[PPL-devel] gprolog.h

26 Oct 2001


      Hi there,
I am interfacing a C++ library to GNU Prolog and I have encountered
a couple of problems.  The first is due to the fact that gprolog.h
uses a the C++ reserved identifier `template'.  It does that at line
639:
char *M_Mktemp(char *template);
Notice that this problem is not solved by replacing
#include <gprolog.h>
with
extern "C" {
#include <gprolog.h>
}
One may indeed resort to the ugly
extern "C" {
#define template templ
#include <gprolog.h>
#undef template
}
but I believe avoiding using any C++ reserved identifier is
a much better solution.  While we are at it, we may wish to
make the C++ user's life a bit simpler by enclosing gprolog.h
withing
#ifdef __cplusplus
extern "C" {
#endif
and
#ifdef __cplusplus
}
#endif
The header gprolog.h has the multiple inclusion guard
#ifndef _GP_CONFIG_H
#define _GP_CONFIG_H
...
#endif
but the guard's #endif is, in the case of gprolog.h
NOT at the end of the file (why?).
As a result, if gprolog.h is included twice you get
tons of redefinition errors.  Can this be fixed?
The last problem concerns the installation of gprolog.h:
it is not put in any path where C/C++ compilers would look
for it.  While it is OK to have it in
$prefix/gprolog-1.2.8/include/gprolog.h
it would be handy if the installation procedure could
set up a symbolic link to it in, say,
$prefix/include/gprolog.h
(unless the user explicitely requests something else, of course).
I enclose a patch to gprolog.h for the template, C++ and inclusion
guard problems.
All the best,
Roberto
-- 
Roberto Bagnara
Computer Science Group
Department of Mathematics, University of Parma, Italy
http://www.cs.unipr.it/~bagnara/
mailto:bagnara@cs.unipr.it

*** gprolog.h.~1~	Fri Oct 26 11:14:03 2001
--- gprolog.h	Fri Oct 26 11:57:09 2001
***************
*** 25,30 ****
--- 25,35 ----
  /* $Id: headers.h,v 1.3 2001/01/23 11:38:20 diaz Exp $ */
  #ifndef _GP_CONFIG_H
  #define _GP_CONFIG_H
+ 
+ #ifdef __cplusplus
+ extern "C" {
+ #endif
+ 
  #define HAVE_TERMIOS_H 1
  #define HAVE_MALLOC_H 1
  #define HAVE_MMAP 1
***************
*** 143,149 ****
  #define FC
  #endif
  #endif /* !_ARCH_DEP_H */
- #endif /* !_GP_CONFIG_H */
  #define MAX_OBJECT                 1024
  #define START_PRED_TBL_SIZE        4096
  #define START_OPER_TBL_SIZE        1024
--- 148,153 ----
***************
*** 636,642 ****
  int M_Spawn_Redirect(char *arg[], int detach,
    	     FILE **f_in, FILE **f_out, FILE **f_err);
  int M_Get_Status(int pid);
! char *M_Mktemp(char *template);
  char *M_Tempnam(char *dir, char *pfx);
  #define   DBGPRINTF             printf
  void Init_Machine(void);
--- 640,646 ----
  int M_Spawn_Redirect(char *arg[], int detach,
    	     FILE **f_in, FILE **f_out, FILE **f_err);
  int M_Get_Status(int pid);
! char *M_Mktemp(char *templ);
  char *M_Tempnam(char *dir, char *pfx);
  #define   DBGPRINTF             printf
  void Init_Machine(void);
***************
*** 2324,2326 ****
--- 2328,2336 ----
  void Full_Max_Cst_Var(Range *z, int a, Range *x);
  void Full_Min_Cst_Var(Range *z, int a, Range *x);
  #endif /* NO_USE_FD_SOLVER */
+ 
+ #ifdef __cplusplus
+ }
+ #endif
+ 
+ #endif /* !_GP_CONFIG_H */