BDE 4.14.0 Production release
Loading...
Searching...
No Matches
Macros | Variables
bsls_libraryfeatures
Group bsl » Package bsls

Macros

#define BSLS_LIBRARYFEATURES_DETECTION_IN_PROGRESS
 
#define BSLS_LIBRARYFEATURES_HAS_C90_GETS   1
 
#define BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR   1
 
#define BSLS_LIBRARYFEATURES_HAS_CPP98_BINDERS_API   1
 
#define BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME   bsls_libraryfeatures_CPP11_ABI
 

Variables

const char * BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME
 

Detailed Description

Outline

Purpose

Provide macros to identify native standard library features.

Classes

Macros

See also
bsls_platform, bsls_compilerfeatures

Description

This component provides a suite of preprocessor macros that indicate the availability of library-specific support of features that may not be available in all standard library versions in use across an organization. None of these macros will be defined unless the compiler is building with a tool-chain targeting at least experimental support for a more recent standard than C++03. For example, the C++11 standard library introduced several functions and types that were not available in libraries for earlier standards. The macro BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY can be used to conditionally compile BDE code depending on those functions when they are available, and exclude that code when those functions are not present, thereby allowing compilation by earlier tool-chains.

The standard library version described by these macros always corresponds to that used to build this component and is the source of the symbols found in the std namespace.

Guarding Against Mixing C++ Versions

This component defines a "link-coercion" symbol that prevents linking a translation unit (that includes this header, possibly indirectly) built against one version of the C++ Standard with a translation unit (also including this header) built against another version of the Standard. For example, attempting to link objects built with C++14 with those built with C++17 will result in a link-time failure. Because BDE supports a variety of features that are enabled depending on the C++ version for which code is built, it is generally not safe to link code built with one version of C++ with code built with another version. For example, in C++11 there are move constructor signatures, whereas in C++03 there are not, and linking code that views the set of constructors for a type differently is an ODR violation. The link-coercion symbol that enforces this is meant to provide users a single, easy-to-comprehend link-time error, rather than having bugs potentially manifest at runtime in ways that are difficult to diagnose.

Converse Logic Is Not Symmetric

The macros defined by this component describe features empirically observed in typical platform/compiler/library combinations used in BDE distributions. The definition of any of these macros implies that a resource is available, however, the converse is not guaranteed. If a macro is not defined, the associated resource may or may not exist in the library. For example, the resource may exist but may be of too early an implementation to be of use to clients of BDE, so in that case the associated macro would not be defined.

BSLS_LIBRARYFEATURES_HAS_C90_GETS

The BSLS_LIBRARYFEATURES_HAS_C90_GETS macro is defined if the gets function (defined in <cstdio>) is provided in namespace std by the native standard library. This dangerous function is removed from the C++14 standard library, and its use with earlier dialects is strongly discouraged.

BSLS_LIBRARYFEATURES_HAS_C99_FP_CLASSIFY

The BSLS_LIBRARYFEATURES_HAS_C99_FP_CLASSIFY macro is defined if all of the listed floating-point classification functions, defined in the headers named below, are implemented by the native standard library in namespace std:

BSLS_LIBRARYFEATURES_HAS_C99_LIBRARY

The BSLS_LIBRARYFEATURES_HAS_C99_LIBRARY macro is defined if all of the listed functions and types, defined in the headers named below, are implemented by the native standard library in namespace std:

This macro is defined first for the following compiler versions:

Notice that the above list does not include snprintf as that is included in the separate BSLS_LIBRARYFEATURES_HAS_C99_SNPRINTF macro. Also note that AIX and Solaris compilers generally have implementations of these functions in the global namespace when including the corresponding C header, but do not provide the standard C++ mapping.

BSLS_LIBRARYFEATURES_HAS_C99_SNPRINTF

The BSLS_LIBRARYFEATURES_HAS_C99_SNPRINTF macro is defined if snprintf function (defined in <cstdio>) is implemented by the native standard library in namespace std.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR

The BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR macro is defined if the auto_ptr class template (defined in <memory>) is provided by the native standard library. This macro is expected to be defined for all libraries/platforms at least until the introduction of C++17 to our build systems.

BSLS_LIBRARYFEATURES_HAS_CPP98_BINDERS_API

The BSLS_LIBRARYFEATURES_HAS_CPP98_BINDERS_API macro is defined if the result_type, argument_type, first_argument_type and second_argument_type typedefs (defined in <functional>) are provided by the native standard library. This macro is expected to be defined for all libraries/platforms at least until the introduction of C++20 to our build systems.

BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY

The BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY macro is used to identify whether the current platform's standard library supports a baseline set of C++11 library features (which are defined below). This is especially important in BSL when importing standard library functions and types into the bsl:: namespace, as is done in bsl+bslhdrs. In particular this macro is used where C++11 has introduced new functions and types into headers available in older versions of the C++ standard. For example, C++11 introduced the type move_iterator to the existing <iterator> header, so bsl_iterator.h uses this macro to determine whether to import std::move_iterator into the bsl namespace.

This macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

Notice that the above list does not include random_shuffle as that is deprecated in C++14 and will be removed in C++17.

BSLS_LIBRARYFEATURES_HAS_CPP14_BASELINE_LIBRARY

The BSLS_LIBRARYFEATURES_HAS_CPP14_BASELINE_LIBRARY macro is used to identify whether the current platform's standard library supports a baseline set of C++14 library features (which are defined below). This is especially important in BSL when importing standard library functions and types into the bsl:: namespace, as is done in bsl+bslhdrs.

This macro is defined if all of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP14_INTEGER_SEQUENCE

The BSLS_LIBRARYFEATURES_HAS_CPP14_INTEGER_SEQUENCE macro is defined if all of the listed conditions are true:

Note that though struct integer_sequence was introduced in the C++14 standard, bsl::integer_sequence is supported by BDE when compiling in C++11 mode.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_BASELINE_LIBRARY

This macro is used to identify whether the current platform's standard library supports a baseline set of C++17 library features (which are defined below). This is especially important in BSL when importing standard library functions and types into the bsl:: namespace, as is done in bsl+bslhdrs.

This macro is defined if all of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP20_BASELINE_LIBRARY

This macro is used to identify whether the current platform's standard library supports a baseline set of C++20 library features (which are defined below). This is especially important in BSL when importing standard library functions and types into the bsl:: namespace, as is done in bsl+bslhdrs.

This macro is defined if all of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_EXCEPTION_HANDLING

The BSLS_LIBRARYFEATURES_HAS_CPP11_EXCEPTION_HANDLING macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_GARBAGE_COLLECTION_API

The BSLS_LIBRARYFEATURES_HAS_CPP11_GARBAGE_COLLECTION_API macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_MISCELLANEOUS_UTILITIES

The BSLS_LIBRARYFEATURES_HAS_CPP11_MISCELLANEOUS_UTILITIES macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

Notice that the function get_unexpected will be removed in C++17.

BSLS_LIBRARYFEATURES_HAS_CPP11_PAIR_PIECEWISE_CONSTRUCTOR

The BSLS_LIBRARYFEATURES_HAS_CPP11_PAIR_PIECEWISE_CONSTRUCTOR macro is defined if the pair class template (defined in <utility>) provided by the native library has a constructor with the signature:

template <class... Args1, class... Args2>
pair(piecewise_construct_t ,
tuple<Args1...> first_args,
tuple<Args2...> second_args);

Notice that the existence of the above constructor implies that each of the following conditions are also true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_PRECISE_BITWIDTH_ATOMICS

The BSLS_LIBRARYFEATURES_HAS_CPP17_PRECISE_BITWIDTH_ATOMICS macro is defined if both of the listed conditions are true: defined if the <atomic> header provided by the native standard library provides type aliases for all of the following precise bit-width atomic types:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_SEARCH_FUNCTORS

The BSLS_LIBRARYFEATURES_HAS_CPP17_SEARCH_FUNCTORS macro is defined if the native library supplies the following class templates in <functional>:

Currently the following compilers define this function template in C++17 or later modes:

BSLS_LIBRARYFEATURES_HAS_CPP17_SEARCH_OVERLOAD

The BSLS_LIBRARYFEATURES_HAS_CPP17_SEARCH_OVERLOAD macro is defined if <algorithm> defines an overload for the search function template that accepts instances of the searcher classes introduced in C++17. See [alg.search]:

template<class ForwardIterator, class Searcher>
constexpr ForwardIterator std::search(ForwardIterator first,
ForwardIterator last,
const Searcher& searcher);

Currently the following compilers define this function template in C++17 or later modes:

BSLS_LIBRARYFEATURES_HAS_CPP17_DEPRECATED_REMOVED

The BSLS_LIBRARYFEATURES_HAS_CPP17_DEPRECATED_REMOVED macro is defined for libraries that do not export names removed in C++17, such as std::ptr_fun. BSLS_LIBRARYFEATURES_HAS_CPP17_DEPRECATED_REMOVED is generally the negation of BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR. Although the removal of deprecated C++17 types is conceptually equivalent to __cplusplus >= 201703L, standard library implementations often provide configuration flags to expose the deprecated library features.

BSLS_LIBRARYFEATURES_HAS_CPP20_DEPRECATED_REMOVED

The BSLS_LIBRARYFEATURES_HAS_CPP20_DEPRECATED_REMOVED macro is defined for libraries that do not export names removed in C++20, such as std::uncaught_exception. Although the removal of deprecated C++20 types is conceptually equivalent to __cplusplus >= 202002L, some standard library implementations may continue to expose the features, and some may provide configuration flags to expose the deprecated library features.

BSLS_LIBRARYFEATURES_HAS_CPP11_PROGRAM_TERMINATION

The BSLS_LIBRARYFEATURES_HAS_CPP11_PROGRAM_TERMINATION macro is defined if of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_RANGE_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP11_RANGE_FUNCTIONS is defined if the following functions are provided by the native standard library in the <iterator> header:

template <class C> auto begin(C& c) -> decltype(c.begin());
template <class C> auto begin(const C& c) -> decltype(c.begin());
template <class C> auto end(C& c) -> decltype(c.end());
template <class C> auto end(const C& c) -> decltype(c.end());
template <class T, size_t N> T* begin(T (&array)[N]);
template <class T, size_t N> T* end(T (&array)[N]);

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP14_RANGE_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP14_RANGE_FUNCTIONS macro is defined if the following functions are provided by the native standard library in the <iterator> header:

template <class C> auto cbegin(const C& c) -> decltype(std::begin(c));
template <class C> auto cend( const C& c) -> decltype(std::end(c));
template <class C> auto rbegin( C& c) -> decltype(c.rbegin());
template <class C> auto rbegin(const C& c) -> decltype(c.rbegin());
template <class C> auto rend( C& c) -> decltype(c.rend());
template <class C> auto rend(const C& c) -> decltype(c.rend());
template <class T, size_t N> reverse_iterator<T*> rbegin(T (&array)[N]);
template <class T, size_t N> reverse_iterator<T*> rend( T (&array)[N]);
template <class E> reverse_iterator<const E*> rbegin(initializer_list<E>);
template <class E> reverse_iterator<const E*> rend( initializer_list<E>);
template <class C> auto crbegin(const C& c) -> decltype(std::rbegin(c));
template <class C> auto crend( const C& c) -> decltype(std::rend(c));

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_STREAM_MOVE

The BSLS_LIBRARYFEATURES_HAS_CPP11_STREAM_MOVE is defined if the standard stream classes (basic_istream , basic_ostream , basic_stream ) all have the C++11 mandated move operations (constructor and assignment operator) defined. Notice that the this macro is separate from the macro BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY as standard library implementations exist that implement almost all of C++11 (which is detected by the BSLS_LIBRARYFEATURES_HAS_CPP11_BASELINE_LIBRARY macro) but not this feature. Note that when BSLS_LIBRARYFEATURES_HAS_CPP11_STREAM_MOVE is defined BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES will also be defined, as the standard feature cannot be implemented without rvalue reference support from the compiler.

BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE

The BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP11_UNIQUE_PTR

The BSLS_LIBRARYFEATURES_HAS_CPP11_UNIQUE_PTR macro is defined if both of the listed conditions are true:

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_BOOL_CONSTANT: !NOT DEFINED!

The BSLS_LIBRARYFEATURES_HAS_CPP17_BOOL_CONSTANT macro is never defined and is mentioned in this component as documentation until its appearance in several BDE test drivers is removed.

The BSLS_LIBRARYFEATURES_HAS_CPP17_BOOL_CONSTANT macro was intended to indicate whether or not the bool_constant alias template (defined in <type_traits>) is provided by the native standard library. It has since been discovered that, as bsl::integral_constant is actually a distinct class template derived from std::integral_constant, there must always be a distinct bsl alias template, which will be provided in a future BDE release. Given this new direction, the need for a macro for the native type is obviated so BSLS_LIBRARYFEATURES_HAS_CPP17_BOOL_CONSTANT is being removed.

BSLS_LIBRARYFEATURES_HAS_CPP17_RANGE_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP17_RANGE_FUNCTIONS macro is defined if the following functions are provided by the native standard library in the <iterator> header:

template <class C> auto empty(const C& c) -> decltype(c.empty());
template <class C> auto data( const C& c) -> decltype(c.data());
template <class C> auto size( const C& c) -> decltype(c.size());

BSLS_LIBRARYFEATURES_HAS_CPP17_ALIGNED_ALLOC

The BSLS_LIBRARYFEATURES_HAS_CPP17_ALIGNED_ALLOC macro is defined if the native standard library provides std::aligned_alloc.

Both libstdc++ and libc++ will provide this call if the underlying C library provides the global call '::aligned_alloc. This call is available on RedHat version 7, for example, but not on RedHat 6. Microsoft does not provide this call. See https://github.com/microsoft/STL/issues/2176

BSLS_LIBRARYFEATURES_HAS_CPP17_TIMESPEC_GET

The BSLS_LIBRARYFEATURES_HAS_CPP17_TIMESPEC_GET macro is defined if the native standard library provides std::timespec_get.

Both libstdc++ and libc++ will provide this call if the underlying C library provides the global call '::timespec_get. This call is available on RedHat version 7, for example, but not on RedHat 6.

BSLS_LIBRARYFEATURES_HAS_CPP17_SPECIAL_MATH_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP17_SPECIAL_MATH_FUNCTIONS is defined if the special math functions such as std::assoc_laguerre, std::beta and others are provided by the native standard library in the <cmath> header.

BSLS_LIBRARYFEATURES_HAS_CPP17_INT_CHARCONV

The BSLS_LIBRARYFEATURES_HAS_CPP17_INT_CHARCONV macro is defined if the native standard library provides the <charconv> header and implements both std::from_chars and std::to_chars for all standard signed and unsigned integer types and the char type, as well as the std::to_chars_result and std::from_chars_result types.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_CHARCONV

The BSLS_LIBRARYFEATURES_HAS_CPP17_CHARCONV macro is defined if the native standard library provides the <charconv> header and implements all required content with no major issues. This macro is defined in addition to the BSLS_LIBRARYFEATURES_HAS_CPP17_INT_CHARCONV macro when the native standard library also implements the std::chars_format enumeration, and both std::from_chars and std::to_chars functions for all 3 standard floating point types (float, double, long double).

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_FILESYSTEM

The BSLS_LIBRARYFEATURES_HAS_CPP17_FILESYSTEM macro is defined if the native standard library provides the <filesystem> header and implements all required content with no major issues.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_PMR

The BSLS_LIBRARYFEATURES_HAS_CPP17_PMR macro is defined if the native standard library provides the <memory_resource> header and implements all required content with no major issues.

This macro is defined first for the following stdlib versions:

BSLS_LIBRARYFEATURES_HAS_CPP17_PMR_STRING

The BSLS_LIBRARYFEATURES_HAS_CPP17_PMR_STRING macro is defined if the native standard library provides the pmr::basic_string class template with no major issues.

Usually pmr::string is available if the PMR feature is available. But GNU libstdc++ doesn't provide it for the obsolete pre-C++11 CoW string implemetation (_GLIBCXX_USE_CXX11_ABI == 0).

BSLS_LIBRARYFEATURES_HAS_CPP20_VERSION

The BSLS_LIBRARYFEATURES_HAS_CPP20_VERSION macro is defined if the native standard library provides the <version> header and implements all required content with no major issues.

A new header, <version>, that defines library feature-test macros has been added in C++20. For better compatibility with the standard library BSLS_LIBRARYFEATURES macros should be based on the standard feature test macro when it is appropriate. See the "STANDARD FEATURE-DETECTION MACROS" section below.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS

The BSLS_LIBRARYFEATURES_HAS_CPP20_CONCEPTS macro is defined if the native standard library provides the <concepts> header and implements all required content with no major issues.

This macro is defined if the standard __cpp_lib_concepts feature-test macro is defined and __cpp_lib_concepts >= 202002L.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES

The BSLS_LIBRARYFEATURES_HAS_CPP20_RANGES macro is defined if the native standard library provides the <ranges> header and implements all required C++20 content with no major issues.

This macro is defined if the standard __cpp_lib_ranges feature-test macro is defined and __cpp_lib_ranges >= 202110L.

This macro is defined first for the following compiler versions:

Note that GCC 11 ranges support is incomplete, as it is missing a number of key Defect Report fixes, notably P2259R1, P2210R2, P2432R1, and P2415R2, the latter being a breaking change between GCC 11 and GCC 12.

BSLS_LIBRARYFEATURES_HAS_CPP20_SOURCE_LOCATION

The BSLS_LIBRARYFEATURES_HAS_CPP20_SOURCE_LOCATION macro is defined if the native standard library provides the <source_location> header and implements all required C++20 content with no major issues.

This macro is defined if the standard __cpp_lib_source_location feature-test macro is defined and __cpp_lib_source_location >= 201907L.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_REF

The BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_REF macro is defined if the bsl::atomic_ref type is available with C++20 semantics.

This macro is defined if the standard __cpp_lib_atomic_ref feature-test macro is defined and __cpp_lib_atomic_ref >= 201806L.

This macro is defined first for the following compiler versions:

(no curent version of libc++ supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_LOCK_FREE_TYPE_ALIASES

The BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_LOCK_FREE_TYPE_ALIASES macro is defined if bsl::atomic_signed_lock_free and bsl:atomic_unsigned_lock_free types are available with C++20 semantics.

This macro is defined if the standard __cpp_lib_atomic_lock_free_type_aliases feature-test macro is defined.

This macro is defined first for the following compiler versions:

(no curent version of clang supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_WAIT_FREE_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_WAIT_FREE_FUNCTIONS is defined if the following free functions are available: bsl::atomic_flag_wait, bsl::atomic_flag_wait_explicit, bsl::atomic_flag_notify_one, bsl::atomic_flag_notify_all with C++20 semantics.

This macro is defined if the standard __cpp_lib_atomic_wait feature-test macro is defined and has a value of at least 201907L.

This macro is defined first for the following compiler versions:

(no current version of GCC supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_FLAG_TEST_FREE_FUNCTIONS

The BSLS_LIBRARYFEATURES_HAS_CPP20_ATOMIC_FLAG_TEST_FREE_FUNCTIONS is defined if the bsl::atomic_flag_test and bsl::atomic_flag_test_explicit functions are available with C++20 semantics.

This macro is defined if the standard __cpp_lib_atomic_flag_test feature-test macro is defined and has a value of at least 201907L.

This macro is defined first for the following compiler versions:

(no current version of GCC supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_MAKE_UNIQUE_FOR_OVERWRITE

The BSLS_LIBRARYFEATURES_HAS_CPP20_MAKE_UNIQUE_FOR_OVERWRITE macro is defined if the bsl::make_unique_for_overwrite function is available with C++20 semantics.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_HAS_CPP20_CALENDAR

The BSLS_LIBRARYFEATURES_HAS_CPP20_CALENDAR is defined if the C++20 Calendar/TZ feature is available in bsl::chrono namespace.

This macro is defined if the standard __cpp_lib_chrono feature-test macro has at least 201907L value.

This macro is defined first for the following compiler versions:

(no current version of GCC or clang supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_CHAR8_MB_CONV

The BSLS_LIBRARYFEATURES_HAS_CPP20_CHAR8_MB_CONV macro is defined if the bsl::mbrtoc8 and bsl::c8rtomb functions are available with C++20 semantics.

(no current version of GCC, clang or MSVC supports this feature

BSLS_LIBRARYFEATURES_HAS_CPP20_IS_LAYOUT_COMPATIBLE

The BSLS_LIBRARYFEATURES_HAS_CPP20_IS_LAYOUT_COMPATIBLE is defined if the bsl::is_layout_compatible meta function is available.

Note that the standard feature test macro __cpp_lib_is_layout_compatible is also defined and has a value of at least 201907L.

This macro is defined first for the following compiler versions:

(no current version of clang supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_IS_CORRESPONDING_MEMBER

The BSLS_LIBRARYFEATURES_HAS_CPP20_IS_CORRESPONDING_MEMBER is defined if the bsl::is_corresponding_member meta function is available.

Note that the standard feature test macro __cpp_lib_is_layout_compatible, the macro that informs BSLS_LIBRARYFEATURES_HAS_CPP20_IS_LAYOUT_COMPATIBLE, is also defined. See the last sentence of P0466R5.

This macro is defined first for the following compiler versions:

(no current version of clang supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_IS_POINTER_INTERCONVERTIBLE

The BSLS_LIBRARYFEATURES_HAS_CPP20_IS_POINTER_INTERCONVERTIBLE is defined if the bsl::is_pointer_interconvertible_base_of and bsl::is_pointer_interconvertible_with_class meta functions are available.

Note that the standard feature test macro __cpp_lib_is_pointer_interconvertible is also defined and has a value of at least 201907L.

This macro is defined first for the following compiler versions:

(no current version of clang supports this feature)

BSLS_LIBRARYFEATURES_HAS_CPP20_JTHREAD

The BSLS_LIBRARYFEATURES_HAS_CPP20_JTHREAD is defined if the C++20 bsl::jthread class in the <bsl_thread.h> header available.

Note that the standard feature test macro __cpp_lib_jthread is also defined and has a value of at least 201911L.

This macro is defined first for the following compiler versions:

BSLS_LIBRARYFEATURES_STDCPP_GNU

The BSLS_LIBRARYFEATURES_STDCPP_GNU macro is defined if the C++ standard library implementation is GNU libstdc++.

BSLS_LIBRARYFEATURES_STDCPP_IBM

The BSLS_LIBRARYFEATURES_STDCPP_IBM macro is defined if the C++ standard library implementation is IBM's VACPP.

BSLS_LIBRARYFEATURES_STDCPP_INTELLISENSE

The BSLS_LIBRARYFEATURES_STDCPP_INTELLISENSE macro is defined if Microsoft's Intellisense is running (instead of a production compiler). Note that detecting Intellisense does not mean that the MSVC compiler is used. Visual Studio 2017 is capable of cross platform development using clang and Visual Studio Code (also featuring Intellisense) may be used with virtually any compiler.

BSLS_LIBRARYFEATURES_STDCPP_LLVM

The BSLS_LIBRARYFEATURES_STDCPP_LLVM_LIBCPP macro is defined if the C++ standard library implementation is LLVM's libc++.

BSLS_LIBRARYFEATURES_STDCPP_MSVC

The BSLS_LIBRARYFEATURES_STDCPP_MSVC macro is defined if the C++ standard library implementation is Microsoft's (Dinkumware based) implementation.

BSLS_LIBRARYFEATURES_STDCPP_LIBCSTD

The BSLS_LIBRARYFEATURES_STDCPP_LIBCSTD macro is defined if the C++ standard library implementation is a RogueWave implementation.

BSLS_LIBRARYFEATURES_STDCPP_STLPORT

The BSLS_LIBRARYFEATURES_STDCPP_STLPORT macro is defined if the C++ standard library implementation is an STLPort implementation.

Usage

In this section we show intended usage of this component.

Example 1: Managing Library-Dependent Interfaces

When building software across multiple platforms a programmer may have to deal with different versions of the native standard library, some providing features that the others do not. The macros defined in this component can be used make features visible only if the required native standard library features are present.

For example, the tuple-type is not available in older versions of the native standard library. Suppose we have a utility component that returns an instance of a tuple of values if the underlying version of the standard library provides that type, and yet remain compilable otherwise.

First, we conditionally include the header file we will need if we define an interface that returns a std::tuple.

#if defined(BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE)
#ifndef INCLUDED_TUPLE
#include <tuple>
#define INCLUDED_TUPLE
#endif
#endif // BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE

Then, we declare the methods that will be unconditionally provided by our utility component:

struct MyStatisticalUtil
{
static double mean(const int *begin, const int *end);
static int median(const int *begin, const int *end);
static double variance(const int *begin, const int *end);
// Return the median (mean, variance) of the sequence of values in
// the specified non-empty, semi-open range '[begin, end)'. The
// behavior is undefined unless 'begin < end'.

Now, we conditionally define an interface that returns a bsl::type, if that type is available. Note that, if all three values are needed, calling this interface is more efficient than calling the earlier three individually because the input need be traversed one time, not three.

#ifdef BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE
static std::tuple<int, double, double> getMedianMeanVariance(
const int *begin,
const int *end);
// Return the median, mean, and variance (in that order) of the
// sequence of values in the specified non-empty, semi-open range
// '[begin, end)'. The behavior is undefined unless 'begin < end'.
#endif // BSLS_LIBRARYFEATURES_HAS_CPP11_TUPLE
};

Finally, we find that our code compiles when we build our code against versions of the native standard library that provide a tuple type, and those that do not. Of course, in the later case the interface that returns

Macro Definition Documentation

◆ BSLS_LIBRARYFEATURES_DETECTION_IN_PROGRESS

#define BSLS_LIBRARYFEATURES_DETECTION_IN_PROGRESS

◆ BSLS_LIBRARYFEATURES_HAS_C90_GETS

#define BSLS_LIBRARYFEATURES_HAS_C90_GETS   1

Set unconditionally for compilers supporting an earlier standard than C++14; this feature macro will be undefined for those platforms with partial support for C++14, implementing the removal of this dangerous function.

◆ BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR

#define BSLS_LIBRARYFEATURES_HAS_CPP98_AUTO_PTR   1

Set unconditionally. This features is found on each compiler version/platform combination tested. Assume universally available until the day tool chains start removing this deprecated class template.

◆ BSLS_LIBRARYFEATURES_HAS_CPP98_BINDERS_API

#define BSLS_LIBRARYFEATURES_HAS_CPP98_BINDERS_API   1

These APIs should be removed in C++20. Undefined conditionally later in this file for implementations that still have it.

◆ BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME

#define BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME   bsls_libraryfeatures_CPP11_ABI

Variable Documentation

◆ BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME

const char* BSLS_LIBRARYFEATURES_LINKER_CHECK_NAME
extern