Passing an Ada array to a C function

Passing an Ada array to a C function

[Lin]

If an Ada array holds the pointers pointing to a String (char_array), 
how can I pass the Ada array to an C funtion with an array as formal
parameter? Is the "char_array" of Ada occupies the same bytes as the
"char" of C?

Many thnks.

Re: Passing an Ada array to a C function

[David Botton]

procedure My_C_Func (S : Interfaces.C.char_array);
pragma Import (C, My_C_Func);

is equal to

void My_C_Func (char* s);

A Char_Array contains more information than a char* and does not per se
occupy the same number of bytes, but take a look at the ref manual where it
describes that compilers must make the above possible.

The Ada interface to C in most code and bindings I have seen highly
underused. There is all kinds of neat stuff you can do by just setting up
the procedure specs properly. Take a look at the body of some of the
GWindows packages (http://www.adapower.com/gwindows) for some good ideas. I
chose not to write a set stand alone thin Win32 bindings since that would
cripple the power of the Ada interface to C and instead tailored each import
spec in the function body to match what I wanted to accomplish.

David Botton



----- Original Message -----
From: "Lin" <lin@post.com>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: Monday, September 10, 2001 9:21 PM
Subject: Passing an Ada array to a C function


> If an Ada array holds the pointers pointing to a String (char_array),
> how can I pass the Ada array to an C funtion with an array as formal
> parameter? Is the "char_array" of Ada occupies the same bytes as the
> "char" of C?
>
> Many thnks.
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada.eu.org
> http://ada.eu.org/mailman/listinfo/comp.lang.ada
>

Re: Passing an Ada array to a C function

[Thierry Bernier]

David Botton a écrit :

> procedure My_C_Func (S : Interfaces.C.char_array);
> pragma Import (C, My_C_Func);
>
> is equal to
>
> void My_C_Func (char* s);

void My_C_Func (const char *s);


--
Thierry Bernier

Re: Passing an Ada array to a C function

[David Botton]

Depends on the age of your compiler. C and C++ were designed by committee
(to "have fun") unlike Ada so things are very rarely concrete.

> void My_C_Func (char* s);

> void My_C_Func (const char *s);


David Botton

Re: Passing an Ada array to a C function

[Robert Dewar]

"David Botton" <David@Botton.com> wrote in message news:<mailman.1000953137.8671.comp.lang.ada@ada.eu.org>...
> Depends on the age of your compiler. C and C++ were designed by committee
> (to "have fun") unlike Ada so things are very rarely concrete.
> 
> > void My_C_Func (char* s);
>  
> > void My_C_Func (const char *s);
> 
> 
> David Botton


I don't think it is fair to claim that C and C++ were
designed by committee any more than Ada was.

In all three cases, the basic language design was the work
of a single coherent design team (in the Ada case, this was
more of a team, in the C++ case, more of an individual).

The preliminary design was then debated and (significantly)
modified by a committee (Ada 95 would not have looked the
same if the design team had been able to follow only its
own preference :-)

Let's not make the mistake of bashing C and C++ where 
the bashing is not fair :-)