What exactly is std::labs() there for?
C++11 was when std::labs and std::llabs were added. This was part of the partial syncing done to the C++ standard library with the C99 standard library.
You don't really need it in C++ code, because we had a long overload of std::abs since about forever. But if you have some C code (that by sheer coincidence also compiles with a C++ compiler), and it uses labs, you can build it with a C++11 compiler and standard library.
In retrospect, there is one marginally useful use case for these functions. And that is when an attempt to use std::abs is ambiguous. For instance:
template<typename T>T run_func(T (&f)(T)) { return f({});}Then trying to call run_func(std::abs); is ill-formed. We need to either specify the template argument explicitly or cast std::abs to the proper type. On the other hand run_func(std::labs); isn't ambiguous, and not too verbose.
Still, not too useful.