**`std::source_location`** is a class first introduced in [C++20](https://en.cppreference.com/w/cpp/20) that represents certain information about the source code, such as file names, line numbers, and function names.

> Make sure to include the `source_location` header file.


# Built-in functions

`std::source_location` comes with some basic built-in functions. They are explained below.

## Creation

* **`source_location()`**: Construct a new object of unspecified value.
* **`source_location::current()`**: Static member function, construct a new object that corresponds to the location of the call site.

## Field access

* **`line()`**: Return the line number represented by the object.
* **`column()`**: Return the column number represented by the object.
* **`file_name()`**: Return the file name represented by the object.
* **`function_name()`**: Return the name of the function represented by the object, if any.

# Example

The following example uses the functions described below. It implements the `log` function, which outputs information about the place where it was called.

#include <source_location>
#include <iostream>

void log(
  const char* 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() {
    log("Hello world!");
    fun("Hello C++20!");
}

## Output

```c++
file: main.cpp(24:8) `int main(int, char**)`: Hello world!

file: main.cpp(19:8) `void fun(T) [with T = const char*]`: Hello C++20!
```

What is the std::source_location in C++?

Built-in functions

Creation

Field access

Example

Output