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std::source_location(3)	      C++ Standard Libary      std::source_location(3)

NAME
       std::source_location - std::source_location

Synopsis
	  Defined in header <source_location>
	  struct source_location;	       (since C++20)

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

	  source_location meets	the  DefaultConstructible,  CopyConstructible,
       CopyAssignable
	  and  Destructible  requirements. Lvalue of source_location meets the
       Swappable
	  requirement. 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 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 source_location are trivial and/or constexpr.

Member functions
		Creation
	  constructor	constructs a new source_location with  implementation-
       defined values
			(public	member function)
	  current	 constructs a new source_location corresponding	to the
       location	of the
	  [static]	call site
			(public	static member function)
		Field access
	  line		return the line	number represented by this object
			(public	member function)
	  column	return the column number represented by	this object
			(public	member function)
	  file_name	return the file	name represented by this object
			(public	member function)
	  function_name	return the name	of the function	 represented  by  this
       object, if any
			(public	member function)

Notes
	  Feature-test macro: __cpp_lib_source_location

Example
       // Run this code

	#include <iostream>
	#include <string_view>
	#include <source_location>

	void log(const std::string_view	message,
		 const std::source_location location =
		       std::source_location::current())
	{
	    std::cout << "file:	"
		      << location.file_name() << "("
		      << location.line() << ":"
		      << location.column() << ") `"
		      << location.function_name() << "`: "
		      << message << '\n';
	}

	template <typename T> void fun(T x)
	{
	    log(x);
	}

	int main(int, char*[])
	{
	    log("Hello world!");
	    fun("Hello C++20!");
	}

Possible output:
	file: main.cpp(23:8) `int main(int, char**)`: Hello world!
	file:  main.cpp(18:8)  `void  fun(T)  [with  T	= const	char*]`: Hello
       C++20!

See also
	  stacktrace_entry representation of an	evaluation in a	stacktrace
	  (C++23)	   (class)
	  Filename and line information

http://cppreference.com		  2022.07.31	       std::source_location(3)

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