From:	SMTP%"westfall@TeleCheck.com" 28-OCT-1994 16:23:40.47
To:	EVERHART
CC:	
Subj:	lib$find_image_symbol on OpenVMS AXP V1.5

From: westfall@TeleCheck.com (Roy Westfall)
X-Newsgroups: comp.os.vms
Subject: lib$find_image_symbol on OpenVMS AXP V1.5
Date: 28 Oct 1994 19:21:59 GMT
Organization: The Black Box, Houston, Tx (713) 480-2686 
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A couple of weeks ago I posted a message about a problem
I was having with LIB$FIND_IMAGE_SYMBOL on an alpha.  I
have discovered the source of the problem and it goes
something like this.

IF you have a shareable image linked against the DEC CXX 
rtl and you use lib$find_image_symbol to load that
image from an image that is NOT linked against DEC CXX,
the load causes some memory to become corrupted and either
an immediate exception occurs, or an exception occurs during
some later processing (usually in C rtl functions).  Easily
duplicated with the following code:

$ TYPE BREAK.COM
$   CXX /OBJECT=SHARED.OBJ SYS$INPUT
#include <iostream.hxx>
extern "C" X() { return 1; }
$   LINK/SHAREABLE=SHARED.EXE SHARED.OBJ,SYS$INPUT/OPT
symbol_vector=(X=procedure)
$   CC /OBJECT=FIND.OBJ SYS$INPUT:
#include <stdio.h>
#include <lib$routines.h>
#include <descrip.h>
 $DESCRIPTOR(file,"TEST");
 $DESCRIPTOR(symbol,"X");
int main(int argc, char *argv[])
{
    int status;
    void *value;

    printf("seeking %s in %s\n",symbol.dsc$a_pointer,file.dsc$a_pointer);
    status = lib$find_image_symbol (&file, &symbol, &value, 0);
    lib$signal(status);
    printf("status=%d, value=%u\n",status,value);
}
$   LINK /EXECUTABLE=FIND.EXE FIND.OBJ
$   DEFINE TEST SYS$DISK:[]SHARED.EXE
$   RUN FIND
$ SET VERIFY
$ @BREAK.COM
$   CXX /OBJECT=SHARED.OBJ SYS$INPUT

#include <iostream.hxx>
extern "C" X() { return 1; }

$   LINK/SHAREABLE=SHARED.EXE SHARED.OBJ,SYS$INPUT/OPT
symbol_vector=(X=procedure)
$   CC /OBJECT=FIND.OBJ SYS$INPUT:

#include <stdio.h>
#include <lib$routines.h>
#include <descrip.h>
 $DESCRIPTOR(file,"TEST");
 $DESCRIPTOR(symbol,"X");
int main(int argc, char *argv[])
{
    int status;
    void *value;

    printf("seeking %s in %s\n",symbol.dsc$a_pointer,file.dsc$a_pointer);
    status = lib$find_image_symbol (&file, &symbol, &value, 0);
    lib$signal(status);
    printf("status=%d, value=%u\n",status,value);
}

$   LINK /EXECUTABLE=FIND.EXE FIND.OBJ
$   DEFINE TEST SYS$DISK:[]SHARED.EXE
$   RUN FIND   
seeking X in TEST
%SYSTEM-S-NORMAL, normal successful completion
%SYSTEM-F-ACCVIO, access violation, reason mask=00, virtual address=00000034, PC=0048A064, PS=0000001B
%TRACE-F-TRACEBACK, symbolic stack dump follows
 Image Name   Module Name     Routine Name    Line Number  rel PC      abs PC
 CMA$RTL                                                0 00030064    0048A064
                                                        0 8036B2C8    8036B2C8
                                                        0 8036F158    8036F158
 FIND         .MAIN.          main                   2536 00000124    00030124
 FIND         .MAIN.          __main                    0 00000058    00030058
                                                        0 BD5C48F0    BD5C48F0
%SYSTEM-F-ACCVIO, access violation, reason mask=00, virtual address=00000034, PC=0048A064, PS=0000001B

  Improperly handled condition, image exit forced.
    Signal arguments:   Number = 00000005
                        Name   = 0000000C
                                 00000000
                                 00000034
                                 0048A064
                                 0000001B

    Register dump:
    R0  = 0000000000000001  R1  = 0000000000000000  R2  = 000000000045DBA0
    R3  = 0000000000000000  R4  = 00000000001462C1  R5  = 00000000002C2EA0
    R6  = 0000000000290150  R7  = 00000000002C2ECC  R8  = 0000000000000001
    R9  = 000000007FFA0410  R10 = 000000007FFA1190  R11 = 000000007FFBE3E0
    R12 = 000000000000005D  R13 = FFFFFFFFBD5C76A8  R14 = 0000000000000000
    R15 = 0000000000000000  R16 = 0000000000000034  R17 = 00000000001445A8
    R18 = 000000000000001D  R19 = 0000000000030000  R20 = 0000000000522758
    R21 = 0000000000000018  R22 = 0000000000522780  R23 = 00000000005226E0
    R24 = 000000000051EA68  R25 = 0000000000000001  R26 = 000000000049A188
    R27 = 000000000046C300  R28 = FFFFFFFFFFFFFF50  R29 = 000000007FD2AC60
    PC  = 000000000048A064  PS  = 200000000000001B
$


                                                                      
The fix is to make sure the image doing the lib$find_image_symbol is linked
against the DEC CXX rtl.

--
-------------------------
Roy Westfall
westfall@telecheck.com

The views expressed here
are not necessarily shared
by my employer.