libcxx/include/__pstl/handle_exception.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___PSTL_HANDLE_EXCEPTION_H
  10 #define _LIBCPP___PSTL_HANDLE_EXCEPTION_H
  11
  12 #include <__config>
  13 #include <__utility/forward.h>
  14 #include <__utility/move.h>
  15 #include <new> // __throw_bad_alloc
  16 #include <optional>
  17
  18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  19 #  pragma GCC system_header
  20 #endif
  21
  22 _LIBCPP_PUSH_MACROS
  23 #include <__undef_macros>
  24
  25 #if _LIBCPP_STD_VER >= 17
  26
  27 _LIBCPP_BEGIN_NAMESPACE_STD
  28 namespace __pstl {
  29
  30 template <class _BackendFunction, class... _Args>
  31 _LIBCPP_HIDE_FROM_ABI auto __handle_exception_impl(_Args&&... __args) noexcept {
  32   return _BackendFunction{}(std::forward<_Args>(__args)...);
  33 }
  34
  35 // This function is used to call a backend PSTL algorithm from a frontend algorithm.
  36 //
  37 // All PSTL backend algorithms return an optional denoting whether there was an
  38 // "infrastructure"-level failure (aka failure to allocate). This function takes
  39 // care of unwrapping that and throwing `bad_alloc()` in case there was a problem
  40 // in the underlying implementation.
  41 //
  42 // We must also be careful not to call any user code that could throw an exception
  43 // (such as moving or copying iterators) in here since that should terminate the
  44 // program, which is why we delegate to a noexcept helper below.
  45 template <class _BackendFunction, class... _Args>
  46 _LIBCPP_HIDE_FROM_ABI auto __handle_exception(_Args&&... __args) {
  47   auto __result = __pstl::__handle_exception_impl<_BackendFunction>(std::forward<_Args>(__args)...);
  48   if (__result == nullopt)
  49     std::__throw_bad_alloc();
  50   else
  51     return std::move(*__result);
  52 }
  53
  54 } // namespace __pstl
  55 _LIBCPP_END_NAMESPACE_STD
  56
  57 #endif // _LIBCPP_STD_VER >= 17
  58
  59 _LIBCPP_POP_MACROS
  60
  61 #endif // _LIBCPP___PSTL_HANDLE_EXCEPTION_H