[R] What exactly does rchkusr() do?

[Guilherme Veiga da Rocha]

	Hi all,
	
	I am trying to compile a fortran routine originally written for R  
from within matlab.
	
	It all worked fine, but the newest version of the Fortran code has a  
call to rchkusr() and I now get a message that this is an undefined  
symbol.
	
	I am under the impression that rchkusr() just serves to let the  
processor take care of interruption messages (typically, the user  
frantically pressing Ctrl-C to stop running).
	a) Is that right?
	
	Another two questions are:
	1 - If I choose to keep this "interruption checkpoint" in the  
routine, what library is  rchkusr() in and how do I link it when  
compiling the Fortran object?
	2 - True of False: If I choose to comment that line, that just means  
that the user will not be able to stop running the calculations while  
the processor executes the Fortran bit of the code.
	
	Answers to any of the a, 1, 2 questions above is welcome.
	
	And in case you are wondering:
	- I am trying to link the Fortran to matlab so I can compare results  
to other similar routines coded in matlab;
	- This is in the glasso package by Friedman, Hastie, Tibshirani.
	
	Thanks for any help.
	
	Cheers,
	
	Guilherme Rocha