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From: rdm@cernapo (Alphonse Rademakers)
Newsgroups: comp.sys.hp
Subject: Problem using shared memory on a HP 9000/720...
Message-ID: <RDM.91Apr24145822@aposalo.cern.ch>
Date: 24 Apr 91 12:58:22 GMT
Sender: news@cernvax.cern.ch
Distribution: comp
Organization: none
Lines: 185

Hi,
  I have a problem using shared memory (shm calls) on the HP 9000/720.
I've made a little program that creates a shared memory segment and
accesses it via an offset from a base array (in Fortran).
The offset from the base array was returned by the routine
that created the shared memory segment (in C). The creation of the shared
memory seems to be fine. Ipcs shows that it has been created with
the right protections. I can write nicely into the shared memory segment,
but as soon as I try to access it I get a 'memory fault'.

Could somebody (HP?) maybe solve this problem?

Attached is a small shar file containing the sample programs. Unpack and
run make_server and execute server. Commenting out the line
         K = IAAP(IOFFST+I)
in server.f makes the program run fine.
This example runs fine on DecStations and Silicon Graphics machines.

Thanks in advance,
   Fons Rademakers.



========= cut here ======

# This is a shell archive.  Remove anything before this line,
# then unpack it by saving it in a file and typing "sh file".
#
# Wrapped by Fons Rademakers <rdm@snake> on Wed Apr 17 20:09:11 1991
#
# This archive contains:
#	hcreateg.f	hcreates.c	make_server	server.f	
#

LANG=""; export LANG
PATH=/bin:/usr/bin:$PATH; export PATH

echo x - hcreateg.f
cat >hcreateg.f <<'@EOF'
*CMZ :          26/03/91  16.21.48  by  Fons Rademakers
*-- Author :    Fons Rademakers   20/03/91
      INTEGER FUNCTION HCREATEG(MFILE, IBASE, ISIZE, ICOMAD, IOFFST)
************************************************************************
*                                                                      *
* HCREATEG                                                             *
*                                                                      *
* Create a global section. This routine causes the pages at ICOMAD     *
* and continuing for at most ISIZE words (1 word = 4 bytes) to be      *
* mapped from file MFILE. MFILE will be created in the /tmp directory. *
* IOFFST is the offset between the address of the common starting at   *
* IBASE and the address of ICOMAD. The space in ICOMAD can then be     *
* addressed like: IBASE(IOFFST+1,...).                                 *
* On successful completion this function returns 0. In case of an      *
* error -ERRNO is returned.                                            *
* HCREATEG is an interface routine that calls the C routine HCREATEI.  *
*                                                                      *
* After a global section has been created by this function, other      *
* processes can use the data in this global section via the functions  *
* HMAPG and HFREEG.                                                    *
*                                                                      *
************************************************************************
*
      CHARACTER*(*) MFILE
      INTEGER       ICOMAD, ISIZE, IBASE, IOFFST, HCREATEI
*
      CHARACTER*4  MKEY
*
      MKEY = MFILE
      HCREATEG = HCREATEI(MKEY, IBASE, ISIZE, ICOMAD, IOFFST)
*
      END

@EOF

chmod 644 hcreateg.f

echo x - hcreates.c
cat >hcreates.c <<'@EOF'
/*CMZ :          03/04/91  17.29.25  by  Fons Rademakers*/
/*-- Author :    Fons Rademakers   20/03/91*/

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

int  shm_pawc;
long len;

int hcreatei_(mkey, base_common, size, comaddr, offset)
/*
 * mkey          identifier for the shared segment
 * base_common   address of base (PAW) common
 * size          length of common in 32 bit words
 * comaddr       starting address of the mapping (*)
 * offset        offset of comaddr in respect to the base_common (*)
 *               (*) = output variables
 */
long  base_common, *comaddr, *offset;
int   *size;
key_t *mkey;
{
   int             istat;
   int             flag = IPC_CREAT | 0666;
   unsigned long   off;
   char            *paddr, *shmat();

   len = *size * 4;

   /* create shared memory segment */
   if ((shm_pawc = shmget(*mkey, len, flag)) < 0) {
      perror("shmget");
      istat = -errno;
      return(istat);
   }

   /* attach shared memory segment */
   if ((paddr = shmat(shm_pawc, 0, SHM_RND)) == (char *)-1) {
      perror("shmat");
      istat = -errno;
   } else {
      istat    = 0;
      *comaddr = (long) paddr;
      off      = (*comaddr - base_common);
      *offset  = off >> 2;
   }
   return(istat);
}
@EOF

chmod 644 hcreates.c

echo x - make_server
cat >make_server <<'@EOF'
#! /bin/sh

cc -g -c hcreates.c
f77 -g +ppu -o server *.f *.o
@EOF

chmod 755 make_server

echo x - server.f
cat >server.f <<'@EOF'
      PROGRAM PRODUCE

      PARAMETER (LCOM = 10)
      CHARACTER*4 GNAME
      INTEGER     HCREATEG

      COMMON /AAP/ IAAP(LCOM)

      GNAME = 'pawg'
      IS = HCREATEG(GNAME, IAAP, LCOM, IGL, IOFFST)
      IF (IS .EQ. 0) THEN
         PRINT *, 'GLOBAL SECTION CREATED, begin address =',IGL,
     +            ' offset from AAP =', ioffst
      ELSE
         PRINT *, 'GLOBAL SECTION ERROR = ',IS
         STOP
      ENDIF

      J = 0

5     DO 10 I = 1, LCOM
         IAAP(IOFFST+I) = J
         K = IAAP(IOFFST+I)
10    CONTINUE
      PRINT *, IAAP(IOFFST+1)

      J = J + 1
      IF (J .LT. 5010000) GOTO 5

      END
@EOF

chmod 644 server.f

exit 0
--
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