How to get the absolute path for a given relative path programmatically in Linux?

Question

How to get the absolute path for a given relative path programmatically in Linux?

Incase of Windows we have the _fullpath() API. In other words, I mean

Answer 1

// For C++ with Gnome Gtkmm3 libraries
#include 
#include 

  string PathRel2Abs(string relpath) {
  Glib::RefPtr file = Gio::File::create_for_path(relpath);
  return file->get_path();
}