Re: implementing curl module with opaque emacs types

[Stephen Leake <stephen_leake@stephe-leake.org>]

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Stephen Leake <stephen_leake@stephe-leake.org> writes:

> Stephen Leake <stephen_leake@stephe-leake.org> writes:
>
>> So let's take a stab at something closer to your approach.
>>
>> I'm not familiar with the idioms for making an opaque type in C; would
>> that just be a pointer to void? something like:
>>
>> typedef void*  Lisp_Object_Ptr;
>
> Here is the list of Emacs functions that curl.c currently uses
>
>     Fprovide
>     SSDATA
>     XSAVE_POINTER
>     builtin_lisp_symbol (for Qnil)
>     defsubr
>     intern
>     make_string
>
> We can either implement these in a new version of emacs_module_api.h/.c,
> or rewrite curl.c to not use them.

Attached is a first attempt at emacs_module_api.h for this. The only
change in curl.c is:

-#include <config.h>
-#include <lisp.h>
+/* #include <config.h> */
+/* #include <lisp.h> */
+#include "emacs_modules_api.h"


This gives compilation errors:

curl.c: In function 'init':
curl.c:113:13: error: 'Scurl_make' undeclared (first use in this function)
   defsubr (&Scurl_make);
             ^
curl.c:113:13: note: each undeclared identifier is reported only once for each function it appears in
curl.c:114:13: error: 'Scurl_fetch_url' undeclared (first use in this function)
   defsubr (&Scurl_fetch_url);
             ^
curl.c:115:13: error: 'Scurl_content' undeclared (first use in this function)
   defsubr (&Scurl_content);
             ^
curl.c:116:13: error: 'Scurl_free' undeclared (first use in this function)
   defsubr (&Scurl_free);
             ^
Makefile:14: recipe for target 'curl.o' failed

This is because I deleted the declaration of 'sname' from the DEFUN
macro, because I couldn't figure out how to implement it simply.

It seems EXFUN is redundant with the first part of DEFUN, so I'm not
sure why the EXFUN statments are in curl.c.

So we either need a lisp wrapper to declare the module functions, with
some way to lookup the EXFUN symbols to set the function values, or we
need to implement a C function (not macro) that creates the struct for
defsubr.

-- 
-- Stephe

[-- Attachment #2: emacs_modules_api.h --]
[-- Type: application/octet-stream, Size: 3889 bytes --]

/* Emacs modules API */

#ifdef WINDOWSNT
# ifdef emacs
   /* compiling emacs */
#  define EMACS_EXPORT  __declspec(dllexport)
# else
   /* compiling a module */
#  define EMACS_EXPORT  __declspec(dllimport)
# endif
#else
  /* non-Windows OS */
# define EMACS_EXPORT __attribute__((visibility ("default")))
#endif

#include <stdint.h>
#include <stdbool.h>

/* lisp.h:87 */
#ifndef EMACS_INT_MAX
# if INTPTR_MAX <= 0
#  error "INTPTR_MAX misconfigured"
# elif INTPTR_MAX <= INT_MAX >> NONPOINTER_BITS && !defined WIDE_EMACS_INT
typedef int EMACS_INT;
typedef unsigned int EMACS_UINT;
#  define EMACS_INT_MAX INT_MAX
#  define pI ""
# elif INTPTR_MAX <= LONG_MAX >> NONPOINTER_BITS && !defined WIDE_EMACS_INT
typedef long int EMACS_INT;
typedef unsigned long EMACS_UINT;
#  define EMACS_INT_MAX LONG_MAX
#  define pI "l"
/* Check versus LLONG_MAX, not LLONG_MAX >> NONPOINTER_BITS.
   In theory this is not safe, but in practice it seems to be OK.  */
# elif INTPTR_MAX <= LLONG_MAX
typedef long long int EMACS_INT;
typedef unsigned long long int EMACS_UINT;
#  define EMACS_INT_MAX LLONG_MAX
#  define pI "ll"
# else
#  error "INTPTR_MAX too large"
# endif
#endif

/* lisp.h:567 */
#ifdef CHECK_LISP_OBJECT_TYPE

typedef struct { EMACS_INT i; } Lisp_Object;

#define LISP_INITIALLY(i) {i}

#undef CHECK_LISP_OBJECT_TYPE
enum CHECK_LISP_OBJECT_TYPE { CHECK_LISP_OBJECT_TYPE = true };
#else /* CHECK_LISP_OBJECT_TYPE */

/* If a struct type is not wanted, define Lisp_Object as just a number.  */

typedef EMACS_INT Lisp_Object;
#define LISP_INITIALLY(i) (i)
enum CHECK_LISP_OBJECT_TYPE { CHECK_LISP_OBJECT_TYPE = false };
#endif /* CHECK_LISP_OBJECT_TYPE */
/* lisp.h:582 */

/* lisp.h:612 */
EMACS_EXPORT bool STRINGP (Lisp_Object);

/* lisp.h:710 */
#define EXFUN(fnname, maxargs) \
  extern Lisp_Object fnname DEFUN_ARGS_ ## maxargs

/* Note that the weird token-substitution semantics of ANSI C makes
   this work for MANY and UNEVALLED.  */
#define DEFUN_ARGS_MANY         (ptrdiff_t, Lisp_Object *)
#define DEFUN_ARGS_UNEVALLED    (Lisp_Object)
#define DEFUN_ARGS_0    (void)
#define DEFUN_ARGS_1    (Lisp_Object)
#define DEFUN_ARGS_2    (Lisp_Object, Lisp_Object)
#define DEFUN_ARGS_3    (Lisp_Object, Lisp_Object, Lisp_Object)
#define DEFUN_ARGS_4    (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object)
#define DEFUN_ARGS_5    (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object, \
                         Lisp_Object)
#define DEFUN_ARGS_6    (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object, \
                         Lisp_Object, Lisp_Object)
#define DEFUN_ARGS_7    (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object, \
                         Lisp_Object, Lisp_Object, Lisp_Object)
#define DEFUN_ARGS_8    (Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object, \
                         Lisp_Object, Lisp_Object, Lisp_Object, Lisp_Object)

/* lisp.h:754 */
/* FIXME: need to define Qt etc, EXFUNs from globals.h */
#define iQnil 0
#define Qnil builtin_lisp_symbol (iQnil)
#define iQt 955
#define Qt builtin_lisp_symbol (iQt)
EXFUN (Fprovide, 2);

/* lisp.h:1070 */
EMACS_EXPORT Lisp_Object builtin_lisp_symbol (int index);

/* lisp.h:1285 */
EMACS_EXPORT unsigned char *SDATA (Lisp_Object string);

EMACS_EXPORT char *SSDATA (Lisp_Object string);

/* lisp.h:2143 */
EMACS_EXPORT void *
XSAVE_POINTER (Lisp_Object obj, int n);

/* lisp.h:2812 */
/* FIXME: not clear how to declare sname here. */
#define DEFUN(lname, fnname, sname, minargs, maxargs, intspec, doc)     \
   Lisp_Object fnname DEFUN_ARGS_ ## maxargs ;\
   Lisp_Object fnname

/* lisp.h:2839 */
struct Lisp_Subr;
EMACS_EXPORT extern void defsubr (struct Lisp_Subr *);

/* lisp.h:3777 */
EMACS_EXPORT extern Lisp_Object make_string (const char *, ptrdiff_t);

/* lisp.h:3882 */
EMACS_EXPORT extern Lisp_Object make_save_ptr (void *);

/* lisp.h:3987 */
Lisp_Object
intern (const char *str);

/* end of file */