Re: calling c from gprolog

[Daniel Diaz]

Output arguments are handled with a pointer to the type. E.g. a output 
integer (-integer) is handed as: int *pout. Similarly a string (char *) 
is handled as a char **pout. Here is a correct version of your example:


#include "gprolog.h"

Bool test(char *in, char **pout){

  *pout = (char *) malloc(1024*sizeof(char));

  sprintf(*pout, "teste");
  printf("IN:%s\n", in);

  return TRUE;          /* succeed */
};




Pedro Salgueiro wrote:
> Hi.
> I'm trying to call c from gprolog and I have some
> problems when I use the foreign type "-string" to
> obtain the result of the c function.
>
> This the file teste.c:
>
> #include "gprolog.h"
>
> Bool test(char *in, char *out){
>
>   //out = (char *) malloc(1024*sizeof(char));
>   //out = (char *) alloca(1024);
>
>   sprintf(out, "teste");
>   printf("IN:%s\n", in);
>  
>   return TRUE;		/* succeed */
> };
>
>
> And this is the file test.pl
>
> :- foreign(test(+string,-string)).
>
> when I compile both of them with:
> gplc test.c test.pl
> I get an executable file.
> When I run this file and enter "test(xpto, X)."
> gprolog 
> just crahs, with the folowing error:
>
> Fatal Error: Segmentation Violation
>
> Anyone knows how to put this little exmaple working.
>
> Thank's.
> Pedro Salgueiro
>
>
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