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From: lutz@iks-jena.de (Lutz Donnerhacke)
Newsgroups: comp.lang.ada
Subject: Re: How to rename a file?
Date: Fri, 28 Sep 2001 07:39:08 +0000 (UTC)
Organization: IKS GmbH Jena
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Date: 2001-09-28T07:39:08+00:00
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* David Botton wrote:
>Ada arrays are passed as C arrays do to the import so the use of String is
>valid, we just need to Zero terminate. Ada record types are also passed as
>pointers, which makes life a lot easier.

There is no guarantee AFAIK. Even GCC (not to mention Ada) has different
ways to do this. Therefore I prefer passing Interfaces.C.Strings.char_p over
Interfaces.C.char_array over Standard.String. Especially, if you look how
Standard.String is implemented: As a small struct, passable in registers or
as a pointer to this struct. In the latter case your C-function may assume
the pointer to the memory area containing the string values and the bounds.

       -fpcc-struct-return
              Use the same convention for  returning  struct  and
              union  values  that is used by the usual C compiler
              on your system.  This convention is less  efficient
              for small structures, and on many machines it fails
              to be reentrant; but it has the advantage of allow�
              ing  intercallability between GCC-compiled code and
              PCC-compiled code.

       -freg-struct-return
              Use the convention that struct and union values are
              returned  in registers when possible.  This is more
              efficient     for     small     structures     than
              -fpcc-struct-return.

              If  you  specify  neither  -fpcc-struct-return  nor
              -freg-struct-return, GNU CC defaults  to  whichever
              convention is standard for the target.  If there is
              no  standard  convention,  GNU   CC   defaults   to
              -fpcc-struct-return.