libcxx/include/__exception/exception_ptr.h

//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___EXCEPTION_EXCEPTION_PTR_H
#define _LIBCPP___EXCEPTION_EXCEPTION_PTR_H

#include <__config>
#include <__cstddef/nullptr_t.h>
#include <__exception/operations.h>
#include <__memory/addressof.h>
#include <__memory/construct_at.h>
#include <__type_traits/decay.h>
#include <__type_traits/is_pointer.h>
#include <cstdlib>
#include <typeinfo>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

#ifndef _LIBCPP_ABI_MICROSOFT

#  if _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION

namespace __cxxabiv1 {

extern "C" {
_LIBCPP_OVERRIDABLE_FUNC_VIS void* __cxa_allocate_exception(size_t) throw();
_LIBCPP_OVERRIDABLE_FUNC_VIS void __cxa_free_exception(void*) throw();

struct __cxa_exception;
_LIBCPP_OVERRIDABLE_FUNC_VIS __cxa_exception* __cxa_init_primary_exception(
    void*,
    std::type_info*,
#    if defined(_WIN32)
    void(__thiscall*)(void*)) throw();
#    elif defined(__wasm__)
    // In Wasm, a destructor returns its argument
    void* (*)(void*)) throw();
#    else
    void (*)(void*)) throw();
#    endif
}

} // namespace __cxxabiv1

#  endif

#endif

_LIBCPP_BEGIN_UNVERSIONED_NAMESPACE_STD

#ifndef _LIBCPP_ABI_MICROSOFT

class _LIBCPP_EXPORTED_FROM_ABI exception_ptr {
  void* __ptr_;

  static exception_ptr __from_native_exception_pointer(void*) _NOEXCEPT;

  template <class _Ep>
  friend _LIBCPP_HIDE_FROM_ABI exception_ptr __make_exception_ptr_explicit(_Ep&) _NOEXCEPT;

public:
  // exception_ptr is basically a COW string so it is trivially relocatable.
  // It is also replaceable because assignment has normal value semantics.
  using __trivially_relocatable _LIBCPP_NODEBUG = exception_ptr;
  using __replaceable _LIBCPP_NODEBUG           = exception_ptr;

  _LIBCPP_HIDE_FROM_ABI exception_ptr() _NOEXCEPT : __ptr_() {}
  _LIBCPP_HIDE_FROM_ABI exception_ptr(nullptr_t) _NOEXCEPT : __ptr_() {}

  exception_ptr(const exception_ptr&) _NOEXCEPT;
  exception_ptr& operator=(const exception_ptr&) _NOEXCEPT;
  ~exception_ptr() _NOEXCEPT;

  _LIBCPP_HIDE_FROM_ABI explicit operator bool() const _NOEXCEPT { return __ptr_ != nullptr; }

  friend _LIBCPP_HIDE_FROM_ABI bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT {
    return __x.__ptr_ == __y.__ptr_;
  }

  friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT {
    return !(__x == __y);
  }

  friend _LIBCPP_EXPORTED_FROM_ABI exception_ptr current_exception() _NOEXCEPT;
  friend _LIBCPP_EXPORTED_FROM_ABI void rethrow_exception(exception_ptr);
};

#  if _LIBCPP_HAS_EXCEPTIONS
#    if _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION
template <class _Ep>
_LIBCPP_HIDE_FROM_ABI exception_ptr __make_exception_ptr_explicit(_Ep& __e) _NOEXCEPT {
  using _Ep2 = __decay_t<_Ep>;
  void* __ex = __cxxabiv1::__cxa_allocate_exception(sizeof(_Ep));
#      ifdef __wasm__
  auto __cleanup = [](void* __p) -> void* {
    std::__destroy_at(static_cast<_Ep2*>(__p));
    return __p;
  };
#      else
  auto __cleanup = [](void* __p) { std::__destroy_at(static_cast<_Ep2*>(__p)); };
#      endif
  (void)__cxxabiv1::__cxa_init_primary_exception(__ex, const_cast<std::type_info*>(&typeid(_Ep)), __cleanup);

  try {
    ::new (__ex) _Ep2(__e);
    return exception_ptr::__from_native_exception_pointer(__ex);
  } catch (...) {
    __cxxabiv1::__cxa_free_exception(__ex);
    return current_exception();
  }
}
#    endif

template <class _Ep>
_LIBCPP_HIDE_FROM_ABI exception_ptr __make_exception_ptr_via_throw(_Ep& __e) _NOEXCEPT {
  try {
    throw __e;
  } catch (...) {
    return current_exception();
  }
}

template <class _Ep>
_LIBCPP_HIDE_FROM_ABI exception_ptr make_exception_ptr(_Ep __e) _NOEXCEPT {
  // Objective-C exceptions are thrown via pointer. When throwing an Objective-C exception,
  // Clang generates a call to `objc_exception_throw` instead of the usual `__cxa_throw`.
  // That function creates an exception with a special Objective-C typeinfo instead of
  // the usual C++ typeinfo, since that is needed to implement the behavior documented
  // at [1]).
  //
  // Because of this special behavior, we can't create an exception via `__cxa_init_primary_exception`
  // for Objective-C exceptions, otherwise we'd bypass `objc_exception_throw`. See https://llvm.org/PR135089.
  //
  // [1]:
  // https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Exceptions/Articles/Exceptions64Bit.html
  if _LIBCPP_CONSTEXPR (is_pointer<_Ep>::value) {
    return std::__make_exception_ptr_via_throw(__e);
  }

#    if _LIBCPP_AVAILABILITY_HAS_INIT_PRIMARY_EXCEPTION && !defined(_LIBCPP_CXX03_LANG)
  return std::__make_exception_ptr_explicit(__e);
#    else
  return std::__make_exception_ptr_via_throw(__e);
#    endif
}
#  else  // !_LIBCPP_HAS_EXCEPTIONS
template <class _Ep>
_LIBCPP_HIDE_FROM_ABI exception_ptr make_exception_ptr(_Ep) _NOEXCEPT {
  std::abort();
}
#  endif // _LIBCPP_HAS_EXCEPTIONS

#else // _LIBCPP_ABI_MICROSOFT

class _LIBCPP_EXPORTED_FROM_ABI exception_ptr {
  _LIBCPP_DIAGNOSTIC_PUSH
  _LIBCPP_CLANG_DIAGNOSTIC_IGNORED("-Wunused-private-field")
  void* __ptr1_;
  void* __ptr2_;
  _LIBCPP_DIAGNOSTIC_POP

public:
  exception_ptr() _NOEXCEPT;
  exception_ptr(nullptr_t) _NOEXCEPT;
  exception_ptr(const exception_ptr& __other) _NOEXCEPT;
  exception_ptr& operator=(const exception_ptr& __other) _NOEXCEPT;
  exception_ptr& operator=(nullptr_t) _NOEXCEPT;
  ~exception_ptr() _NOEXCEPT;
  explicit operator bool() const _NOEXCEPT;
};

_LIBCPP_EXPORTED_FROM_ABI bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT;

inline _LIBCPP_HIDE_FROM_ABI bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT {
  return !(__x == __y);
}

_LIBCPP_EXPORTED_FROM_ABI void swap(exception_ptr&, exception_ptr&) _NOEXCEPT;

_LIBCPP_EXPORTED_FROM_ABI exception_ptr __copy_exception_ptr(void* __except, const void* __ptr);
_LIBCPP_EXPORTED_FROM_ABI exception_ptr current_exception() _NOEXCEPT;
[[__noreturn__]] _LIBCPP_EXPORTED_FROM_ABI void rethrow_exception(exception_ptr);

// This is a built-in template function which automagically extracts the required
// information.
template <class _E>
void* __GetExceptionInfo(_E);

template <class _Ep>
_LIBCPP_HIDE_FROM_ABI exception_ptr make_exception_ptr(_Ep __e) _NOEXCEPT {
  return __copy_exception_ptr(std::addressof(__e), __GetExceptionInfo(__e));
}

#endif // _LIBCPP_ABI_MICROSOFT
_LIBCPP_END_UNVERSIONED_NAMESPACE_STD

#endif // _LIBCPP___EXCEPTION_EXCEPTION_PTR_H