bslmf_ismemberobjectpointer.h

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/// @file bslmf_ismemberobjectpointer.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmf_ismemberobjectpointer.h                                      -*-C++-*-
#ifndef INCLUDED_BSLMF_ISMEMBEROBJECTPOINTER
#define INCLUDED_BSLMF_ISMEMBEROBJECTPOINTER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmf_ismemberobjectpointer bslmf_ismemberobjectpointer
/// @brief  Provide a compile-time check for member object pointer types.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmf
/// @{
/// @addtogroup bslmf_ismemberobjectpointer
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmf_ismemberobjectpointer-purpose"> Purpose</a>
/// * <a href="#bslmf_ismemberobjectpointer-classes"> Classes </a>
/// * <a href="#bslmf_ismemberobjectpointer-description"> Description </a>
///   * <a href="#bslmf_ismemberobjectpointer-usage"> Usage </a>
///     * <a href="#bslmf_ismemberobjectpointer-example-1-verify-member-object-pointer-types"> Example 1: Verify Member Object Pointer Types </a>
///
/// # Purpose {#bslmf_ismemberobjectpointer-purpose}
/// Provide a compile-time check for member object pointer types.
///
/// # Classes {#bslmf_ismemberobjectpointer-classes}
///
/// -  bsl::is_member_object_pointer: standard meta-function
/// -  bsl::is_member_object_pointer_v: the result value of the meta-function
///
/// @see  bslmf_integralconstant, bslmf_ismemberfunctionpointer
///
/// # Description {#bslmf_ismemberobjectpointer-description}
/// This component defines a meta-function,
/// `bsl::is_member_object_pointer` and a template variable
/// `bsl::is_member_object_pointer_v`, that represents the result value of the
/// `bsl::is_member_object_pointer` meta-function, that may be used to query
/// whether a type is a pointer to non-static member object type.
///
/// `bsl::is_member_object_pointer` meets the requirements of the
/// `is_member_object_pointer` template defined in the C++11 standard
/// [meta.unary.cat].
///
/// Note that the template variable `is_member_object_pointer_v` is defined in
/// the C++17 standard as an inline variable.  If the current compiler supports
/// the inline variable C++17 compiler feature,
/// `bsl::is_member_object_pointer_v` is defined as an `inline constexpr bool`
/// variable.  Otherwise, if the compiler supports the variable templates C++14
/// compiler feature, `bsl::is_member_object_pointer_v` is defined as a
/// non-inline `constexpr bool` variable.  See
/// `BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES` and
/// `BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES` macros in
/// bsls_compilerfeatures component for details.
///
/// ## Usage {#bslmf_ismemberobjectpointer-usage}
///
///
/// In this section we show intended use of this component.
///
/// ### Example 1: Verify Member Object Pointer Types {#bslmf_ismemberobjectpointer-example-1-verify-member-object-pointer-types}
///
///
/// Suppose that we want to assert whether a set of types are pointers to member
/// object types.
///
/// First, we create a user-defined type `MyStruct`:
/// @code
/// struct MyStruct
/// {
/// };
/// @endcode
/// Now, we create a `typedef` for a member object pointer type:
/// @code
/// typedef int MyStruct::* DataMemPtr;
/// @endcode
/// Finally, we instantiate the `bsl::is_member_object_pointer` template for a
/// non-member data type and the `MyStructDataPtr` type, and assert the `value`
/// static data member of each instantiation:
/// @code
/// assert(false == bsl::is_member_object_pointer<int*>::value);
/// assert(true  == bsl::is_member_object_pointer<DataMemPtr>::value);
/// @endcode
/// Note that if the current compiler supports the variable templates C++14
/// feature then we can re-write the snippet of code above using the
/// `bsl::is_member_object_pointer_v` variable as follows:
/// @code
/// #ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
///   assert(false == bsl::is_member_object_pointer_v<int*>);
///   assert(true  == bsl::is_member_object_pointer_v<DataMemPtr>);
/// #endif
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslmf
 * @{
 */
/** @addtogroup bslmf_ismemberobjectpointer
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_integralconstant.h>
#include <bslmf_isconst.h>
#include <bslmf_isfunction.h>
 
#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
#include <bsls_platform.h>
 
#ifndef BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
#include <bslmf_ismemberfunctionpointer.h>
#endif // BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
 
#if !defined(BSLS_PLATFORM_CMP_IBM)
namespace bsl {
 
                       // ===============================
                       // struct is_member_object_pointer
                       // ===============================
 
/// This `struct` template implements the `is_member_object_pointer`
/// meta-function defined in the C++11 standard [meta.unary.cat] to
/// determine if the (template parameter) `t_TYPE` is a pointer to
/// non-static data member type.  This `struct` derives from
/// `bsl::true_type` if the `t_TYPE` is a pointer to non-static data member
/// type, and from `bsl::false_type` otherwise.
template <class t_TYPE>
struct is_member_object_pointer : false_type {
};
 
#ifdef BSLS_PLATFORM_CMP_MSVC
# pragma warning(push)
# pragma warning(disable: 4180)  // cv-qualifier has no effect on function type
#endif
 
/// Partial specialization relies on the principle that only object types
/// can be `const`-qualified.  Reference-types and function-types do not
/// retain the `const` qualifier when added in this manner, and there are
/// no `void` class members.
template <class t_TYPE, class t_CLASS>
struct is_member_object_pointer<t_TYPE t_CLASS::*>
: is_const<const t_TYPE>::type {
};
 
#ifdef BSLS_PLATFORM_CMP_MSVC
# pragma warning(pop)
#endif
 
/// Partial specialization relies on the principle that only object types
/// can be `const`-qualified.  Reference-types and function-types do not
/// retain the `const` qualifier when added in this manner, and there are
/// no `void` class members.
template <class t_TYPE, class t_CLASS>
struct is_member_object_pointer<t_TYPE t_CLASS::*const>
: is_const<const t_TYPE>::type {
};
 
/// Partial specialization relies on the principle that only object types
/// can be `const`-qualified.  Reference-types and function-types do not
/// retain the `const` qualifier when added in this manner, and there are
/// no `void` class members.
template <class t_TYPE, class t_CLASS>
struct is_member_object_pointer<t_TYPE t_CLASS::*volatile>
: is_const<const t_TYPE>::type {
};
 
/// Partial specialization relies on the principle that only object types
/// can be `const`-qualified.  Reference-types and function-types do not
/// retain the `const` qualifier when added in this manner, and there are
/// no `void` class members.
template <class t_TYPE, class t_CLASS>
struct is_member_object_pointer<t_TYPE t_CLASS::*const volatile>
: is_const<const t_TYPE>::type {
};
 
}  // close namespace bsl
#else
// The IBM xlC compiler produces parses an error when trying to add 'const' to
// a function type, so leans on the original BDE implementation of this trait.
// Note that this implementation fails on all other compilers for member
// functions with a C-style elipsis, erroneously reporting such functions as
// data members.  However, xlC appears to have sufficient compenstating bugs
// that this implementation gives the correct result in such cases too.
 
 
namespace bslmf {
 
                       // ================================
                       // struct IsPointerToMemberData_Imp
                       // ================================
 
template <class t_TYPE>
struct IsPointerToMemberData_Imp : bsl::false_type {
    // This 'struct' template provides a meta-function to determine whether the
    // (template parameter) 't_TYPE' is a pointer to non-static data member
    // type.  This generic default template derives from 'bsl::false_type'.  A
    // template specialization is provided (below) that derives from
    // 'bsl::true_type'.
};
 
template <class t_TYPE, class t_CLASS>
struct IsPointerToMemberData_Imp<t_TYPE t_CLASS::*>
: bsl::integral_constant<bool, !bsl::is_function<t_TYPE>::value> {
    // This partial specialization of 'IsPointerToMemberData_Imp' derives from
    // 'bsl::true_type' for when the (template parameter) 't_TYPE' is a pointer
    // to non-static data member type.
};
 
}  // close package namespace
 
 
namespace bsl {
 
                       // ===============================
                       // struct is_member_object_pointer
                       // ===============================
 
template <class t_TYPE>
struct is_member_object_pointer
: BloombergLP::bslmf::IsPointerToMemberData_Imp<t_TYPE>::type {
    // This 'struct' template implements the 'is_member_object_pointer'
    // meta-function defined in the C++11 standard [meta.unary.cat] to
    // determine if the (template parameter) 't_TYPE' is a pointer to
    // non-static data member type.  This 'struct' derives from
    // 'bsl::true_type' if the 't_TYPE' is a pointer to non-static data member
    // type, and from 'bsl::false_type' otherwise.
};
 
template <class t_TYPE>
struct is_member_object_pointer<const t_TYPE>
: BloombergLP::bslmf::IsPointerToMemberData_Imp<t_TYPE>::type {
    // Partial specialization to handle 'const'-qualified pointer-to-member
    // objects.
};
 
template <class t_TYPE>
struct is_member_object_pointer<volatile t_TYPE>
: BloombergLP::bslmf::IsPointerToMemberData_Imp<t_TYPE>::type {
    // Partial specialization to handle 'volatile'-qualified pointer-to-member
    // objects.
};
 
template <class t_TYPE>
struct is_member_object_pointer<const volatile t_TYPE>
: BloombergLP::bslmf::IsPointerToMemberData_Imp<t_TYPE>::type {
    // Partial specialization to handle 'const volatile'-qualified
    // pointer-to-member objects.
};
 
}  // close namespace bsl
#endif
 
#ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
namespace bsl {
 
/// This template variable represents the result value of the
/// `bsl::is_member_object_pointer` meta-function.
template <class t_TYPE>
BSLS_KEYWORD_INLINE_VARIABLE constexpr bool is_member_object_pointer_v =
                                       is_member_object_pointer<t_TYPE>::value;
}  // close namespace bsl
#endif
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2013-2018 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */