Path: utzoo!attcan!uunet!cs.utexas.edu!know!samsung!uakari.primate.wisc.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!csi!mwette
From: mwette@csi.JPL.NASA.GOV (Matt Wette)
Newsgroups: comp.lang.fortran
Subject: Re: Calling a C function from Fortran.
Message-ID: <4482@jato.Jpl.Nasa.Gov>
Date: 3 Aug 90 14:01:44 GMT
References: <1990Aug2.191231.11783@portia.Stanford.EDU> <2425@l.cc.purdue.edu>
Sender: news@jato.Jpl.Nasa.Gov
Reply-To: mwette@csi.JPL.NASA.GOV (Matt Wette)
Lines: 35


In article <2425@l.cc.purdue.edu>, cik@l.cc.purdue.edu (Herman Rubin) writes:
|> In article <1990Aug2.191231.11783@portia.Stanford.EDU>,
volovich@dendrite.Stanford.EDU (Gene Volovich) writes:
|> > I'm calling a C function from a FORTRAN program on an RT running AOS, and 
|> > using the standard C compiler and f77.  I actually got this to run, but 
|> > my question is this: why does there need to be an underscore after
the name
|> > of the C function I'm calling?  Here's my code:
|> 
|> 			[Code deleted]
|> 
|> I do not know when this was introduced, but unlike the older systems I have
|> used, in many a name is not a name.
|> 
|> In all the Unix systems I have seen, if a Fortran program uses xyz
for a name
|> of a variable, function, subroutine, array, etc., it gets translated into 
|> _xyz_.  Similarly, the C name abc becomes _abc.  Thus if Fortran calls the
|> function pdq, the C function would have to be (in C) pdq_.   Also, Fortran
|> calls by reference, and C calls by value.  So if Fortran has the argument
|> x, it really passes the address of x, and C must use *x to get the value.
|> This is more understandable.


I see this as a very nice feature in Unix for the following reason:
It allows you to use Fortran and C libraries with mixed Fortran and
C sources.   Once I wrote mixed Fortran and C on a VAX and rand into
many  problems because many routines in the Fortran and C libraries
had matching names.  YECH!

 _____________________________________________________________________
 Matthew R. Wette		| Jet Propulsion Laboratory, 198-326
 mwette@csi.jpl.nasa.gov        | 4800 Oak Grove Dr, Pasadena,CA 91109
 ---------------------------------------------------------------------