topic Re: Exception Handling in Operating System - OpenVMS

Exception Handling

Steve Lobsinger — Wed, 09 Feb 2005 16:20:48 GMT

Hi -

I'm working with an openVMS Alpha system (6.2, I think) and have a situation where a C program calls a Fortran subroutine. Inside the fortran procedure, the LIB$ESTABLISH call is made to handle exceptions.

My question is this: Assume an exception occurs in the Fortran subroutine. Control will then pass to the specified exception handler to do it's work. Once the exception handler has completed, where does control return to? Does it go back to the next line in the fortran subroutine? Does it return to the calling C routine?

Thanks in advance!!

-steve

Re: Exception Handling

Travis Craig — Wed, 09 Feb 2005 18:51:02 GMT

Steve,

I think you can do it either way. This link discusses it some:

http://h71000.www7.hp.com/doc/731FINAL/5841/5841pro_032.html

I think if your condition handler returns SS$_CONTINUE then it will return to the Fortran routine, either the line that caused the problem or the next one, depending on what it is.

Returning to the C program looks complicated in that description, but I think you can also use LIB$SIG_TO_RET to make it simple.

It's been many years since I've done this, but I hope these pointers help.

--Travis

Re: Exception Handling

Kris Clippeleyr — Thu, 10 Feb 2005 02:13:01 GMT

Steve,

Where the condition handler returns to after dealing with the error, is entirely up to the way the condition handler is written. It can return to the statement following the one that caused the excption, it can return to the "caller of the establisher", or even unwind more call frames and return to somewhere else in the program. I think you have to have a thorough look at the handler.

Regards,
Kris (aka Qkcl)

Re: Exception Handling

Steve Lobsinger — Thu, 10 Feb 2005 09:34:54 GMT

Travis -

Thanks for the info and the link. I think from the information you gave I can get where I need to go.

Thanks!
-steve

Re: Exception Handling

Steve Lobsinger — Thu, 10 Feb 2005 09:37:21 GMT

Kris -

You are right about needing to know what the condition handler is doing...and that's what I've got to write!

I should be able to figure out how to get it to return control to where I want upon return...I hope. If not I'm sure you guys will hear from me again!

Thanks for the great replies!

-steve