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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: Interfaces.C.String.Update
Date: Mon, 28 Nov 2011 08:22:08 -0800 (PST)
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Date: 2011-11-28T08:22:08-08:00
List-Id: <comp.lang.ada>

awdorrin wrote on comp.lang.ada:
> What is the suggested method to null terminate an Ada string being
> passed back to C via Interfaces.C.Strings.Update() ?
>
> I've been looking at the code for i-cstrin.adb, and it seems that by
> default that the procedure, when passing in an Ada String, uses To_C
> with Append_Null =A0set to False.
>
> I was trying to determine if I should manually place the null
> character, or instead call Update like:
>
> Update( cPtr, 0, To_C( AStr, Append_Nul =3D> True), False);
>
> I haven't been able to find any discussions on this, so I'm just not
> sure what the 'best' approach for this would be.

I think you are correct, perhaps a more terse idiom would be:

Update( cPtr, 0, AStr & ASCII.NUL, False);

This is because, if Check is True,

procedure Update (Item   : in chars_ptr;
                  Offset : in size_t;
                  Chars  : in char_array;
                  Check  : Boolean :=3D True);

assumes that Item is null-terminated on input in order to call
Strlen (Item), but does not require Chars to be null-terminated
because
Chars is a char_array with known bounds.  If Item is not null-
terminated
before you call Update, you're in for C-style trouble :)

If Check is False, all bets are off, so you'd better null-terminate
Item manually.

--
Ludovic Brenta.
The synchronized executive talents result in the functional successful
execution.