libcxx/include/__exception/nested_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___EXCEPTION_NESTED_EXCEPTION_H
  10 #define _LIBCPP___EXCEPTION_NESTED_EXCEPTION_H
  11
  12 #include <__config>
  13 #include <__exception/exception_ptr.h>
  14 #include <__memory/addressof.h>
  15 #include <__type_traits/decay.h>
  16 #include <__type_traits/enable_if.h>
  17 #include <__type_traits/integral_constant.h>
  18 #include <__type_traits/is_base_of.h>
  19 #include <__type_traits/is_class.h>
  20 #include <__type_traits/is_constructible.h>
  21 #include <__type_traits/is_convertible.h>
  22 #include <__type_traits/is_final.h>
  23 #include <__type_traits/is_polymorphic.h>
  24 #include <__utility/forward.h>
  25
  26 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  27 #  pragma GCC system_header
  28 #endif
  29
  30 namespace std { // purposefully not using versioning namespace
  31
  32 class _LIBCPP_EXPORTED_FROM_ABI nested_exception {
  33   exception_ptr __ptr_;
  34
  35 public:
  36   nested_exception() _NOEXCEPT;
  37   _LIBCPP_HIDE_FROM_ABI nested_exception(const nested_exception&) _NOEXCEPT            = default;
  38   _LIBCPP_HIDE_FROM_ABI nested_exception& operator=(const nested_exception&) _NOEXCEPT = default;
  39   virtual ~nested_exception() _NOEXCEPT;
  40
  41   // access functions
  42   [[__noreturn__]] void rethrow_nested() const;
  43   _LIBCPP_HIDE_FROM_ABI exception_ptr nested_ptr() const _NOEXCEPT { return __ptr_; }
  44 };
  45
  46 template <class _Tp>
  47 struct __nested : public _Tp, public nested_exception {
  48   _LIBCPP_HIDE_FROM_ABI explicit __nested(const _Tp& __t) : _Tp(__t) {}
  49 };
  50
  51 #if _LIBCPP_HAS_EXCEPTIONS
  52 template <class _Tp, class _Up, bool>
  53 struct __throw_with_nested;
  54
  55 template <class _Tp, class _Up>
  56 struct __throw_with_nested<_Tp, _Up, true> {
  57   [[__noreturn__]] static inline _LIBCPP_HIDE_FROM_ABI void __do_throw(_Tp&& __t) {
  58     throw __nested<_Up>(std::forward<_Tp>(__t));
  59   }
  60 };
  61
  62 template <class _Tp, class _Up>
  63 struct __throw_with_nested<_Tp, _Up, false> {
  64   [[__noreturn__]] static inline _LIBCPP_HIDE_FROM_ABI void __do_throw(_Tp&& __t) { throw std::forward<_Tp>(__t); }
  65 };
  66 #endif
  67
  68 template <class _Tp>
  69 [[__noreturn__]] _LIBCPP_HIDE_FROM_ABI void throw_with_nested(_Tp&& __t) {
  70 #if _LIBCPP_HAS_EXCEPTIONS
  71   using _Up = __decay_t<_Tp>;
  72   static_assert(is_copy_constructible<_Up>::value, "type thrown must be CopyConstructible");
  73   __throw_with_nested<_Tp,
  74                       _Up,
  75                       is_class<_Up>::value && !is_base_of<nested_exception, _Up>::value &&
  76                           !__libcpp_is_final<_Up>::value>::__do_throw(std::forward<_Tp>(__t));
  77 #else
  78   ((void)__t);
  79   // FIXME: Make this abort
  80 #endif
  81 }
  82
  83 template <class _From, class _To>
  84 struct __can_dynamic_cast
  85     : _BoolConstant< is_polymorphic<_From>::value &&
  86                      (!is_base_of<_To, _From>::value || is_convertible<const _From*, const _To*>::value)> {};
  87
  88 template <class _Ep, __enable_if_t< __can_dynamic_cast<_Ep, nested_exception>::value, int> = 0>
  89 inline _LIBCPP_HIDE_FROM_ABI void rethrow_if_nested(const _Ep& __e) {
  90   const nested_exception* __nep = dynamic_cast<const nested_exception*>(std::addressof(__e));
  91   if (__nep)
  92     __nep->rethrow_nested();
  93 }
  94
  95 template <class _Ep, __enable_if_t<!__can_dynamic_cast<_Ep, nested_exception>::value, int> = 0>
  96 inline _LIBCPP_HIDE_FROM_ABI void rethrow_if_nested(const _Ep&) {}
  97
  98 } // namespace std
  99
 100 #endif // _LIBCPP___EXCEPTION_NESTED_EXCEPTION_H