libcxx/include/__cxx03/__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 <__cxx03/__config>
  13 #include <__cxx03/__utility/forward.h>
  14 #include <__cxx03/__utility/move.h>
  15 #include <__cxx03/new> // __throw_bad_alloc
  16 #include <__cxx03/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 <__cxx03/__undef_macros>
  24
  25 _LIBCPP_BEGIN_NAMESPACE_STD
  26 namespace __pstl {
  27
  28 template <class _BackendFunction, class... _Args>
  29 _LIBCPP_HIDE_FROM_ABI auto __handle_exception_impl(_Args&&... __args) noexcept {
  30   return _BackendFunction{}(std::forward<_Args>(__args)...);
  31 }
  32
  33 // This function is used to call a backend PSTL algorithm from a frontend algorithm.
  34 //
  35 // All PSTL backend algorithms return an optional denoting whether there was an
  36 // "infrastructure"-level failure (aka failure to allocate). This function takes
  37 // care of unwrapping that and throwing `bad_alloc()` in case there was a problem
  38 // in the underlying implementation.
  39 //
  40 // We must also be careful not to call any user code that could throw an exception
  41 // (such as moving or copying iterators) in here since that should terminate the
  42 // program, which is why we delegate to a noexcept helper below.
  43 template <class _BackendFunction, class... _Args>
  44 _LIBCPP_HIDE_FROM_ABI auto __handle_exception(_Args&&... __args) {
  45   auto __result = __pstl::__handle_exception_impl<_BackendFunction>(std::forward<_Args>(__args)...);
  46   if (__result == nullopt)
  47     std::__throw_bad_alloc();
  48   else
  49     return std::move(*__result);
  50 }
  51
  52 } // namespace __pstl
  53 _LIBCPP_END_NAMESPACE_STD
  54
  55 _LIBCPP_POP_MACROS
  56
  57 #endif // _LIBCPP___PSTL_HANDLE_EXCEPTION_H