summaryrefslogtreecommitdiff
path: root/libguile/continuations.c
blob: f1124e4307af1a9bd8f1719f6e95238f53851d54 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
/* Copyright (C) 1995,1996,1998,2000,2001 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 "libguile/_scm.h"

#include <string.h>

#include "libguile/root.h"
#include "libguile/stackchk.h"
#include "libguile/smob.h"
#include "libguile/ports.h"
#include "libguile/dynwind.h"
#include "libguile/values.h"

#ifdef DEBUG_EXTENSIONS
#include "libguile/debug.h"
#endif

#include "libguile/validate.h"
#include "libguile/continuations.h"



/* {Continuations}
 */

scm_t_bits scm_tc16_continuation;

static SCM
continuation_mark (SCM obj)
{
  scm_t_contregs *continuation = SCM_CONTREGS (obj);

  scm_gc_mark (continuation->throw_value);
  scm_mark_locations (continuation->stack, continuation->num_stack_items);
#ifdef __ia64__
  if (continuation->backing_store)
    scm_mark_locations (continuation->backing_store, 
                        continuation->backing_store_size / 
                        sizeof (SCM_STACKITEM));
#endif /* __ia64__ */
  return continuation->dynenv;
}

static size_t
continuation_free (SCM obj)
{
  scm_t_contregs *continuation = SCM_CONTREGS (obj);
  /* stack array size is 1 if num_stack_items is 0 (rootcont).  */
  size_t extra_items = (continuation->num_stack_items > 0)
    ? (continuation->num_stack_items - 1)
    : 0;
  size_t bytes_free = sizeof (scm_t_contregs)
    + extra_items * sizeof (SCM_STACKITEM);

#ifdef __ia64__
  scm_gc_free (continuation->backing_store, continuation->backing_store_size,
	       "continuation backing store");
#endif /* __ia64__ */ 
  scm_gc_free (continuation, bytes_free, "continuation");
  return 0;
}

static int
continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED)
{
  scm_t_contregs *continuation = SCM_CONTREGS (obj);

  scm_puts ("#<continuation ", port);
  scm_intprint (continuation->num_stack_items, 10, port);
  scm_puts (" @ ", port);
  scm_intprint (SCM_CELL_WORD_1 (obj), 16, port);
  scm_putc ('>', port);
  return 1;
}

#ifdef __ia64__
/* Extern declaration of getcontext()/setcontext() in order to redefine
   getcontext() since on ia64-linux the second return value indicates whether
   it returned from getcontext() itself or by running setcontext(). */
struct rv
{
  long retval;
  long first_return;
};
extern struct rv getcontext (ucontext_t *);
extern int setcontext (ucontext_t *);
#endif /* __ia64__ */

/* this may return more than once: the first time with the escape
   procedure, then subsequently with the value to be passed to the
   continuation.  */
#define FUNC_NAME "scm_make_continuation"
SCM 
scm_make_continuation (int *first)
{
  volatile SCM cont;
  scm_t_contregs *continuation;
  scm_t_contregs *rootcont = SCM_CONTREGS (scm_rootcont);
  long stack_size;
  SCM_STACKITEM * src;
#ifdef __ia64__
  struct rv rv;
#endif /* __ia64__ */

  SCM_ENTER_A_SECTION;
  SCM_FLUSH_REGISTER_WINDOWS;
  stack_size = scm_stack_size (rootcont->base);
  continuation = scm_gc_malloc (sizeof (scm_t_contregs)
				+ (stack_size - 1) * sizeof (SCM_STACKITEM),
				"continuation");
  continuation->num_stack_items = stack_size;
  continuation->dynenv = scm_dynwinds;
  continuation->throw_value = SCM_EOL;
  continuation->base = src = rootcont->base;
  continuation->seq = rootcont->seq;
#ifdef DEBUG_EXTENSIONS
  continuation->dframe = scm_last_debug_frame;
#endif
  SCM_NEWSMOB (cont, scm_tc16_continuation, continuation);
  SCM_EXIT_A_SECTION;

#if ! SCM_STACK_GROWS_UP
  src -= stack_size;
#endif
  memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size);

#ifdef __ia64__
  rv = getcontext (&continuation->ctx);
  if (rv.first_return)
    {
      continuation->backing_store_size = 
        continuation->ctx.uc_mcontext.sc_ar_bsp - 
        (unsigned long) __libc_ia64_register_backing_store_base;
      continuation->backing_store = NULL;
      continuation->backing_store = 
        scm_gc_malloc (continuation->backing_store_size,
		       "continuation backing store");
      memcpy (continuation->backing_store, 
              (void *) __libc_ia64_register_backing_store_base, 
              continuation->backing_store_size);
      *first = 1;
      return cont;
    }
  else
    {
      SCM ret = continuation->throw_value;
      *first = 0;
      continuation->throw_value = SCM_BOOL_F;
      return ret;
    }
#else /* !__ia64__ */
  if (setjmp (continuation->jmpbuf))
    {
      SCM ret = continuation->throw_value;
      *first = 0;
      continuation->throw_value = SCM_BOOL_F;
      return ret;
    }
  else
    {
      *first = 1;
      return cont;
    }
#endif /* !__ia64__ */
}
#undef FUNC_NAME

static void scm_dynthrow (SCM, SCM);

/* Grow the stack by a fixed amount to provide space to copy in the
 * continuation.  Possibly this function has to be called several times
 * recursively before enough space is available.  Make sure the compiler does
 * not optimize the growth array away by storing it's address into a global
 * variable.
 */

scm_t_bits scm_i_dummy;

static void 
grow_stack (SCM cont, SCM val)
{
  scm_t_bits growth[100];

  scm_i_dummy = (scm_t_bits) growth;
  scm_dynthrow (cont, val);
}


/* Copy the continuation stack into the current stack.  Calling functions from
 * within this function is safe, since only stack frames below this function's
 * own frame are overwritten.  Thus, memcpy can be used for best performance.
 */
static void
copy_stack_and_call (scm_t_contregs *continuation, SCM val, 
		     SCM_STACKITEM * dst)
{
  memcpy (dst, continuation->stack,
	  sizeof (SCM_STACKITEM) * continuation->num_stack_items);

#ifdef DEBUG_EXTENSIONS
  scm_last_debug_frame = continuation->dframe;
#endif

  continuation->throw_value = val;
#ifdef __ia64__
  memcpy ((void *) __libc_ia64_register_backing_store_base,
          continuation->backing_store,
          continuation->backing_store_size);
  setcontext (&continuation->ctx);
#else
  longjmp (continuation->jmpbuf, 1);
#endif
}


/* Call grow_stack until the stack space is large enough, then, as the current
 * stack frame might get overwritten, let copy_stack_and_call perform the
 * actual copying and continuation calling.
 */
static void 
scm_dynthrow (SCM cont, SCM val)
{
  scm_t_contregs *continuation = SCM_CONTREGS (cont);
  SCM_STACKITEM * dst = SCM_BASE (scm_rootcont);
  SCM_STACKITEM stack_top_element;

#if SCM_STACK_GROWS_UP
  if (SCM_PTR_GE (dst + continuation->num_stack_items, &stack_top_element))
    grow_stack (cont, val);
#else
  dst -= continuation->num_stack_items;
  if (dst <= &stack_top_element)
    grow_stack (cont, val);
#endif /* def SCM_STACK_GROWS_UP */

  SCM_FLUSH_REGISTER_WINDOWS;
  copy_stack_and_call (continuation, val, dst);
}


static SCM
continuation_apply (SCM cont, SCM args)
#define FUNC_NAME "continuation_apply"
{
  scm_t_contregs *continuation = SCM_CONTREGS (cont);
  scm_t_contregs *rootcont = SCM_CONTREGS (scm_rootcont);

  if (continuation->seq != rootcont->seq
      /* this base comparison isn't needed */
      || continuation->base != rootcont->base)
    {
      SCM_MISC_ERROR ("continuation from wrong top level: ~S", 
		      scm_list_1 (cont));
    }
  
  scm_dowinds (continuation->dynenv,
	       scm_ilength (scm_dynwinds)
	       - scm_ilength (continuation->dynenv));
  
  scm_dynthrow (cont, scm_values (args));
  return SCM_UNSPECIFIED; /* not reached */
}
#undef FUNC_NAME


void
scm_init_continuations ()
{
  scm_tc16_continuation = scm_make_smob_type ("continuation", 0);
  scm_set_smob_mark (scm_tc16_continuation, continuation_mark);
  scm_set_smob_free (scm_tc16_continuation, continuation_free);
  scm_set_smob_print (scm_tc16_continuation, continuation_print);
  scm_set_smob_apply (scm_tc16_continuation, continuation_apply, 0, 0, 1);
#include "libguile/continuations.x"
}

/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/