Launch executable with xdg-open

I am trying to write a function launchSystemFile which works like windows ShellExecuteEx from the command line or from C++. If I ShellExecuteEx a blah.txt it opens it in the default editor. If I ShellExecuteEx a firefox.exe it launches the executable. I have been doing from C++ popen "xdg-open blah" and it works great except for executables. Is there anyway to make xdg-open execute an executable? Such as Firefox at path /usr/lib/firefox/firefox? I tried xdg-open "/usr/lib/firefox/firefox" but this fails with the error message: > gvfs-open: /usr/lib/firefox/firefox: error opening location: No application is registered as handling this file