std::source_location

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std::source_location
 
Defined in header <source_location>
struct source_location;
 (since 哋它亢++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 and Destructible requirements. Lvalue of std::source_location meets the Swappable requirement.

Additionally, the following conditions are true:

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
constructs a new source_location with implementation-defined values
(public member function)
[static]
 constructs a new source_location corresponding to the location of the call site
(public static member function)
Field access
return the line number represented by this object
(public member function)
return the column number represented by this object
(public member function)
return the file name represented by this object
(public member function)
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 (哋它亢++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 哋它亢++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 哋它亢++20!

See also

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