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From: dbotton@hotmail.com
Subject: Re: Tasks and C/C++ code.
Date: 1998/11/11
Message-ID: <72b35b$pll$1@nnrp1.dejanews.com>#1/1
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References: <364702E5.F6987321@hiwaay.net> <729ndu$jfo$1@nnrp1.dejanews.com>
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Date: 1998-11-11T00:00:00+00:00
List-Id: <comp.lang.ada>

I think it would be practical to create a protected type that wrapped your C
function to insure that it is not be run concurrently (if it isn't safe). If
it's safe then just call it as you would any other Ada Procedure/Function.

David Botton


  dennison@telepath.com wrote:
> In article <364702E5.F6987321@hiwaay.net>,
>   bdorough@phaseiv.com wrote:
> >     I am working on a project where we need to call the same C function
> > from multiple tasks.  I am wondering how to do this safely.  Can I make
> > a generic with my C pragma defined there are do I need to define the
> > prama in the task type so each task will have its own copy of the C
> > function.
>
> If the C function truly isn't safe to call from multiple threads (iaw: relies
> on global data, "static" local declarations, or calls other non-thread safe
> routines) then you have to ensure that calls to it happen from only one
> thread. The safest way to do it is to make *one* server task responsible for
> calling the routine and returning its results. Client tasks rendezvous with
> the server task to request a call to the unsafe C routine. This is the method
> used in at least one set of X/Motif Ada bindings.
>
>
> --
> T.E.D.
>

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