Re: [gforth] GForth callbacks

[Rene Hartmann]

I now boiled it down to a small example.

File call_binop.h:

#ifndef _CALL_BINOP_H_
#define _CALL_BINOP_H_

typedef int (*binop_callback)(int, int);

int call_binop(int a, int b, binop_callback callback);

#endif


File call_binop.c:

#include "call_binop.h"

int call_binop(int a, int b, binop_callback callback)
{
    return (*callback)(a, b);
}


I compile call_binop.c to a shared library libcall_binop.so and copy 
that to a standard lib directory (there seems to be no way to provide an 
-L option and setting LD_LIBRARY_PATH doesn't seem to work either!?)

Then I execute:

c-library binop-call
s" call_binop" add-lib
\c #include "call_binop.h"
c-function call_binop call_binop n n func -- n
c-callback binop n n -- n
end-c-library

: add + ;

' add binop CONSTANT cb_add
2 3 cb_add call_binop


giving:

*the terminal*:1: error: Invalid memory address
2 3 cb_add *call_binop*

If I add .s to the definition of add I see <-35568003> in the output.

So the callback has been executed, but something went wrong and I don't 
know how to avoid it.

--
René Hartmann


Am 03.09.2017 um 12:00 schrieb Rene Hartmann:
> I'm trying to use the C callbacks available with GForth 0.7.9 but 
> somehow it doesn't seem to work.
>
> I have a callback that takes two arguments and one return value.
>
> I define it like this:
>
>
> c-callback cs-renderer n a -- a
>
> ' render>buf cs-renderer CONSTANT c_render_to_buf
>
>
> When passing c_render_to_buf to the function which requires the callback 
> the callback gets invoked but when it returns things go wrong.
>
> If I place a .s in the callback it prints <-34288843> so it seems the 
> stack isn't set up properly. But I don't know what to do different to 
> make it work.
>
> I've yet to create a complete example I can post.
>
> --
> René Hartmann