From: Glenn Wolf [r39604@pulsar.sps.mot.com]
Sent: Friday, June 11, 1999 11:51 AM
To: Info-VAX@Mvb.Saic.Com
Subject: Re: Signal handling and tracebacks

system@SendSpamHere.ORG (Brian Schenkenberger, VAXman-) writes:

> 
> If you could share the code in the condition handler, that might help
> 
How's your fortran?  Here's a snippet, without all the fortran declaration
rigamarole.  There's a little more (very little) to the actual production 
routine, but the problem I see is when this path is executed.

	integer*4 function Cue_Error_SignalHandler (sigArgs, mechArgs)

	if ((sigargs(2) .and. STS$M_FAC_SP) .or. .not. (sigargs(2) .and. STS$K_SEVERE)) then
!	    Signal is either non-fatal, or facility specific.  Generate a traceback 
!	    so we can find out where the error occurred.  Do this by signalling with 
!	    the severity set to warning.  The traceback handler will catch this, 
!	    generate the trace, and return.

	    Call Lib$Signal(%val(sigargs(2) .and. (.not. 7)))

!	    Now, get the message for the real error & severity, and put it
!	    in the CUE message buffers where the caller can find it

	    Call Lib$Sys_GetMsg(sigargs(2), 	! Get message indicator
     &			        KeyLength, 
     &			        ErrorKey, 
     &			        FacilityMask+SeverityMask+MessageMask)
	    Call Lib$Sys_GetMsg(sigargs(2), 	! Get message text
     &			        TextLength, 
     &			        ErrorText,
     &			        TextMask)
	    Call Cue_Error_Set(ErrorKey(:KeyLength), ErrorText(:TextLength))

!	    Simulate LIB$SIG_TO_RET, except that the stack is unwound to the
!	    establisher of the condition handler, not its caller

	    if (mechargs(1).eq.4) then
	        ! We're on a VAX
	        depth = mechargs(3)
	        mechargs (4) = sigargs(2)
	    else
	        ! We're on an Alpha
	        depth = mechargs(5)
	        mechargs (13) = sigargs(2)	! status to be returned
	        mechargs (14) = 0
	        ! On ALPHA the next item is the top half of R0.
	        ! On VAX the next item is R1, which is harmless.
	    endif

	    ! check status of:  unwinding stack, to establisher, no alt. PC
	    call Gut_Check (Sys$Unwind (depth, %val(0)))
	    Cue_Error_SignalHandler = 1			! We handled the condition
	else
	    ! we don't know how to handle any other signal.
	    ! resignal everything else.
	    Cue_Error_SignalHandler = 0
	endif
	> 
> 
> You can pick up a sample of both SNAPSHOT and TRACER (the callable
> symbolic traceback) from ftp://ftp.tmesis.com.  There are several
> examples demonstrating how to call the traceback there as well:
> TRACER_CALLING_DEMO.{FOR,C,MAR}
> 
> UNZIP the SNAPSHOT and/or TRACER files and then, VMSINSTAL them.
> 
> --
I've pulled them down, and will look into them.  Thanks for your help.
-- 
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Glenn D. Wolf                                    Motorola SPS
business: Glenn_Wolf@email.sps.mot.com           SPS IT CIM Solutions    
personal: Glenn_D_Wolf@msn.com                   426 North 44th St. 
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