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// Copyright 2017 The Crashpad Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
#define CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
#include <stdint.h>
#include <cstddef>
#include <type_traits>
#include "base/numerics/safe_conversions.h"
#include "build/build_config.h"
namespace crashpad {
#if DOXYGEN
//! \brief Casts from a pointer type to an integer.
//!
//! Compared to `reinterpret_cast<>()`, FromPointerCast<>() defines whether a
//! pointer type is sign-extended or zero-extended. Casts to signed integral
//! types are sign-extended. Casts to unsigned integral types are zero-extended.
//!
//! Use FromPointerCast<>() instead of `reinterpret_cast<>()` when casting a
//! pointer to an integral type that may not be the same width as a pointer.
//! There is no need to prefer FromPointerCast<>() when casting to an integral
//! type that’s definitely the same width as a pointer, such as `uintptr_t` and
//! `intptr_t`.
template <typename To, typename From>
FromPointerCast(From from) {
return reinterpret_cast<To>(from);
}
#else // DOXYGEN
// Cast std::nullptr_t to any type.
//
// In C++14, the nullptr_t check could use std::is_null_pointer<From>::value
// instead of the is_same<remove_cv<From>::type, nullptr_t>::type construct.
template <typename To, typename From>
typename std::enable_if<
std::is_same<typename std::remove_cv<From>::type, std::nullptr_t>::value,
To>::type
FromPointerCast(From) {
return To();
}
// FromPointerCast<>() with a function pointer “From” type raises
// -Wnoexcept-type in GCC 7.2 if the function pointer type has a throw() or
// noexcept specification. This is the case for all standard C library functions
// provided by glibc. Various tests make use of FromPointerCast<>() with
// pointers to standard C library functions.
//
// Clang has the similar -Wc++1z-compat-mangling, which is not triggered by this
// pattern.
#if defined(COMPILER_GCC) && !defined(__clang__) && \
(__GNUC__ > 7 || (__GNUC__ == 7 && __GNUC_MINOR__ >= 2))
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wnoexcept-type"
#endif
// Cast a pointer to any other pointer type.
template <typename To, typename From>
typename std::enable_if<std::is_pointer<From>::value &&
std::is_pointer<To>::value,
To>::type
FromPointerCast(From from) {
return reinterpret_cast<To>(from);
}
// Cast a pointer to an integral type. Sign-extend when casting to a signed
// type, zero-extend when casting to an unsigned type.
template <typename To, typename From>
typename std::enable_if<std::is_pointer<From>::value &&
std::is_integral<To>::value,
To>::type
FromPointerCast(From from) {
const auto intermediate =
reinterpret_cast<typename std::conditional<std::is_signed<To>::value,
intptr_t,
uintptr_t>::type>(from);
if (sizeof(To) >= sizeof(From)) {
// If the destination integral type is at least as wide as the source
// pointer type, use static_cast<>() and just return it.
return static_cast<To>(intermediate);
}
// If the destination integral type is narrower than the source pointer type,
// use checked_cast<>().
return base::checked_cast<To>(intermediate);
}
#if defined(COMPILER_GCC) && !defined(__clang__) && \
(__GNUC__ > 7 || (__GNUC__ == 7 && __GNUC_MINOR__ >= 2))
#pragma GCC diagnostic pop
#endif
#endif // DOXYGEN
} // namespace crashpad
#endif // CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_