Re: Interface to C; Storage_Error

[Chris <enderx12@my-deja.com>]

In article <3a409667.1742507013@paragate1>,
  twolf@acm.org wrote:
> Name most certainly cannot be alloc'd by that C routine (it's a
> "char *" passed by value). Your Ada interface however passes a
> "char **"...
>
> I'd start there for looking for errors. What does the spec
> (if it exists) for the C routine say about that argument? Is
> it really a "char *"? If so, change the Ada declaration to
> "Name : in chars_ptr". What does it have to point to upon entry?
> What does the routine do with the memory pointed to? (How large
> must the memory area pointed to by Name be?)
>
> If the C routine really allocs Name, the C parameter type most
> probably is "char **"...

Argh. When all else fails, RTF.H carefully. Or at least the example
code. The spec doesn't actually spell it out, but Name is supposed to
be pointing to a 255-byte array of char.

What I'd like to do is have a semi-thick binding where users of the
package get ( ... Name : out String; Val : out double; ... ). So the
trick is to get the C function to fill a buffer I allocate in Ada, then
get that into an Ada String to send back to the caller.

So my initial thought is to declare the name parameter in the C
function as "in out char_array", then the wrapper function would return
its "Name := To_Ada(Name_Char_Array);". How does this sound?

Ugh, I hate C. If I wanted to program in assembler, I'd do so.

--chris



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