std::source_location

 

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std::source_location

Member functions

Creation

source_location::source_location

source_location::current

Field access

source_location::line

source_location::column

source_location::file_name

source_location::function_name

 

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

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

Creation
(constructor)	constructs a new source_location with implementation-defined values (public member function)
current [static]	constructs a new source_location corresponding to the location of the 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	Value	Std	Feature
__cpp_lib_source_location	201907L	(C++20)	Source-code information capture (std::source_location)

Example

Run this code

#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!");
}

Possible output:

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

#line	changes the source code's line number and, optionally, the current file name (preprocessing directive)
stacktrace_entry (C++23)	representation of an evaluation in a stacktrace (class)