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From: LEICHTER-JERRY@YALE.ARPA
Newsgroups: comp.os.vms
Subject: Re: Re-entrant code
Message-ID: <8704210356.AA10095@ucbvax.Berkeley.EDU>
Date: Mon, 20-Apr-87 22:56:45 EST
Article-I.D.: ucbvax.8704210356.AA10095
Posted: Mon Apr 20 22:56:45 1987
Date-Received: Wed, 22-Apr-87 00:33:13 EST
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: <LEICHTER-JERRY@YALE.ARPA>
Distribution: world
Organization: The ARPA Internet
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    As I once again learned, you have to disable interrupts (e.g. with a
    SYS$SETAST call) before calling non-re-entrant routines if AST routines
    also call them.  This is (obviously) to prevent the data structures in the
    non-re-entrant code from getting trashed.
    
    So what's the concern:  is it possible to write re-entrant code on a VAX
    in higher level languages like FORTRAN?  If so, are there guidelines writ-
    ten anyplace?  Thanks to all who reply.

In general, you have to avoid using any statically-allocated storage.  In
FORTRAN, this is mainly stuff in COMMON.  Note, however, that the FORTRAN
OTS is not all AST-reentrent - the I/O system, in particular.  (The same is
true of most language OTS's - C, for example.)

For TONS of details, read the Guide to Creating Modular Procedures on
VAX/VMS - a gem of a "good software engineering principles and practices"
book hidden away in the VMS documentation.  Section 3.3 is titled "Writing
AST-Reentrant Code".
							-- Jerry
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