std:: source_location

The std::source_location class represents certain information about the source code, such as file names, line numbers, and function names. Previously, functions that desire to obtain this information about the call site (for logging, testing, or debugging purposes) must use macros so that predefined macros like __LINE__ and __FILE__ are expanded in the context of the caller. The std::source_location class provides a better alternative.

std::source_location meets the DefaultConstructible , CopyConstructible , CopyAssignable , Destructible and Swappable requirements.

Additionally, the following conditions are true :

• std:: is_nothrow_move_constructible_v < std :: source_location > ,
• std:: is_nothrow_move_assignable_v < std :: source_location > , and
• std:: is_nothrow_swappable_v < std :: source_location > .

It is intended that std::source_location has a small size and can be copied efficiently.

It is unspecified whether the copy/move constructors and the copy/move assignment operators of std::source_location are trivial and/or constexpr.

Member functions

Notes

Example

#include <iostream>
#include <source_location>
#include <string_view>
 
void log(const std::string_view message,
         const std::source_location location =
               std::source_location::current())
{
    std::clog << "file: "
              << location.file_name() << '('
              << location.line() << ':'
              << location.column() << ") `"
              << location.function_name() << "`: "
              << message << '\n';
}
 
template<typename T>
void fun(T x)
{
    log(x); // line 20
}
 
int main(int, char*[])
{
    log("Hello world!"); // line 25
    fun("Hello C++20!");
}

file: main.cpp(25:8) `int main(int, char**)`: Hello world!
file: main.cpp(20:8) `void fun(T) [with T = const char*]`: Hello C++20!

See also