utl::predef
utl::predef module contains macros and constant expressions for detecting compilation details.
It uses known implementation-defined macros to deduce compilation details and abstracts them away behind a unified API.
[!Note] There exists a very similar boost library with the same name, it supports more exotic platforms, but has a different API and doesn’t provide some of the things defined in this module.
Definitions
// Compiler detection
#define UTL_PREDEF_COMPILER_IS_MSVC // only one of these macros will be defined
#define UTL_PREDEF_COMPILER_IS_GCC
#define UTL_PREDEF_COMPILER_IS_CLANG
#define UTL_PREDEF_COMPILER_IS_LLVM
#define UTL_PREDEF_COMPILER_IS_ICC
#define UTL_PREDEF_COMPILER_IS_PGI
#define UTL_PREDEF_COMPILER_IS_IBMCPP
#define UTL_PREDEF_COMPILER_IS_NVCC
#define UTL_PREDEF_COMPILER_IS_UNKNOWN
constexpr std::string_view compiler_name;
constexpr std::string_view compiler_full_name;
// Platform detection
#define UTL_PREDEF_PLATFORM_IS_WINDOWS_X64 // only one of these macros will be defined
#define UTL_PREDEF_PLATFORM_IS_WINDOWS_X32
#define UTL_PREDEF_PLATFORM_IS_CYGWIN
#define UTL_PREDEF_PLATFORM_IS_ANDROID
#define UTL_PREDEF_PLATFORM_IS_LINUX
#define UTL_PREDEF_PLATFORM_IS_UNIX
#define UTL_PREDEF_PLATFORM_IS_MACOS
#define UTL_PREDEF_PLATFORM_IS_UNKNOWN
constexpr std::string_view platform_name;
// Architecture detection
#define UTL_PREDEF_ARCHITECTURE_IS_X86_64 // only one of these macros will be defined
#define UTL_PREDEF_ARCHITECTURE_IS_X86_32
#define UTL_PREDEF_ARCHITECTURE_IS_ARM
#define UTL_PREDEF_ARCHITECTURE_IS_UNKNOWN
constexpr std::string_view architecture_name;
// Language standard detection
#define UTL_PREDEF_STANDARD_IS_23_PLUS // multiple of these macros can be defined
#define UTL_PREDEF_STANDARD_IS_20_PLUS
#define UTL_PREDEF_STANDARD_IS_17_PLUS
#define UTL_PREDEF_STANDARD_IS_14_PLUS
#define UTL_PREDEF_STANDARD_IS_11_PLUS
#define UTL_DEFINE_STANDARD_IS_UNKNOWN
constexpr std::string_view standard_name;
// Compilation mode detection
#define UTL_PREDEF_MODE_IS_DEBUG
constexpr bool debug;
// Optimization macros
#define UTL_PREDEF_FORCE_INLINE
#define UTL_PREDEF_NO_INLINE
#define UTL_PREDEF_ASSUME
[[noreturn]] void unreachable();
// Other utils
std::string compilation_summary();
Methods
Compiler detection
// Compiler detection #define UTL_PREDEF_COMPILER_IS_MSVC #define UTL_PREDEF_COMPILER_IS_GCC #define UTL_PREDEF_COMPILER_IS_CLANG #define UTL_PREDEF_COMPILER_IS_LLVM #define UTL_PREDEF_COMPILER_IS_ICC #define UTL_PREDEF_COMPILER_IS_PGI #define UTL_PREDEF_COMPILER_IS_IBMCPP #define UTL_PREDEF_COMPILER_IS_NVCC #define UTL_PREDEF_COMPILER_IS_UNKNOWN
Only one of these macros will be defined. The macro that gets defined corresponds to the detected compiler. If no other option is suitable, unknown is used as a fallback.
This is useful for compiler-specific conditional compilation.
constexpr std::string_view compiler_name;
constexpr string that evaluates to the abbreviated name of the detected compiler.
Possible values: MSVC, GCC, clang, LLVM, ICC, PGI, IBMCPP, NVCC, <unknown>.
constexpr std::string_view compiler_full_name;
constexpr string that evaluates to the full name of the detected compiler.
Possible values: Microsoft Visual C++ Compiler, GNU C/C++ Compiler, Clang Compiler, LLVM Compiler, Inter C/C++ Compiler, Portland Group C/C++ Compiler, IBM XL C/C++ Compiler, Nvidia Cuda Compiler Driver, <unknown>.
Platform detection
// Platform detection #define UTL_PREDEF_PLATFORM_IS_WINDOWS_X64 #define UTL_PREDEF_PLATFORM_IS_WINDOWS_X32 #define UTL_PREDEF_PLATFORM_IS_CYGWIN #define UTL_PREDEF_PLATFORM_IS_ANDROID #define UTL_PREDEF_PLATFORM_IS_LINUX #define UTL_PREDEF_PLATFORM_IS_UNIX #define UTL_PREDEF_PLATFORM_IS_MACOS #define UTL_PREDEF_PLATFORM_IS_UNKNOWN
Only one of these macros will be defined. The macro that gets defined corresponds to the detected platform. If no other option is suitable, unknown is used as a fallback.
This is useful for platform-specific conditional compilation.
constexpr std::string_view platform_name;
constexpr string that evaluates to the name of the detected platform.
Possible values: Windows64, Windows32, Windows (CYGWIN), Android, Linux, Unix-like OS, MacOS, <unknown>.
Architecture detection
#define UTL_PREDEF_ARCHITECTURE_IS_X86_64 #define UTL_PREDEF_ARCHITECTURE_IS_X86_32 #define UTL_PREDEF_ARCHITECTURE_IS_ARM #define UTL_PREDEF_ARCHITECTURE_IS_UNKNOWN
Only one of these macros will be defined. The macro that gets defined corresponds to the detected CPU architecture. If no other option is suitable, unknown is used as a fallback.
This is useful for architecture-specific conditional compilation.
constexpr std::string_view architecture_name;
constexpr string that evaluates to the name of the detected CPU architecture.
Possible values: x86-64, x86-32, ARM, <unknown>
Language standard detection
#define UTL_PREDEF_STANDARD_IS_23_PLUS #define UTL_PREDEF_STANDARD_IS_20_PLUS #define UTL_PREDEF_STANDARD_IS_17_PLUS #define UTL_PREDEF_STANDARD_IS_14_PLUS #define UTL_PREDEF_STANDARD_IS_11_PLUS #define UTL_DEFINE_STANDARD_IS_UNKNOWN
Multiple of these macros can be defined. Macro that get defined correspond to the available C++ standard. If no other option is suitable, unknown is used as a fallback.
This is useful for conditional compilation based on available standard.
constexpr std::string_view standard_name;
constexpr string that evaluates to the name of the detected C++ standard. Possible values: C++23, C++20, C++17, C++14, C++11, <unknown>.
Note: Considering that this is a C++17 library, there should be no feasible way to get values below C++17, however they are still provided for the sake of implementation completeness, shall the source code be copied directly.
Compilation mode detection
#define UTL_PREDEF_MODE_IS_DEBUG
Defined when compiling in debug mode. Works as an alias for _DEBUG, provided for the sake of feature completeness.
constexpr bool debug;
constexpr bool that evaluates to true when compiling in debug mode.
This is useful for if constexpr conditional compilation of debug code.
Optimization macros
#define UTL_PREDEF_FORCE_INLINE
Hints (MSVC) or forces (GCC, clang and ICX) function inlining using compiler built-ins.
Note: Compiles to nothing if there is no suitable compiler support.
#define UTL_PREDEF_NO_INLINE
Disables function inlining using compiler built-ins.
Note: Compiles to nothing if there is no suitable compiler support.
#define UTL_PREDEF_ASSUME(condition)
Equivalent to C++23 [[assume(condition)]] that supports earlier standards using MSVC and clang built-ins.
Invokes undefined behavior if statement condition evaluates to false, which provides compiler with additional optimization opportunities since implementations may assume that undefined behavior can never happen and the statement always holds.
Note 1: Compiles to nothing if there is no suitable compiler support.
Note 2: In debug mode also works like an assert().
[[noreturn]] void unreachable();
Equivalent to C++23 std::unreachable that supports earlier standards using MSVC, clang and GCC built-ins.
Compiler implementation may use this to optimize impossible code branches away.
Note: Compiles to nothing if there is no suitable compiler support.
Other utils
std::string compilation_summary();
Returns a string containing a detailed summary of compilation details based on the other functionality of this header. See example.
Examples
Conditional compilation
[ Run this code ]
#if defined(UTL_PREDEF_COMPILER_IS_GCC) || defined(UTL_PREDEF_COMPILER_IS_CLANG)
std::cout << "Running Clang or GCC";
#elif defined(UTL_PREDEF_COMPILER_IS_MSVC)
std::cout << "Running MSVC";
#else
std::cout << "Running some other compiler";
#endif
Output:
Running Clang or GCC
Optimization macros
[ Run this code ]
enum class State { YES, NO };
UTL_PREDEF_FORCE_INLINE // tells compiler to always inline the function
std::string to_string(State value) {
switch (value) {
case State::YES: return "YES";
case State::NO : return "NO" ;
default: utl::predef::unreachable();
// tells compiler that 'default' case will never be executed
}
}
Compilation summary
[ Run this code ]
std::cout << utl::predef::compilation_summary();
Output:
Compiler: GNU C/C++ Compiler
Platform: Linux
Architecture: x86-64
Compiled in DEBUG: false
Compiled under OS: true
Compilation date: Dec 1 2024 03:47:20