guile/libguile/root.c

/*	Copyright (C) 1995,1996 Free Software Foundation, Inc.
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307 USA
 *
 * As a special exception, the Free Software Foundation gives permission
 * for additional uses of the text contained in its release of GUILE.
 *
 * The exception is that, if you link the GUILE library with other files
 * to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the GUILE library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the
 * Free Software Foundation under the name GUILE.  If you copy
 * code from other Free Software Foundation releases into a copy of
 * GUILE, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for GUILE, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.  */


#include <stdio.h>
#include "_scm.h"
#include "stackchk.h"
#include "dynwind.h"
#include "eval.h"
#include "genio.h"
#include "smob.h"
#include "pairs.h"
#include "throw.h"

#include "root.h"


SCM scm_sys_protects[SCM_NUM_PROTECTS];

long scm_tc16_root;

#ifndef USE_THREADS
struct scm_root_state *scm_root;
#endif



static SCM mark_root SCM_P ((SCM));

static SCM
mark_root (root)
     SCM root;
{
  scm_root_state *s = SCM_ROOT_STATE (root);
  SCM_SETGC8MARK (root);
  scm_gc_mark (s->rootcont);
  scm_gc_mark (s->dynwinds);
  scm_gc_mark (s->continuation_stack);
  scm_gc_mark (s->continuation_stack_ptr);
  scm_gc_mark (s->progargs);
  scm_gc_mark (s->exitval);
  scm_gc_mark (s->cur_inp);
  scm_gc_mark (s->cur_outp);
  scm_gc_mark (s->cur_errp);
  scm_gc_mark (s->def_inp);
  scm_gc_mark (s->def_outp);
  scm_gc_mark (s->def_errp);
  scm_gc_mark (s->top_level_lookup_closure_var);
  scm_gc_mark (s->system_transformer);
  scm_gc_mark (s->the_last_stack_var);
  return SCM_ROOT_STATE (root) -> parent;
}

static scm_sizet free_root SCM_P ((SCM));

static scm_sizet
free_root (root)
     SCM root;
{
  scm_must_free ((char *) SCM_ROOT_STATE (root));
  return sizeof (scm_root_state);
}

static int print_root SCM_P ((SCM exp, SCM port, scm_print_state *pstate));

static int
print_root (exp, port, pstate)
     SCM exp;
     SCM port;
     scm_print_state *pstate;
{
  scm_gen_puts (scm_regular_string, "#<root ", port);
  scm_intprint(SCM_SEQ (SCM_ROOT_STATE (exp) -> rootcont), 16, port);
  scm_gen_putc('>', port);
  return 1;
}

static scm_smobfuns root_smob =
{
  mark_root,
  free_root,
  print_root,
  0
};



SCM
scm_make_root (parent)
     SCM parent;
{
  SCM root;
  scm_root_state *root_state;

  root_state = (scm_root_state *) scm_must_malloc (sizeof (scm_root_state),
						   "scm_make_root");
  if (SCM_NIMP (parent) && SCM_ROOTP (parent))
    {
      memcpy (root_state, SCM_ROOT_STATE (parent), sizeof (scm_root_state));
      root_state->parent = parent;
    }
  else
    {
      root_state->parent = SCM_BOOL_F;
    }
  SCM_NEWCELL (root);
  SCM_REDEFER_INTS;
  SCM_SETCAR (root, scm_tc16_root);
  SCM_SETCDR (root, root_state);
  root_state->handle = root;
  SCM_REALLOW_INTS;
  return root;
}

/* {call-with-dynamic-root}
 *
 * Suspending the current thread to evaluate a thunk on the
 * same C stack but under a new root.
 *
 * Calls to call-with-dynamic-root return exactly once (unless
 * the process is somehow exitted).
 */

/* Some questions about cwdr:

   Couldn't the body just be a closure?  Do we really need to pass
   args through to it?

   The semantics are a lot like catch's; in fact, we call
   scm_internal_catch to take care of that part of things.  Wouldn't
   it be cleaner to say that uncaught throws just disappear into the
   ether (or print a message to stderr), and let the caller use catch
   themselves if they want to?

   -JimB */

#if 0
SCM scm_exitval;		/* INUM with return value */
#endif
static int n_dynamic_roots = 0;


/* cwdr fills out one of these structures, and then passes a pointer
   to it through scm_internal_catch to the cwdr_body function, to tell
   it how to behave.

   A cwdr is a lot like a catch, except there is no tag (all
   exceptions are caught), and the body procedure takes the arguments
   passed to cwdr as A1 and ARGS.  */

struct cwdr_body_data {
  /* Arguments to pass to the cwdr body function.  */
  SCM a1, args;

  /* Scheme procedure to use as body of cwdr.  */
  SCM body_proc;

  /* Scheme handler function to establish.  */
  SCM handler;
};


/* Invoke the body of a cwdr, assuming that the throw handler has
   already been set up.  DATA points to a struct set up by cwdr that
   says what proc to call, and what args to apply it to.

   With a little thought, we could replace this with scm_body_thunk,
   but I don't want to mess with that at the moment.  */
static SCM
cwdr_inner_body (void *data, SCM jmpbuf)
{
  struct cwdr_body_data *c = (struct cwdr_body_data *) data;

  return scm_apply (c->body_proc, c->a1, c->args);
}


/* Invoke the body of a cwdr, assuming that the last-ditch handler has
   been established.  The structure DATA points to must live on the
   stack, or else it won't be found by the GC.  Establish the user's
   handler, and pass control to cwdr_inner_body, which will invoke the
   users' body.  Maybe the user has a nice body.  */
static SCM
cwdr_outer_body (void *data, SCM jmpbuf)
{
  struct cwdr_body_data *c = (struct cwdr_body_data *) data;

  return scm_internal_catch (SCM_BOOL_T,
			     cwdr_inner_body, c,
			     scm_handle_by_proc, &c->handler);
}

/* This is the basic code for new root creation.
 *
 * WARNING!  The order of actions in this routine is in many ways
 * critical.  E. g., it is essential that an error doesn't leave Guile
 * in a messed up state.  */

static SCM 
cwdr (SCM proc, SCM a1, SCM args, SCM handler, SCM_STACKITEM *stack_start)
{
  int old_ints_disabled = scm_ints_disabled;
  SCM old_rootcont, old_winds;
  SCM answer;

  /* Create a fresh root continuation.
   */
  {
    SCM new_rootcont;
    SCM_NEWCELL (new_rootcont);
    SCM_REDEFER_INTS;
    SCM_SETJMPBUF (new_rootcont,
		   scm_must_malloc ((long) sizeof (scm_contregs),
				    "inferior root continuation"));
    SCM_SETCAR (new_rootcont, scm_tc7_contin);
    SCM_DYNENV (new_rootcont) = SCM_EOL;
    SCM_BASE (new_rootcont) = stack_start;
    SCM_SEQ (new_rootcont) = ++n_dynamic_roots;
#ifdef DEBUG_EXTENSIONS
    SCM_DFRAME (new_rootcont) = 0;
#endif
    old_rootcont = scm_rootcont;
    scm_rootcont = new_rootcont;
    SCM_REALLOW_INTS;
  }

  /* Exit caller's dynamic state.
   */
  old_winds = scm_dynwinds;
  scm_dowinds (SCM_EOL, scm_ilength (scm_dynwinds));
#ifdef DEBUG_EXTENSIONS
  SCM_DFRAME (old_rootcont) = scm_last_debug_frame;
  scm_last_debug_frame = 0;
#endif
  
  /* Catch absolutely all errors.  We actually use
     scm_handle_by_message_noexit here, and then install HANDLER in
     cwdr_outer_body, because HANDLER might encounter errors itself.  */
  {
    struct cwdr_body_data c;

    c.a1 = a1;
    c.args = args;
    c.body_proc = proc;
    c.handler = handler;

    answer = scm_internal_catch (SCM_BOOL_T,
				 cwdr_outer_body, &c,
				 scm_handle_by_message_noexit, 0);
  }
  
  scm_dowinds (old_winds, - scm_ilength (old_winds));
  SCM_REDEFER_INTS;
#ifdef DEBUG_EXTENSIONS
  scm_last_debug_frame = SCM_DFRAME (old_rootcont);
#endif
  scm_rootcont = old_rootcont;
  SCM_REALLOW_INTS;
  scm_ints_disabled = old_ints_disabled;
  return answer;
}


SCM_PROC(s_call_with_dynamic_root, "call-with-dynamic-root", 2, 0, 0, scm_call_with_dynamic_root);
SCM
scm_call_with_dynamic_root (thunk, handler)
     SCM thunk;
     SCM handler;
{
  SCM_STACKITEM stack_place;

  return cwdr (thunk, SCM_EOL, SCM_EOL, handler, &stack_place);
}

SCM_PROC(s_dynamic_root, "dynamic-root", 0, 0, 0, scm_dynamic_root);
SCM
scm_dynamic_root ()
{
  return scm_ulong2num (SCM_SEQ (scm_root->rootcont));
}

SCM
scm_apply_with_dynamic_root (proc, a1, args, handler)
     SCM proc;
     SCM a1;
     SCM args;
     SCM handler;
{
  SCM_STACKITEM stack_place;
  return cwdr (proc, a1, args, handler, &stack_place);
}



/* Call thunk(closure) underneath a top-level error handler.
 * If an error occurs, pass the exitval through err_filter and return it.
 * If no error occurs, return the value of thunk.
 */


#ifdef _UNICOS
typedef int setjmp_type;
#else
typedef long setjmp_type;
#endif



SCM
scm_call_catching_errors (thunk, err_filter, closure)
     SCM (*thunk)();
     SCM (*err_filter)();
     void *closure;
{
  SCM answer;
  setjmp_type i;
#ifdef DEBUG_EXTENSIONS
  SCM_DFRAME (scm_rootcont) = scm_last_debug_frame;
#endif
  i = setjmp (SCM_JMPBUF (scm_rootcont));
  scm_stack_checking_enabled_p = SCM_STACK_CHECKING_P;
  if (!i)
    {
      scm_gc_heap_lock = 0;
      answer = thunk (closure);
    }
  else
    {
      scm_gc_heap_lock = 1;
      answer = err_filter (scm_exitval, closure);
    }
  return answer;
}

void
scm_init_root ()
{
  scm_tc16_root = scm_newsmob (&root_smob);
#include "root.x"
}