features.hpp

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/*
 * SPDX-FileCopyrightText: © 2025 Larry Chips <larry@larrychips.net>
 * SPDX-Licence-Identifier: MIT
 */
#ifndef UGMISC_FEATURES_HPP
#define UGMISC_FEATURES_HPP

 
#ifdef UGMISC_DOCS
#error "UGMISC_DOCS must be defined for documenting, not compiling."
#endif
 
#ifdef UGMISC_DOCS
#define UGMISC_PREDEFS_HEADER "quoted_header_name"
#endif
#ifdef UGMISC_PREDEFS_HEADER
# include UGMISC_PREDEFS_HEADER
#endif
 
 
 
 
/*
 * I don't want to remember the proper version number everywhere.
 */
 
#if __cplusplus >= 202002L
# define UGMISC_CXX_20 __cplusplus
#else
# undef UGMISC_CXX_20
#endif
 
#if __cplusplus < 201703L
# error "features.hpp doesn't bother to work with less than C++17."
#endif
 
#ifdef UGMISC_DOCS
#define UGMISC_HAVE_VERSION
#endif
#ifdef __has_include
# if __has_include(<version>)
#  include <version>
# endif
#elif defined(UGMISC_HAVE_VERSION)
# include <version>
#endif
 
#ifdef __has_include
# define UGMISC_HAS_INCLUDE_OR_IGNORE(...) __has_include(__VA_ARGS__)
#else
# define UGMISC_HAS_INCLUDE_OR_IGNORE(...)
#endif
 
 
 
 
#ifndef UGMISC_DOCS
/*
 * These exist for documentation purposes.
 * See doc/default_Doxyfile.in: PREDEFINED.
 *
 * They allow the feature flags to be defined as true or false at compile time,
 * but as "compiler and library dependent" in the documentation.
 */
#define UGMISC_FEATURE_TRUE true
#define UGMISC_FEATURE_FALSE false
#endif
 
 
 
namespace ugmisc {
 
 
 

 
struct Features {
    /*
     * Language features.
     */
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_CONSTEXPR_DESTRUCTORS
# define UGMISC_NO_CONSTEXPR_DESTRUCTORS
#endif
#if defined(UGMISC_HAVE_CONSTEXPR_DESTRUCTORS) && defined(UGMISC_NO_CONSTEXPR_DESTRUCTORS)
# error "Predefines include HAVE_CONSTEXPR_DESTRUCTORS and NO_CONSTEXPR_DESTRUCTORS."
#endif
#if !defined(UGMISC_HAVE_CONSTEXPR_DESTRUCTORS) && !defined(UGMISC_NO_CONSTEXPR_DESTRUCTORS)
# ifdef UGMISC_CXX_20
#  define UGMISC_HAVE_CONSTEXPR_DESTRUCTORS
# else
#  undef UGMISC_HAVE_CONSTEXPR_DESTRUCTORS
# endif
#endif
#ifdef UGMISC_HAVE_CONSTEXPR_DESTRUCTORS
    static constexpr bool constexpr_destructors = UGMISC_FEATURE_TRUE;
#else
    static constexpr bool constexpr_destructors = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_CONCEPTS
#endif
#if __cpp_concepts
# define UGMISC_HAVE_CONCEPTS
    static constexpr bool concepts = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_CONCEPTS
    static constexpr bool concepts = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_CONDITIONAL_TRIVIALS
#endif
#if __cpp_concepts >= 202002L
# define UGMISC_HAVE_CONDITIONAL_TRIVIALS
    static constexpr bool conditional_trivials = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_CONDITIONAL_TRIVIALS
    static constexpr bool conditional_trivials = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_CONSTEVAL
#endif
#if __cpp_consteval
# define UGMISC_HAVE_CONSTEVAL
    static constexpr bool consteval_functions = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_CONSTEVAL
    static constexpr bool consteval_functions = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#if UGMISC_DOCS
# define UGMISC_HAVE_CONSTEVAL_IF
#endif
#if __cpp_consteval >= 202211L
# define UGMISC_HAVE_CONSTEVAL_IF
    static constexpr bool consteval_if = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_CONSTEVAL_IF
    static constexpr bool consteval_if = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
    /*
     * Library features.
     */
 
 
 
 
#if UGMISC_DOCS
# define UGMISC_HAVE_BIT_CAST
#endif
#if __cpp_lib_bit_cast
# define UGMISC_HAVE_BIT_CAST
    static constexpr bool bit_cast = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_BIT_CAST
    static constexpr bool bit_cast = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#if UGMISC_DOCS
#define UGMISC_HAVE_BITOPS
#endif
#if __cpp_lib_bitops
# define UGMISC_HAVE_BITOPS
    static constexpr bool bitops = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_BITOPS
    static constexpr bool bitops = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_CONSTEXPR_SWAP_ALGORITHMS
#endif
#if __cpp_lib_constexpr_swap_algorithms
# define UGMISC_HAVE_CONSTEXPR_SWAP_ALGORITHMS
    static constexpr bool constexpr_swap_algorithms = UGMISC_FEATURE_TRUE;
#else
# undef UGMISC_HAVE_CONSTEXPR_SWAP_ALGORITHMS
    static constexpr bool constexpr_swap_algorithms = UGMISC_FEATURE_FALSE;
#endif
 
 
 
 
#ifdef UGMISC_DOCS
# define UGMISC_HAVE_UNREACHABLE
#endif
#if __cpp_lib_unreachable
# define UGMISC_HAVE_UNREACHABLE
    static constexpr bool unreachable = UGMISC_FEATURE_TRUE;
#else
    static constexpr bool unreachable = UGMISC_FEATURE_FALSE;
# undef UGMISC_HAVE_UNREACHABLE
#endif
}; // struct Features
 
 
} /* ::ugmisc */
 
 
 
 
#ifdef UGMISC_HAVE_UNREACHABLE
# define UGMISC_unreachable ::std::unreachable
# include <utility>
#else
# define UGMISC_unreachable ::ugmisc::unreachable
namespace ugmisc {
[[noreturn]] inline void unreachable() { }
}
#endif
 
 
 
 
/*
 * This is defined when concepts are supported AND when building documentation.
 * It is used where there are two declarations of a template and one uses
 * concepts.  We document the one with concepts.
 */
#ifdef UGMISC_HAVE_CONCEPTS
# define UGMISC_USE_CONCEPT_DECLS
#else
# undef UGMISC_USE_CONCEPT_DECLS
#endif
 
#endif /* UGMISC_FEATURES_HPP */