IMO, writing an exit in LE C/C++ just isn't worth the hassle. To write a
proper glue code stub you will need to call your C program via the LE
CEEPIPI service. Trying to get the CAA from the TCB is a shot in the
dark as each ISPF screen runs in a subtask, and IIRC using the SELECT
CMD(...) service will use ATTACH. I'm not sure what TCB in the hierarchy
LE stores the CAA.
Check out the Metal/C or Systems Programming C (SPC) features of the
compiler, both of which will suffice for writing an exit.
Tom Quarendon wrote:
Anyone have any wisdom or experience of writing a VDEFINE user exit for ISPF in
C?
My experience so far is mixed, it certainly isn't as easy as writing a C
function and making it
#pragma linkage(OS)
and passing its entry point to ISPF.
At least one problem seems to be that when running "interactively" from TSO
your exit gets called on a different subtask. Don't know whether the terminology there is
right, but either way the Language Environment isn't initialised - getting the LE anchor
pointer from the TCB fails. Running from batch seems better, the LE anchor seems to be
present - so exit seems to be run on same task(?).
You seem to have to write the exit in assembler and use the CEEENTRY macro to
define the prolog/epilog of the function in order to get LE initialised and to
be able to call to other C functions.
Anyway I've got a fair way, but it all seems rather a battle, so I was hoping
there was something simple I'd missed. I'm also worried that if I'm creating a
new LE enclave each time (as the CEEENTRY macro will do in the TSO case) it's
going to be hopelessly inefficient, even if it does work. Having a separate LE
enclave is really not helpful anyhow as I want access to the global variables
that I might have set before I called into ISPF.
Any wisdom would be gratefully received.
Tom Quarendon.
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