- Generated by
1.9.8
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BDE 4.14.0 Production release
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Macros | |
| #define | BSLS_COMPILERFEATURES_CPLUSPLUS 199711L |
| #define | BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS 1 |
| #define | BSLS_COMPILERFEATURES_SIMULATE_VARIADIC_TEMPLATES 1 |
| #define | BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES 1 |
| #define | BSLS_COMPILERFEATURES_SIMULATE_FORWARD_WORKAROUND 1 |
| #define | BSLS_COMPILERFEATURES_FORWARD_REF(T) const T& |
| #define | BSLS_COMPILERFEATURES_FORWARD(T, V) ::BloombergLP::bslmf::Util::forward(V) |
Provide macros to identify compiler support for C++11 features.
__cplusplusT to be forwardedV of type T__LINE__ value for multi-linealignas[[fallthrough]][[maybe_unused]][[nodiscard]][[noreturn]] attributeconstexpr specifierconstexpr spec.constexpr spec.decltype= default= deletedenum classextern templatefinal keyword__has_include0x1.5p+5 supportedinline namespaceinline variablesnoexcept operatornoexcept fnctype diffnullptrexplicit operatoroverride keyword<=> operator<type_traits> headerchar(16|32)_tchar8_tThis component provides a suite of preprocessor macros to identify compiler-specific support of language features that may not be available on all compilers in use across an organization. For example, as post-classic (C++11 and beyond) language facilities become more broadly available with sufficient quality (such as extern template) macros will be defined here to indicate whether the current platform/compiler combination supports the corresponding language features. Note that in some cases, support for a given feature may need to be explicitly enabled by using an appropriate compiler command-line option.
This header is a large and complex mesh of fairly unrelated and deep preprocessor conditionals with defining and undefining of many features macros. It is hard for a human to scan this file and understand how and where particular feature macros are set. To make matter more difficult in certain circumstances we also unset/undefine macros. For this reason this header file uses a few special formatting rules to allow faster scanning:
1 (replacement text) of {Binary Macros} may be 79 characters long (plus newline). Line continuation characters in long preprocessor conditionals etc. must be placed onto column 78. This is to allow a human to easily scan the file for places where feature macros are being defined.#if*) and the unusually long feature macro names defined in this header we use 2 spaces indentation to ensure that most preprocessor directives don't wrap (and become hard to read).Binary macros defined in this file (such as the BSLS_COMPILERFEATURES_SUPPORT_* macros, and the BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS, and the BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST macros) that represents a true/false preprocessor value are either undefined or defined to be the integer value 1. This allows the traditional, idiomatic use of these macros where more brief preprocessor conditions rely on the fact that the C and C++ preprocessors replace these unknown tokens with the value 0 in conditions: The following short condition
works identical to the following, longer one.
Note that the line continuation backslash has been replaced with / to silence "multiline comment" warnings.
The following are the macros provided by this component. Note that they are not defined for all platform/compiler combinations.
BSLS_COMPILERFEATURES_CPLUSPLUS This macro provides a portable way to determine the version of the C++ standard mode that is being used. In general, this has the same value as the standard
__cplusplusmacro, but on some compilers with some settings the standard macro does not get assigned the correct value. The values generally set (as defined in the C++ Standard) are the year and month when the Standard was completed, and the value of this macro should be compared with the appropriate constants:
- 199711L – before C++11
- 201103L – C++11
- 201402L – C++14
- 201703L – C++17
- 202002L – C++20
- 202302L – C++23 Note that compilers may report "in-between" values to indicate partial support of a standard, so
BSLS_COMPILERFEATURES_CPLUSPLUS > 201402Lnormally means that some C++17 features are available. Since those values are not standardized their meaning varies.
BSLS_COMPILERFEATURES_FORWARD_REF(T) This macro provides a portable way to declare a function template argument of type
Tthat is to be perfect-forwarded. The expansion of the macro will use syntax that is appropriate for the current compiler settings for this platform.
BSLS_COMPILERFEATURES_FORWARD(T, V) This macro provides a portable way to perfect-forward a function template argument,
V, of typeT. The expansion of the macro will use syntax that is appropriate for the current compiler settings for this platform. Note that due to the vagaries of implementing this macro, client code using this macro should provide the following two inclusions (in addition to the requisite inclusion of this header):
#include <bslmf_util.h>#include <bsls_util.h>
BSLS_COMPILERFEATURES_GUARANTEED_COPY_ELISION This macro is defined if the compiler always elides all copies (or moves) when returning a prvalue expression from a function and using that expression to initialize a class object of the same type (ignoring cv qualifications). Specifically, given the function,
Thing funcReturningThing() { return Thing(ctor-args...); }, the return value is always initialized with(ctor-args...); no copy is performed in the return statement. Additionally,Thing var(funcReturningThing())always constructsvardirectly from the return expression offuncReturningThing(); again, no copies are involved. The semantics of these optimizations are guaranteed in C++17 and later, but are optional in previous versions of C++.
BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONS The
BSLS_COMPILERFEATURES_INITIALIZER_LIST_LEAKS_ON_EXCEPTIONSmacro is defined for implementations that leak temporary objects constructed trying to initialize astd::initializer_listobject in the event that one of the elements of the list throws from its constructor. This is known to affect gcc as recently as the 8.x series, and the Sun CC compiler in C++11 mode. This would often reveal itself as a spurious memory leak in exception-safety tests for initializer_list constructors, so rises to the level of a generally supported defect-detection macro.
BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST The
BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRSTmacro is defined for implementations that implement WG14 N2322 (http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2322.htm) "Recommended practice" on the substitution value for the__LINE__(predefined) preprocessor macro when expanding a macro that uses__LINE__in its body, and that macro invocation spans multiple source lines (logical or physical). When macro is defined__LINE__is substituted with the line number of the first character of the macro name of the (multi-line) macro invocation. When this macro is not defined__LINE__is replaced (as traditional on older C++ compilers) by the line number of the last character of the macro invocation that expands to a use of__LINE__. See also {Example 2:__LINE__Macro Multi-line Value Differences Demonstration}.
BSLS_COMPILERFEATURES_SUPPORT_ALIAS_TEMPLATES This macro is defined if alias templates are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_ALIGNAS This macro is defined if
alignasalignment specifier is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_FALLTHROUGH This macro is defined if the
[[fallthrough]]attribute is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_MAYBE_UNUSED This macro is defined if the
[[maybe_unused]]attribute is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NODISCARD This macro is defined if the
[[nodiscard]]attribute is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_ATTRIBUTE_NORETURN This macro is defined if the
[[noreturn]]attribute is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_CONCEPTS This macro is defined if the concepts core language feature is supported by the current compiler settings for this platform, as defined by ISO C++20.
BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR This macro is defined if
constexpris supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP14 This macro is defined if
constexprwith C++14 semantics is supported by the current compiler settings for this platform. In particular, this allows multiple statements in aconstexprfunction; changing state of local variables within the function; and making non-constmember functionsconstexpr.
BSLS_COMPILERFEATURES_SUPPORT_CONSTEXPR_CPP17 This macro is defined if
constexprwith C++17 semantics is supported by the current compiler settings for this platform. In particular, this allows lambda functions to be defined in aconstexprfunction.
BSLS_COMPILERFEATURES_SUPPORT_COROUTINE This macro is defined if coroutines with C++20 (or later) semantics are supported by the current compiler settings, including the existence of the <coroutine> standard header that provides the basic library facilities necessary to make use of coroutines.
BSLS_COMPILERFEATURES_SUPPORT_CTAD This macro is defined if template argument deduction introduced in the C++17 Standard are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_DECLTYPE This macro is defined if
decltypeis supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_DEFAULT_TEMPLATE_ARGS This macro is defined if default template arguments for function templates are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_DEFAULTED_FUNCTIONS This macro is defined if defaulted functions are supported by the current compiler settings for this platform (i.e., via the
= defaultsyntax).
BSLS_COMPILERFEATURES_SUPPORT_DELETED_FUNCTIONS This macro is defined if deleted functions are supported by the current compiler settings for this platform (i.e., via the
= deletesyntax).
BSLS_COMPILERFEATURES_SUPPORT_ENUM_CLASS This macro is defined if
enum classis supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_EXTERN_TEMPLATE This macro is defined if
extern templateis supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_FINAL This macro is defined if
finalis supported for classes and member functions by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_GENERALIZED_INITIALIZERS This macro is defined if generalized initializers are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_HAS_INCLUDE This macro is defined if
__has_includeis supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_HEXFLOAT_LITERALS This macro is defined if hexadecimal format literals for floating point types are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_INCLUDE_NEXT This macro is defined if include_next is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_INLINE_NAMESPACE This macro is defined if
inlinenamespaces introduced in the C++11 Standard are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES This macro is defined if
inlinevariables introduced in the C++17 Standard are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT This macro is defined if the
noexceptkeyword is supported by the current compiler settings for this platform, both for designating a function as not throwing and for testing if an expression may throw. The definition of this macro does not depend on whether the current compiler configuration has disabled support for exceptions.
BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPE This macro is defined if the
noexceptkeyword is supported by the current compiler settings for this platform such that ifnoexceptis used to designate a function as not throwing, that use ofnoexceptis explicitly considered part of the type of the function (a feature introduced in C++17). The definition of this macro does not depend on whether the current compiler configuration has disabled support for exceptions.
BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_TYPES Deprecated, use
BSLS_COMPILERFEATURES_SUPPORT_NOEXCEPT_IN_FNC_TYPEinstead.
BSLS_COMPILERFEATURES_SUPPORT_NULLPTR This macro is defined if
nullptris supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_OPERATOR_EXPLICIT This macro is defined if the
explicitkeyword applied to conversion operators is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_OVERRIDE This macro is defined if the
overridekeyword is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_RAW_STRINGS This macro is defined if the compiler supports C++-11-style R"tag(string)tag" strings.
BSLS_COMPILERFEATURES_SUPPORT_REF_QUALIFIERS This macro is defined if member functions with trailing reference qualifiers (e.g.,
void myfunc(int) &&) are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES This macro is defined if rvalue references are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_STATIC_ASSERT This macro is defined if static_assert is supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_THREE_WAY_COMPARISON This macro is defined if
<=>operator is supported by the current compiler settings for this platform. Including full library support as of C++20.
BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS This macro is defined if dynamic exception specifications are supported by the current compiler settings for this platform. Dynamic exception specifications were deprecated in C++11, and actively removed from the language in C++17. The definition of this macro does not depend on whether the current compiler configuration has disabled support for exceptions.
BSLS_COMPILERFEATURES_SUPPORT_TRAITS_HEADER This macro is defined if the standard library for the current compiler settings for this platform supports some form of the standard
<type_traits>header. Note that many standard library implementations provided partial support for a long time, and those libraries will be identified as providing the<type_traits>header.
BSLS_COMPILERFEATURES_SUPPORT_UNICODE_CHAR_TYPES This macro is defined if the compiler supports the
char16_tandchar32_ttypes and the related u and U prefixes for character- and string-literal values.
BSLS_COMPILERFEATURES_SUPPORT_USER_DEFINED_LITERALS This macro is defined if user-defined literals are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_UTF8_CHAR_TYPE This macro is defined if the compiler supports the
char8_ttype.
BSLS_COMPILERFEATURES_SUPPORT_VARIADIC_TEMPLATES This macro is defined if variadic template parameters are supported by the current compiler settings for this platform.
BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES This macro is defined if variable templates introduced in the C++14 Standard are supported by the current compiler settings for this platform.
The following code snippets illustrate use of this component.
Suppose that we wish to "preinstantiate" bsl::basic_string for a given character type, say, char, on platforms that support extern template. To accomplish this, we would do the following in the .h and .cpp files of the bslstl_string component:
Note that this isn't an example of use, it is a demonstration of compiler preprocessor behavior and the BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST macro.
Sometimes we write code that uses line numbers for logging or other purposes. Although most of the time the precise values of those line numbers (in program output, such as assertions, or logs) is unimportant (the output is read by humans who are good at finding the line that actually emitted the text), sometimes programs read other programs' output. In such cases the precise values for the line numbers may matter. This example demonstrates the two ways our currently supported C++ compilers generate line numbers in multi-line macro expansion contexts (from the __LINE__ macro), and how the presence (or absence) of the macro BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST indicates which method the current compiler uses. First, we define a macro that uses __LINE__ in its replacement text:
Note that this macro has the function-like syntax so we can easily span its invocation to multiple lines.
Next, we record the current line number in a constant, and also record the line number from our macro, but we span the macro invocation multiple lines to invoke the unspecified behavior.
The two lines must follow each other due to working with line numbering:
We deliberately extended the macro invocation to more than 2 physical source code lines so that we can demonstrate the two distinct behaviors: using the line number of the first character or the last. Extending the number of lines beyond the macro invocation (by placing the semicolon on its own line) has no effect on the line number substitution inside the macro. The dummy argument is required for C++03 compatibility.
If we follow the definition of A_LINE without any intervening empty lines the line number of the first character of the macro invocation will be A_LINE + 1, while the last falls on line A_LINE + 4.
Now we demonstrate the two different behaviors and how the presence of BSLS_COMPILERFEATURES_PP_LINE_IS_ON_FIRST indicates which one will occur:
Finally note that WG14 N2322 defines this behavior as unspecified, therefore it is in the realm of possibilities, although not likely (in C++ compilers) that further, more complicated or even indeterminate behaviors may arise.
This macro is defined if the compiler leaks temporary objects constructed trying to initialize a std::initializer_list object in the event that one of the elements of the list throws from its constructor.
Note that https://en.cppreference.com/w/cpp/compiler_support is a useful reference for initial versions to test for support for various features.
This macro is defined if the compiler substitutes the __LINE__ macro in macro expansions with the line number of the first character of the macro invocation, which is the recommended practice for the C preprocessor (see WG14 N2322 at http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2322.htm). Note that all BDE supported compilers that do not define this macro use the line number of the last character of the macro invocation instead.
This macro is defined if the compiler supports syntax to introduce a typedef-name using alias-declaration syntax, declaring a name for a family of types.
This macro is defined if the compiler supports the alignas alignment specifier.
This feature is not yet supported in Visual Studio, IBM xlC, Oracle CC.
This macro is defined if the compiler supports [[noreturn]] C++11 attribute syntax. MSVC supports the attribute with alternative syntax __declspec(noreturn), earlier versions of GCC and Clang support the alternative syntax __attribute__((noreturn)), and xlC supports the alternative syntax _Noreturn. This macro does not support alternative syntaxes.
This macro is defined if the compiler supports [[nodiscard]] C++17 attribute syntax.
This macro is defined if the compiler supports [[fallthrough]] C++17 attribute syntax.
This macro is defined if the compiler supports [[maybe_unused]] C++17 attribute syntax.
This macro is defined if the concepts core language feature is fully supported, as defined by ISO C++20.
This macro is defined if the standard __cpp_concepts feature-test macro has at least 202002L value.
Note that clang 16.0 still has a bug that prevents it declaring C++20 concepts support. (At the time of writing (2023.Jun.01) clang trunk does not yet declare C++20 concepts to be available, _cpp_concepts is 201907LL).
This macro is defined in the compiler supports the constexpr reserved keyword.
This macro is defined in the compiler supports the constexpr reserved keyword with C++14 semantics.
This macro is defined if the compiler supports the constexpr reserved keyword with C++17 semantics.
This macro is defined if the compiler supports at least the C++20 coroutine core language features and also provides the <coroutine> standard header providing the basic library facilities necessary to make use of coroutines.
This macro is defined if the compiler supports the decltype reserved word.
This macro is defined if the compiler supports syntax to introduce defaulted functions.
This macro is defined if the compiler supports syntax to introduce defaulted functions.
This macro is defined if the compiler supports syntax to introduce deleted functions.
This macro is defined if the compiler supports allowing suppression of implicit instantiation of templates by prefixing an explicit instantiation directive with the extern keyword.
This macro is defined if the compiler supports both finalizing a class using the final keyword after the class name as well as preventing further derived classes from overriding a virtual function by using final after its signature.
This macro is defined if the compiler supports generalized initializers.
This macro is defined if the compiler supports __has_include semantics as defined in the C++17 Standard (see also P006R1). Note that this preprocessor feature is often available in earlier language dialects.
This macro is defined if the compiler supports #include_next.
This macro is defined if the compiler supports inline namespaces introduced in the C++11 Standard.
This macro is defined if the compiler supports inline variables introduced in the C++17 Standard.
This macro is defined if the compiler supports the noexcept reserved keyword.
This macro is defined if the compiler supports the nullptr reserved word.
This macro is defined if the compiler supports use of the explicit keyword to indicate that a conversion operator only available for explicit conversions.
This macro is defined if the compiler supports use of the override keyword to indicate that a member function is meant to override a virtual function (and cause a failure if that is not the case).
This macro is defined if the compiler supports the use of C++11-style R"tag(string)tag" strings.
This macro is defined if member functions with trailing reference qualifiers (e.g., void myfunc(int) &) and rvalue reference qualifiers (e.g., void myFunc(int) &&) are supported. Note that this macro implies that BSLS_COMPILERFEATURES_SUPPORT_RVALUE_REFERENCES is also defined.
This macro is defined if the compiler supports rvalue references and move semantics compatible with the final C++11 specification. (Semantics have changed since early draft proposals.)
This macro is defined if the compiler supports the static_assert reserved word.
This macro is defined if the compiler supports <=> operator.
This macro is defined if the compiler supports the ability to express a template that accepts an arbitrary number of parameters in a type-safe manner.
This macro is defined if the compiler supports variable templates introduced in the C++14 Standard.
Microsoft Visual C++ in Microsoft Visual Studio has many different associated versions:
_MSVC_VER (such as 19.32 and 1932)_MSVC_FULL_VER (such as 193231329)The following table shows the mapping between the different version numbers. The source for the table was https://dev.to/yumetodo/list-of-mscver-and-mscfullver-8nd and the _MSC_VER entry on https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros at 2020-12-13 20:00-05:00 (EST/New York).
(*) Visual Studio may receive interim updates that do not contribute into the Visual Studio "human friendly" version, but are visible in other version numbers.
| #define BSLS_COMPILERFEATURES_CPLUSPLUS 199711L |
| #define BSLS_COMPILERFEATURES_FORWARD | ( | T, | |
| V | |||
| ) | ::BloombergLP::bslmf::Util::forward(V) |
| #define BSLS_COMPILERFEATURES_FORWARD_REF | ( | T | ) | const T& |
| #define BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES 1 |
| #define BSLS_COMPILERFEATURES_SIMULATE_FORWARD_WORKAROUND 1 |
| #define BSLS_COMPILERFEATURES_SIMULATE_VARIADIC_TEMPLATES 1 |
| #define BSLS_COMPILERFEATURES_SUPPORT_THROW_SPECIFICATIONS 1 |
1.9.8