From: "Adam Beneschan" <adam@irvine.com>
Subject: Re: Interfacing with C - pointer problem
Date: 31 Jan 2007 10:10:51 -0800
Date: 2007-01-31T10:10:51-08:00 [thread overview]
Message-ID: <1170267048.731810.18900@k78g2000cwa.googlegroups.com> (raw)
In-Reply-To: <aP-dnTYI5YPAKSLYnZ2dnUVZ_oWdnZ2d@comcast.com>
On Jan 30, 1:10 pm, tmo...@acm.org wrote:
> > type LPSTR is access all String;
>
> > This does not work correct. What I found is, that data'Address is 32
> > bit and LPSTR is 64 bit.
>
> Because LPSTR points to a dynamic size string and thus needs to
> carry along bounds information. A C LPSTR does not point to a dynamic
> string, but instead points to a single character - the first in the
> string. So the match is
> type LPSTR is access Interfaces.C.Char;
> procedure C_Func (x : LPSTR); -- expects an address (C-pointer, 32-bit)
> and then
> data : Interfaces.C.char_array := Interfaces.C.To_C("ABC");
> and
> C_Func (data(data'first)'unchecked_access);
Or perhaps better:
procedure C_Func (x : Interfaces.C.Strings.chars_ptr);
data : aliased Interfaces.C.char_array := Interfaces.C.To_C
("ABC");
C_Func (Interfaces.C.Strings.To_Chars_Ptr (data'unchecked_access));
May as well use the stuff Ada provides for this exact purpose.
-- Adam
next prev parent reply other threads:[~2007-01-31 18:10 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-30 14:23 Interfacing with C - pointer problem Gerd
2007-01-30 15:53 ` Frank J. Lhota
2007-01-30 21:10 ` tmoran
2007-01-31 18:10 ` Adam Beneschan [this message]
2007-01-31 23:53 ` Jeffrey R. Carter
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