std::source_location

 

C++

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Technical Specifications

 

Utilities library

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Formatting library (C++20)
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source_location (C++20)
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chars_format (C++17)
Type operations
declval (C++11)
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launder (C++17)

 

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 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 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 [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)

Example

Run this code

#include <iostream>
#include <string_view>
#include <source_location>
 
void log(std::string_view message,
         const std::source_location& location = std::source_location::current())
{
    std::cout << "info:"
              << location.file_name() << ":"
              << location.line() << " "
              << message << '\n';
}
 
int main()
{
    log("Hello world!");
}

Possible output:

info:main.cpp:15 Hello world!