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From: jkr@gitpyr.UUCP (John Kenneth Riviere)
Newsgroups: net.micro.pc,net.lang.pascal
Subject: Re: local variable in assembly routine to be call from TURBO PASCAL
Message-ID: <1090@gitpyr.UUCP>
Date: Mon, 25-Nov-85 22:46:49 EST
Article-I.D.: gitpyr.1090
Posted: Mon Nov 25 22:46:49 1985
Date-Received: Tue, 26-Nov-85 21:00:13 EST
References: <1165@princeton.UUCP> <1062@gitpyr.UUCP>
Reply-To: jkr@gitpyr.UUCP (John Kenneth Riviere)
Distribution: net
Organization: Georgia Institute of Technology
Lines: 33
Xref: watmath net.micro.pc:6011 net.lang.pascal:396
Summary: Use typed constants.

In article <1165@princeton.UUCP> wei@princeton.UUCP (P Wei) writes:
>
>My final goal is to set a 'static local variable' (like in C) such that on
>second entry into this routine I can still get the value of variable set last
>time.  From the TURBO reference manual, the local variable is stored in stack
>segment. So I think the above routine is not going to work. Can anyone tell
>me a workable procedure ?
>Thanks.
>HP Wei   (wei@princeton)

I have not responded earlier in hopes that someone else will point this
out for me, but as I have not seen this solution suggested yet I guess I
will add my $.02.

It is not obvious from the Turbo Pascal manual unless you read it carefully,
but it is possible to declare what amounts to a static local variable within
a procedure or function by declaring it as a typed constant.  These are
the initialized constants that Turbo allows and the space for them is allocated
in the code segment which will not change from one recursion to another (except
as the procedure's code changes it).  They are not really constants since it
is possible to change their values, but they seem to be frequently overlooked
since their declaration indicates that they are constants.  I haven't tried
using them with inline code, but in Chapter 20 of my Turbo 3.0 manual it
specifically mentions typed constants as being accessible through the CS
register when doing inline code.  Note that if the procedure in question is
being reloaded from an overlay file then the initial value will be reloaded
along with the rest of the code so it is not static in this case, but other-
wise it should be OK.  Hope this helps.

-- 
J. Kenneth Riviere   (JoKeR)
Georgia Institute of Technology, Atlanta Georgia, 30332
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