Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!elroy.jpl.nasa.gov!mahendo!wlbr!mh
From: mh@iti.org (Mike Hoegeman)
Newsgroups: comp.protocols.nfs
Subject: Re: bug in sun-3/os4.1 rpc/xdr?
Message-ID: <56999@wlbr.IMSD.CONTEL.COM>
Date: 15 Aug 90 22:38:44 GMT
References: <90225.174053BACON@MTUS5.BITNET>
Sender: news@wlbr.IMSD.CONTEL.COM
Reply-To: mh@tweedledum.imsd.contel.com.UUCP (Mike Hoegeman)
Organization: Contel FSD, Westlake Village, CA
Lines: 78

In article <90225.174053BACON@MTUS5.BITNET> BACON@MTUS5.BITNET (Jeffery Bacon) writes:
 >I submit the following problem:
 >Given the following declaration (taken just about right out of the Sun 4.1
 >netowrk prog guide) bla.x:
 >-------------
 >program BLAPROG { version BLAVERS {int BLA(int) = 1; } = 1; } = 0x20000099;
 >--------------
 >This should send an integer and receive an integer.
 >For this, I've written the following server procedure:
 >--------------
 >int *bla_1(oog) int *oog; { int erg = 5; printf("%d\n",*oog);return(&erg); }
 >--------------
 >(please forgive my lack of formatting, but this is pretty simple; I wrote it
 >on the fly)
 >And for the client side, a simple little program:
 >-----------------
 >#include <stdio.h>
 >#include <rpc/rpc.h>
 >#include "bla.h"
 >main() {
 >	CLIENT *bla;
 >	int *result, oog;
 >	bla=clnt_create("ctsee8",BLAPROG,BLAVERS,"tcp");
 >	oog=44;
 >	result=bla_1(&oog,bla);
 >	printf("%d\n",*result);
 >}

(poster goes on to explain that sometimes the server program returns garbage.)

 answer: the problem is in your server procedure

 >int *bla_1(oog) int *oog; { int erg = 5; printf("%d\n",*oog);return(&erg); }

 the statement 
     int erg = 5;

 should be 
     static int erg; 
     erg = 5;

You are returning pointer to a int which is a variable that goes out of
scope by the time the service transport to returns that value. That is why 
you sometimes get back garbage. You are just getting 'lucky' in the cases
where it seems to work.

If you find making 'erg' static repugnant , you can do something like this
inside of bla_1

    int *
    bla_1(oog)
	int *oog;
    {
	extern SVCXPRT *MyXprt;
	int erg;
	:
	<processing to produce value for erg here>
	:
	svc_sendreply(MyXprt, xdr_int, &erg); /* xprt is the SVCXPRT * 
						created at via
						something like
						svcudp_create or
						svctcp_create */

	return ((int *)0); /* the return of a NULL pointer 
			  tells the server machinery that you
			  have already sent the reply back yourself. */
    }

the above is off the top of my head , you can check the man page on
svc_sendreply() to make sure it's right


-mike h.
--
-------------------------------------------------------------------------------
Mike Hoegeman               email: mike@wlv.imsd.contel.com  tel: (818)706-4145
Contel Federal Systems      31717 La Tienda Dr, Westlake Village CA. 91359