2b26ee6e79
The `std::error_code`/`std::error_category` functionality is designed to support multiple error domains. On Unix, both system calls and libc functions return the same error codes, and thus, libc++ today treats `generic_category()` and `system_category()` as being equivalent. However, on Windows, libc functions return `errno.h` error codes in the `errno` global, but system calls return the very different `winerror.h` error codes via `GetLastError()`. As such, there is a need to map the winerror.h error codes into generic errno codes. In libc++, however, the system_error facility does not implement this mapping; instead the mapping is hidden inside libc++, used directly by the std::filesystem implementation. That has a few problems: 1. For std::filesystem APIs, the concrete windows error number is lost, before users can see it. The intent of the distinction between std::error_code and std::error_condition is that the error_code return has the original (potentially more detailed) error code. 2. User-written code which calls Windows system APIs requires this same mapping, so it also can also return error_code objects that other (cross-platform) code can understand. After this commit, an `error_code` with `generic_category()` is used to report an error from `errno`, and, on Windows only, an `error_code` with `system_category()` is used to report an error from `GetLastError()`. On Unix, system_category remains identity-mapped to generic_category, but is never used by libc++ itself. The windows error code mapping is moved into system_error, so that conversion of an `error_code` to `error_condition` correctly translates the `system_category()` code into a `generic_category()` code, when appropriate. This allows code like: `error_code(GetLastError(), system_category()) == errc::invalid_argument` to work as expected -- as it does with MSVC STL. (Continued from old phabricator review [D151493](https://reviews.llvm.org/D151493))
58 lines
2.1 KiB
C++
58 lines
2.1 KiB
C++
// -*- C++ -*-
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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H
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#define _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H
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#include <__config>
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#include <__system_error/error_category.h>
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#include <__system_error/error_code.h>
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#include <__verbose_abort>
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#include <stdexcept>
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#include <string>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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class _LIBCPP_EXPORTED_FROM_ABI system_error : public runtime_error {
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error_code __ec_;
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public:
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system_error(error_code __ec, const string& __what_arg);
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system_error(error_code __ec, const char* __what_arg);
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system_error(error_code __ec);
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system_error(int __ev, const error_category& __ecat, const string& __what_arg);
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system_error(int __ev, const error_category& __ecat, const char* __what_arg);
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system_error(int __ev, const error_category& __ecat);
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_LIBCPP_HIDE_FROM_ABI system_error(const system_error&) _NOEXCEPT = default;
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~system_error() _NOEXCEPT override;
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_LIBCPP_HIDE_FROM_ABI const error_code& code() const _NOEXCEPT { return __ec_; }
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};
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// __ev is expected to be an error in the generic_category domain (e.g. from
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// errno, or std::errc::*), not system_category (e.g. from windows syscalls).
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[[__noreturn__]] _LIBCPP_EXPORTED_FROM_ABI void __throw_system_error(int __ev, const char* __what_arg);
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[[__noreturn__]] _LIBCPP_HIDE_FROM_ABI inline void __throw_system_error(error_code __ec, const char* __what_arg) {
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#if _LIBCPP_HAS_EXCEPTIONS
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throw system_error(__ec, __what_arg);
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#else
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_LIBCPP_VERBOSE_ABORT(
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"system_error was thrown in -fno-exceptions mode with error %i and message \"%s\"", __ec.value(), __what_arg);
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#endif
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}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___SYSTEM_ERROR_SYSTEM_ERROR_H
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