std::experimental::source_location::line(3)

NAME
std::experimental::source_location::line - std::experimental::source_location::line

Synopsis
   constexpr std::uint_least32_t line() const noexcept; (library fundamentals TS v2)
   Returns the line number represented by this object.

Parameters
   (none)

Return value
   The line number represented by this object.

Example
// Run this code
 #include <experimental/source_location>
 #include <iostream>
 #include <string_view>
 using std::experimental::source_location;
 inline void cur_line(
     const std::string_view message = "",
     const source_location& location = source_location::current())
 {
     std::cout
         << location.line() // <- the call-site line #
         << ") "
         << message;
 }
 int main()
 {
     cur_line("++" "\n");
     cur_line(); std::cout << "Hello," "\n";
     cur_line(); std::cout << "C++20!" "\n";
     cur_line("--" "\n");
 }

Output:
 18) ++
 19) Hello,
 20) C++20!
 21) --

See also
   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)
   C++ documentation for
   Filename and line information