Oppolzer - Informatik / Blog

Hello PL/1 list,

is this true? Are there any special restrictions concerning PL/1 mains and LE
enclaves calling each other?

Please read my original post, too. Do you have any further suggestions?

Thank you, kind regards

Bernd



B.D. wrote:

Ran across that at a client. I believe that the PL/I manuals document that an LE
enabled program cannot call a PL/I MAIN.

On Tue, 27 Mar 2012 18:16:06 +0200 Bernd Oppolzer wrote:

 > Hello all,
 >
 > we have a problem that is not easy to describe. Let me try it.
 >
 > We are building a test supporting system, which allows to do tests of
 > software components. The system consists of the following modules or
 > parts:
 >
 > A - driver, written in ASSEMBLER. The driver builds a LE enclave, so
 > that it can call C subfunctions and the test objects, which are
 > (normally) PL/1 routines
 >
 > B - driver supporting routine, written in C. This routine provides
 > services OPEN, WRITE and CLOSE. It is called by the driver. On OPEN, it
 > fetches a testcase list from the testcase database and builds a linked
 > list in memory (in the LE heap). It also opens a log file for writing.
 > On WRITE, it writes some protocol data on the log file. On CLOSE, it
 > closes the log file.
 >
 > C - driver exit, written in ASSEMBLER. It is called at the beginning of
 > the test object (at the entry point) by means of TRAP2 interrupts. It
 > has access to the testcase list element that B took from the testcase
 > database for the current testcase. It then calls D, passing the address
 > of the testcase list element. D reads the testcase data, builds a
 > parameter list for the testcase, and returns a parameter list. Then the
 > driver exits resumes the test object at the position of the entry point
 > (this way the test data is passed to the test object).
 >
 > D - is a C routine which reads the data from the testcase data base and
 > builds the parameter list for the test object - because this is much
 > easier to do in C than in ASSEMBLER.
 >
 > Now the problem:
 >
 > all works well, if the test object is a PL/1 subroutine and not a main
 > program. Then the LE enclave built by A is used by B, passed to the test
 > object, and used by D as well. There is no problem passing the LE
 > environment through the TRAP2 interrupt.
 >
 > But:
 >
 > we also want to be able to test PL/1 main programs this way. The PL/1
 > main programs are called by the driver the same way as the modules are
 > called, but because they are started at CEESTART, a second LE enclave
 > below the first enclave is built. Then C and D run below the second
 > enclave. This is no problem so far, because there is no need to share
 > ressources between the two enclaves; the only information exchange is
 > through the testcase list element which belongs to the heap of the first
 > enclave, and this is no problem, in our opinion.
 >
 > But:
 >
 > when we return from the test object and we try to execute the WRITE call
 > to B in the first enclave, it fails in the prologue of B.
 >
 > We first thought that reg 12 had not be restored correctly, but this is
 > not the case. Reg 12 is the same as before the call of the PL/1 main,
 > points to the original CEECAA. Also, the save area (including NAB etc,
 > the words behind offsets 72) are unchanged. But still, we get abends 0C4
 > etc. in the prologue of B. But only in the PL/1 main case, if there is a
 > second enclave, not in the other case.
 >
 > We fixed this problem by doing the WRITE and CLOSE calls not in the same
 > (first) enclave as the OPEN call, but instead we did all the subsequent
 > calls by an intermediate PL/1 main, that is: after the PL/1 test object
 > main destroyed somehow our first enclave, we didn't use it any more, but
 > instead constructed new enclaves for every subsequent call at the same
 > level. But this doesn't look very sound to me.
 >
 > My question is: has somebody out there an idea, what has happened here
 > and what might be a solution to our problem? Is it possible to have one
 > LE enclave call another and on return from the second still have the
 > first one usable? What are we getting wrong?
 >
 > Kind regards
 >
 > Bernd
 >
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--
Binyamin Dissen <bdissen@dissensoftware.com>
http://www.dissensoftware.com

Director, Dissen Software, Bar & Grill - Israel