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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.lang.f77
Subject: Re: Attempts at accessing signal(2) from within f77
Message-ID: <3193@sun.uucp>
Date: Sat, 25-Jan-86 04:48:39 EST
Article-I.D.: sun.3193
Posted: Sat Jan 25 04:48:39 1986
Date-Received: Sun, 26-Jan-86 06:01:40 EST
References: <611@eagle.ukc.UUCP>
Organization: Sun Microsystems, Inc.
Lines: 37

> In intro(3) it says "these functions together with those from section 2
> are automatically loaded by cc and f77". I took this to be reason enough
> that I could access signal(2) from a Fortran 77 program. Someone pointed
> out that "Ah yes! Loaded but not accessible" Huh? Can a clear explanation
> be given.

You can't call a section 2 or 3 C library routine from FORTRAN.  A FORTRAN
call to "foo" would be a call to a C routine called "foo_", and there's no
way to generate a call to a C routine called "foo".  As such, you can't get
at "signal(2)" from a FORTRAN program.

> A small test program (after several lager ones failed) was quickly written:
> 
> 	external junk,signal
> 	call signal(SIGFPE,junk)
...

First, put away the lager - never program when drunk. :-)  The problem with
this is twofold:

	1) SIGFPE is not declared, and in the grand (yecch) tradition of
	   FORTRAN, this means it creates a REAL variable (assuming no
	   "implicit" statement) - uninitialized, of course - and passes
	   its address as the first argument either to a FORTRAN routine
	   "signal" or a C routine "signal_".

	2) According to the 4.2BSD manual, the FORTRAN routine "signal"
	   (actually implemented as a C routine "signal_" takes three
	   arguments, not two.  4.1BSD may be the same; I don't know.
	   Look in your manual for a section on FORTRAN library routines;
	   "signal" will probably be in something called "signal(3F)".
	   This manual page will give more details on how to use "signal"
	   from FORTRAN.
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy%gorodish@sun.arpa	(yes, really)