llvm/llvm/include/llvm/Support/Errc.h

//===- llvm/Support/Errc.h - Defines the llvm::errc enum --------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// While std::error_code works OK on all platforms we use, there are some
// some problems with std::errc that can be avoided by using our own
// enumeration:
//
// * std::errc is a namespace in some implementations. That means that ADL
//   doesn't work and it is sometimes necessary to write std::make_error_code
//   or in templates:
//   using std::make_error_code;
//   make_error_code(...);
//
//   with this enum it is safe to always just use make_error_code.
//
// * Some implementations define fewer names than others. This header has
//   the intersection of all the ones we support.
//
// * std::errc is just marked with is_error_condition_enum. This means that
//   common patterns like AnErrorCode == errc::no_such_file_or_directory take
//   4 virtual calls instead of two comparisons.
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_ERRC_H
#define LLVM_SUPPORT_ERRC_H

#include <system_error>

namespace llvm {
enum class errc { … };

inline std::error_code make_error_code(errc E) { … }
}

namespace std {
template <> struct is_error_code_enum<llvm::errc> : std::true_type { … };
}
#endif