1 /* Copyright (C) 1995,1996,1998,2000,2001,2004, 2006, 2008 Free Software Foundation, Inc.
3 * This library is free software; you can redistribute it and/or
4 * modify it under the terms of the GNU Lesser General Public
5 * License as published by the Free Software Foundation; either
6 * version 2.1 of the License, or (at your option) any later version.
8 * This library is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * Lesser General Public License for more details.
13 * You should have received a copy of the GNU Lesser General Public
14 * License along with this library; if not, write to the Free Software
15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "libguile/_scm.h"
29 #include "libguile/async.h"
30 #include "libguile/debug.h"
31 #include "libguile/root.h"
32 #include "libguile/stackchk.h"
33 #include "libguile/smob.h"
34 #include "libguile/ports.h"
35 #include "libguile/dynwind.h"
36 #include "libguile/values.h"
37 #include "libguile/eval.h"
38 #include "libguile/vm.h"
40 #include "libguile/validate.h"
41 #include "libguile/continuations.h"
48 scm_t_bits scm_tc16_continuation
;
51 continuation_mark (SCM obj
)
53 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
55 scm_gc_mark (continuation
->root
);
56 scm_gc_mark (continuation
->throw_value
);
57 scm_gc_mark (continuation
->vm_conts
);
58 scm_mark_locations (continuation
->stack
, continuation
->num_stack_items
);
60 if (continuation
->backing_store
)
61 scm_mark_locations (continuation
->backing_store
,
62 continuation
->backing_store_size
/
63 sizeof (SCM_STACKITEM
));
65 return continuation
->dynenv
;
69 continuation_free (SCM obj
)
71 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
72 /* stack array size is 1 if num_stack_items is 0. */
73 size_t extra_items
= (continuation
->num_stack_items
> 0)
74 ? (continuation
->num_stack_items
- 1)
76 size_t bytes_free
= sizeof (scm_t_contregs
)
77 + extra_items
* sizeof (SCM_STACKITEM
);
80 scm_gc_free (continuation
->backing_store
, continuation
->backing_store_size
,
81 "continuation backing store");
83 scm_gc_free (continuation
, bytes_free
, "continuation");
88 continuation_print (SCM obj
, SCM port
, scm_print_state
*state SCM_UNUSED
)
90 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
92 scm_puts ("#<continuation ", port
);
93 scm_intprint (continuation
->num_stack_items
, 10, port
);
94 scm_puts (" @ ", port
);
95 scm_uintprint (SCM_CELL_WORD_1 (obj
), 16, port
);
100 /* this may return more than once: the first time with the escape
101 procedure, then subsequently with the value to be passed to the
103 #define FUNC_NAME "scm_make_continuation"
105 scm_make_continuation (int *first
)
107 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
109 scm_t_contregs
*continuation
;
113 SCM_FLUSH_REGISTER_WINDOWS
;
114 stack_size
= scm_stack_size (thread
->continuation_base
);
115 continuation
= scm_gc_malloc (sizeof (scm_t_contregs
)
116 + (stack_size
- 1) * sizeof (SCM_STACKITEM
),
118 continuation
->num_stack_items
= stack_size
;
119 continuation
->dynenv
= scm_i_dynwinds ();
120 continuation
->throw_value
= SCM_EOL
;
121 continuation
->root
= thread
->continuation_root
;
122 continuation
->dframe
= scm_i_last_debug_frame ();
123 src
= thread
->continuation_base
;
124 SCM_NEWSMOB (cont
, scm_tc16_continuation
, continuation
);
126 #if ! SCM_STACK_GROWS_UP
129 continuation
->offset
= continuation
->stack
- src
;
130 memcpy (continuation
->stack
, src
, sizeof (SCM_STACKITEM
) * stack_size
);
131 continuation
->vm_conts
= scm_vm_capture_continuations ();
133 *first
= !setjmp (continuation
->jmpbuf
);
137 continuation
->backing_store_size
=
138 (char *) scm_ia64_ar_bsp(&continuation
->jmpbuf
.ctx
)
140 (char *) thread
->register_backing_store_base
;
141 continuation
->backing_store
= NULL
;
142 continuation
->backing_store
=
143 scm_gc_malloc (continuation
->backing_store_size
,
144 "continuation backing store");
145 memcpy (continuation
->backing_store
,
146 (void *) thread
->register_backing_store_base
,
147 continuation
->backing_store_size
);
148 #endif /* __ia64__ */
153 SCM ret
= continuation
->throw_value
;
154 continuation
->throw_value
= SCM_BOOL_F
;
161 /* Invoking a continuation proceeds as follows:
163 * - the stack is made large enough for the called continuation
164 * - the old windchain is unwound down to the branching point
165 * - the continuation stack is copied into place
166 * - the windchain is rewound up to the continuation's context
167 * - the continuation is invoked via longjmp (or setcontext)
169 * This order is important so that unwind and rewind handlers are run
170 * with their correct stack.
173 static void scm_dynthrow (SCM
, SCM
);
175 /* Grow the stack by a fixed amount to provide space to copy in the
176 * continuation. Possibly this function has to be called several times
177 * recursively before enough space is available. Make sure the compiler does
178 * not optimize the growth array away by storing it's address into a global
182 scm_t_bits scm_i_dummy
;
185 grow_stack (SCM cont
, SCM val
)
187 scm_t_bits growth
[100];
189 scm_i_dummy
= (scm_t_bits
) growth
;
190 scm_dynthrow (cont
, val
);
194 /* Copy the continuation stack into the current stack. Calling functions from
195 * within this function is safe, since only stack frames below this function's
196 * own frame are overwritten. Thus, memcpy can be used for best performance.
200 scm_t_contregs
*continuation
;
205 copy_stack (void *data
)
207 copy_stack_data
*d
= (copy_stack_data
*)data
;
208 memcpy (d
->dst
, d
->continuation
->stack
,
209 sizeof (SCM_STACKITEM
) * d
->continuation
->num_stack_items
);
210 scm_vm_reinstate_continuations (d
->continuation
->vm_conts
);
212 SCM_I_CURRENT_THREAD
->pending_rbs_continuation
= d
->continuation
;
217 copy_stack_and_call (scm_t_contregs
*continuation
, SCM val
,
221 copy_stack_data data
;
223 delta
= scm_ilength (scm_i_dynwinds ()) - scm_ilength (continuation
->dynenv
);
224 data
.continuation
= continuation
;
226 scm_i_dowinds (continuation
->dynenv
, delta
, copy_stack
, &data
);
228 scm_i_set_last_debug_frame (continuation
->dframe
);
230 continuation
->throw_value
= val
;
231 longjmp (continuation
->jmpbuf
, 1);
236 scm_ia64_longjmp (jmp_buf *JB
, int VAL
)
238 scm_i_thread
*t
= SCM_I_CURRENT_THREAD
;
240 if (t
->pending_rbs_continuation
)
242 memcpy (t
->register_backing_store_base
,
243 t
->pending_rbs_continuation
->backing_store
,
244 t
->pending_rbs_continuation
->backing_store_size
);
245 t
->pending_rbs_continuation
= NULL
;
247 setcontext (&JB
->ctx
);
251 /* Call grow_stack until the stack space is large enough, then, as the current
252 * stack frame might get overwritten, let copy_stack_and_call perform the
253 * actual copying and continuation calling.
256 scm_dynthrow (SCM cont
, SCM val
)
258 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
259 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
260 SCM_STACKITEM
*dst
= thread
->continuation_base
;
261 SCM_STACKITEM stack_top_element
;
263 if (scm_i_critical_section_level
)
265 fprintf (stderr
, "continuation invoked from within critical section.\n");
269 #if SCM_STACK_GROWS_UP
270 if (dst
+ continuation
->num_stack_items
>= &stack_top_element
)
271 grow_stack (cont
, val
);
273 dst
-= continuation
->num_stack_items
;
274 if (dst
<= &stack_top_element
)
275 grow_stack (cont
, val
);
276 #endif /* def SCM_STACK_GROWS_UP */
278 SCM_FLUSH_REGISTER_WINDOWS
;
279 copy_stack_and_call (continuation
, val
, dst
);
284 continuation_apply (SCM cont
, SCM args
)
285 #define FUNC_NAME "continuation_apply"
287 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
288 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
290 if (continuation
->root
!= thread
->continuation_root
)
293 ("invoking continuation would cross continuation barrier: ~A",
297 scm_dynthrow (cont
, scm_values (args
));
298 return SCM_UNSPECIFIED
; /* not reached */
303 scm_i_with_continuation_barrier (scm_t_catch_body body
,
305 scm_t_catch_handler handler
,
307 scm_t_catch_handler pre_unwind_handler
,
308 void *pre_unwind_handler_data
)
310 SCM_STACKITEM stack_item
;
311 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
313 SCM_STACKITEM
*old_contbase
;
314 scm_t_debug_frame
*old_lastframe
;
317 /* Establish a fresh continuation root.
319 old_controot
= thread
->continuation_root
;
320 old_contbase
= thread
->continuation_base
;
321 old_lastframe
= thread
->last_debug_frame
;
322 thread
->continuation_root
= scm_cons (thread
->handle
, old_controot
);
323 thread
->continuation_base
= &stack_item
;
324 thread
->last_debug_frame
= NULL
;
326 /* Call FUNC inside a catch all. This is now guaranteed to return
327 directly and exactly once.
329 result
= scm_c_catch (SCM_BOOL_T
,
331 handler
, handler_data
,
332 pre_unwind_handler
, pre_unwind_handler_data
);
334 /* Return to old continuation root.
336 thread
->last_debug_frame
= old_lastframe
;
337 thread
->continuation_base
= old_contbase
;
338 thread
->continuation_root
= old_controot
;
344 void *(*func
) (void *);
352 struct c_data
*data
= (struct c_data
*)d
;
353 data
->result
= data
->func (data
->data
);
354 return SCM_UNSPECIFIED
;
358 c_handler (void *d
, SCM tag
, SCM args
)
360 struct c_data
*data
= (struct c_data
*)d
;
362 return SCM_UNSPECIFIED
;
366 scm_c_with_continuation_barrier (void *(*func
) (void *), void *data
)
368 struct c_data c_data
;
371 scm_i_with_continuation_barrier (c_body
, &c_data
,
373 scm_handle_by_message_noexit
, NULL
);
374 return c_data
.result
;
384 struct scm_data
*data
= (struct scm_data
*)d
;
385 return scm_call_0 (data
->proc
);
389 scm_handler (void *d
, SCM tag
, SCM args
)
394 SCM_DEFINE (scm_with_continuation_barrier
, "with-continuation-barrier", 1,0,0,
396 "Call @var{proc} and return its result. Do not allow the invocation of\n"
397 "continuations that would leave or enter the dynamic extent of the call\n"
398 "to @code{with-continuation-barrier}. Such an attempt causes an error\n"
401 "Throws (such as errors) that are not caught from within @var{proc} are\n"
402 "caught by @code{with-continuation-barrier}. In that case, a short\n"
403 "message is printed to the current error port and @code{#f} is returned.\n"
405 "Thus, @code{with-continuation-barrier} returns exactly once.\n")
406 #define FUNC_NAME s_scm_with_continuation_barrier
408 struct scm_data scm_data
;
409 scm_data
.proc
= proc
;
410 return scm_i_with_continuation_barrier (scm_body
, &scm_data
,
411 scm_handler
, &scm_data
,
412 scm_handle_by_message_noexit
, NULL
);
417 scm_init_continuations ()
419 scm_tc16_continuation
= scm_make_smob_type ("continuation", 0);
420 scm_set_smob_mark (scm_tc16_continuation
, continuation_mark
);
421 scm_set_smob_free (scm_tc16_continuation
, continuation_free
);
422 scm_set_smob_print (scm_tc16_continuation
, continuation_print
);
423 scm_set_smob_apply (scm_tc16_continuation
, continuation_apply
, 0, 0, 1);
424 #include "libguile/continuations.x"