bslstl_iserrorcodeenum.h

Go to the documentation of this file.

/// @file bslstl_iserrorcodeenum.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslstl_iserrorcodeenum.h                                           -*-C++-*-
#ifndef INCLUDED_BSLSTL_ISERRORCODEENUM
#define INCLUDED_BSLSTL_ISERRORCODEENUM
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
// BDE_VERIFY pragma: -TP25  // CLASSES are not defined in C++11
 
/// @defgroup bslstl_iserrorcodeenum bslstl_iserrorcodeenum
/// @brief  Provide a compliant standard `is_error_code_enum` trait.
/// @addtogroup bsl
/// @{
/// @addtogroup bslstl
/// @{
/// @addtogroup bslstl_iserrorcodeenum
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslstl_iserrorcodeenum-purpose"> Purpose</a>
/// * <a href="#bslstl_iserrorcodeenum-classes"> Classes </a>
/// * <a href="#bslstl_iserrorcodeenum-macros"> Macros </a>
/// * <a href="#bslstl_iserrorcodeenum-description"> Description </a>
///   * <a href="#bslstl_iserrorcodeenum-usage"> Usage </a>
///     * <a href="#bslstl_iserrorcodeenum-example-1-dedicated-error-values"> Example 1: Dedicated Error Values </a>
///
/// # Purpose {#bslstl_iserrorcodeenum-purpose}
/// Provide a compliant standard `is_error_code_enum` trait.
///
/// # Classes {#bslstl_iserrorcodeenum-classes}
///
/// -  bsl::is_error_code_enum: standard compliant version of `is_error_code_enum`
///
/// # Macros {#bslstl_iserrorcodeenum-macros}
///
/// -  BSL_IS_ERROR_CODE_ENUM_NAMESPACE:  namespace to specialize the trait
///
/// **Canonical header:**  bsl_system_error.h
///
/// # Description {#bslstl_iserrorcodeenum-description}
/// This component defines a class template,
/// `bsl::is_error_code_enum`, intended to be specialized for enumeration types
/// that are designated as error codes for the `<system_error>` facility.  In
/// C++11 mode, the vendor-supplied `<system_error>` implementation is used
/// instead, and the corresponding names from `std` are imported into `bsl`.
/// This component also defines a macro, `BSL_IS_ERROR_CODE_ENUM_NAMESPACE`, to
/// be used as the namespace in which to write specializations of
/// `is_error_code_enum`.
///
/// ## Usage {#bslstl_iserrorcodeenum-usage}
///
///
/// In this section we show intended use of this component.
///
/// ### Example 1: Dedicated Error Values {#bslstl_iserrorcodeenum-example-1-dedicated-error-values}
///
///
/// Suppose we have a dedicated system with a set of possible errors, and we
/// want to be able to throw descriptive exceptions when an error occurs.  We
/// need to work with the `<system_error>` facility to support this, starting by
/// marking the enumeration type that defines the error literals as eligible to
/// participate.  We can use `bsl::is_error_code_enum` to do this.
///
/// First, we define the set of error values for our system.
/// @code
/// struct CarError {
///     // TYPES
///     enum Enum {
///         k_CAR_WHEELS_CAME_OFF = 1,
///         k_CAR_ENGINE_FELL_OUT = 2
///     };
/// };
/// @endcode
/// Then, we enable the trait marking this as an error code.
/// @code
/// namespace BSL_IS_ERROR_CODE_ENUM_NAMESPACE {
/// template <> struct is_error_code_enum<CarError::Enum>
/// : bsl::public true_type { };
/// }  // close namespace BSL_IS_ERROR_CODE_ENUM_NAMESPACE
/// @endcode
/// Finally, we verify that the trait marks our type as eligible.
/// @code
/// assert(is_error_code_enum<CarError::Enum>::value);
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslstl
 * @{
 */
/** @addtogroup bslstl_iserrorcodeenum
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_integralconstant.h>
 
#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
#include <bsls_libraryfeatures.h>
 
#ifndef BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
#include <bsls_nativestd.h>
#endif // BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
 
// BDE_VERIFY pragma: -SLM01  // Do not complain about macro leaking
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY
 
#include <system_error>
 
#define BSL_IS_ERROR_CODE_ENUM_NAMESPACE std
 
namespace bsl {
using std::is_error_code_enum;
 
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY
using std::is_error_code_enum_v;
#elif defined BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
template <class TYPE>
#ifdef BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES
inline
#endif
BSLS_KEYWORD_CONSTEXPR bool is_error_code_enum_v =
    is_error_code_enum<TYPE>::value;
#endif
}  // close namespace bsl
 
#else
 
#define BSL_IS_ERROR_CODE_ENUM_NAMESPACE bsl
 
namespace bsl {
                         // =========================
                         // struct is_error_code_enum
                         // =========================
 
/// This class template represents a trait defining whether the specified
/// enumeration type `TYPE` is to be treated as an error code by the
/// @ref error_code  template methods.
template <class TYPE>
struct is_error_code_enum : public bsl::false_type
{
};
 
}  // close namespace bsl
 
#endif
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2019 Bloomberg Finance L.P.
//
// 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.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */