT;
>     
>       static const bool value = noexcept(_ThisT::__test_noexcept<_Ret>(  // 431
>           _VSTD::__invoke(declval<_Fp>(), declval<_Args>()...)));
>   };    
>     
>   template <class _Ret, class _Fp, class ..._Args>
>   struct __nothrow_invokable_r_imp<true, true, _Ret, _Fp, _Args...>
>   {
>       static const bool value = noexcept(                                 / 438
>           _VSTD::__invoke(declval<_Fp>(), declval<_Args>()...)); 
>   };

IMO we should fix the code here. In C++03 the values are always false anyways, so we could just make this

  template <class _Ret, class _Fp, class ..._Args>
  struct __nothrow_invokable_r_imp<true, false, _Ret, _Fp, _Args...>
  {
      typedef __nothrow_invokable_r_imp _ThisT;
    
      template <class _Tp>
      static void __test_noexcept(_Tp) _NOEXCEPT;
  
  #ifdef _LIBCPP_CXX03_LANG
      static const bool value = false;
  #else
      static const bool value = noexcept(_ThisT::__test_noexcept<_Ret>(_VSTD::__invoke(declval<_Fp>(), declval<_Args>()...)));
  #endif
  };    
    
  template <class _Ret, class _Fp, class ..._Args>
  struct __nothrow_invokable_r_imp<true, true, _Ret, _Fp, _Args...>
  {
  #ifdef _LIBCPP_CXX03_LANG
      static const bool value = false;
  #else
      static const bool value = noexcept(_VSTD::__invoke(declval<_Fp>(), declval<_Args>()...)); 
  #endif
  };

or something similar.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D140731/new/

https://reviews.llvm.org/D140731