std::experimental::source_location::current (3) - Linux Manuals
static constexpr source_location current() noexcept; (library fundamentals TS v2)
Constructs a new source_location object.
If current() is invoked directly (via a function call that names current()), it returns a source_location object with implementation-defined values representing the location of the call. The values should be affected by the #line_preprocessor_directive in the same manner as the predefined macros __LINE__ and __FILE__.
If current() is invoked in any other manner, the return value is unspecified.
If current() is used in an initializer_for_a_non-static_data_member, the return value corresponds to the location of the constructor or aggregate_initialization that initializes the data member.
When current() is used in a default argument, the return value will correspond to the location of the call to current() at the call site.
constructor (public member function)