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"
39 #include "libguile/validate.h"
40 #include "libguile/continuations.h"
47 scm_t_bits scm_tc16_continuation;
50 continuation_mark (SCM obj)
52 scm_t_contregs *continuation = SCM_CONTREGS (obj);
54 scm_gc_mark (continuation->root);
55 scm_gc_mark (continuation->throw_value);
56 scm_mark_locations (continuation->stack, continuation->num_stack_items);
58 if (continuation->backing_store)
59 scm_mark_locations (continuation->backing_store,
60 continuation->backing_store_size /
61 sizeof (SCM_STACKITEM));
63 return continuation->dynenv;
67 continuation_free (SCM obj)
69 scm_t_contregs *continuation = SCM_CONTREGS (obj);
70 /* stack array size is 1 if num_stack_items is 0. */
71 size_t extra_items = (continuation->num_stack_items > 0)
72 ? (continuation->num_stack_items - 1)
74 size_t bytes_free = sizeof (scm_t_contregs)
75 + extra_items * sizeof (SCM_STACKITEM);
78 scm_gc_free (continuation->backing_store, continuation->backing_store_size,
79 "continuation backing store");
81 scm_gc_free (continuation, bytes_free, "continuation");
86 continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED)
88 scm_t_contregs *continuation = SCM_CONTREGS (obj);
90 scm_puts ("#<continuation ", port);
91 scm_intprint (continuation->num_stack_items, 10, port);
92 scm_puts (" @ ", port);
93 scm_uintprint (SCM_CELL_WORD_1 (obj), 16, port);
98 /* this may return more than once: the first time with the escape
99 procedure, then subsequently with the value to be passed to the
101 #define FUNC_NAME "scm_make_continuation"
103 scm_make_continuation (int *first)
105 scm_i_thread *thread = SCM_I_CURRENT_THREAD;
107 scm_t_contregs *continuation;
111 SCM_FLUSH_REGISTER_WINDOWS;
112 stack_size = scm_stack_size (thread->continuation_base);
113 continuation = scm_gc_malloc (sizeof (scm_t_contregs)
114 + (stack_size - 1) * sizeof (SCM_STACKITEM),
116 continuation->num_stack_items = stack_size;
117 continuation->dynenv = scm_i_dynwinds ();
118 continuation->throw_value = SCM_EOL;
119 continuation->root = thread->continuation_root;
120 continuation->dframe = scm_i_last_debug_frame ();
121 src = thread->continuation_base;
122 SCM_NEWSMOB (cont, scm_tc16_continuation, continuation);
124 #if ! SCM_STACK_GROWS_UP
127 continuation->offset = continuation->stack - src;
128 memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size);
130 *first = !SCM_I_SETJMP (continuation->jmpbuf);
134 continuation->backing_store_size =
135 (char *) scm_ia64_ar_bsp(&continuation->jmpbuf.ctx)
137 (char *) thread->register_backing_store_base;
138 continuation->backing_store = NULL;
139 continuation->backing_store =
140 scm_gc_malloc (continuation->backing_store_size,
141 "continuation backing store");
142 memcpy (continuation->backing_store,
143 (void *) thread->register_backing_store_base,
144 continuation->backing_store_size);
145 #endif /* __ia64__ */
150 SCM ret = continuation->throw_value;
151 continuation->throw_value = SCM_BOOL_F;
158 /* Invoking a continuation proceeds as follows:
160 * - the stack is made large enough for the called continuation
161 * - the old windchain is unwound down to the branching point
162 * - the continuation stack is copied into place
163 * - the windchain is rewound up to the continuation's context
164 * - the continuation is invoked via longjmp (or setcontext)
166 * This order is important so that unwind and rewind handlers are run
167 * with their correct stack.
170 static void scm_dynthrow (SCM, SCM);
172 /* Grow the stack by a fixed amount to provide space to copy in the
173 * continuation. Possibly this function has to be called several times
174 * recursively before enough space is available. Make sure the compiler does
175 * not optimize the growth array away by storing it's address into a global
179 scm_t_bits scm_i_dummy;
182 grow_stack (SCM cont, SCM val)
184 scm_t_bits growth[100];
186 scm_i_dummy = (scm_t_bits) growth;
187 scm_dynthrow (cont, val);
191 /* Copy the continuation stack into the current stack. Calling functions from
192 * within this function is safe, since only stack frames below this function's
193 * own frame are overwritten. Thus, memcpy can be used for best performance.
197 scm_t_contregs *continuation;
202 copy_stack (void *data)
204 copy_stack_data *d = (copy_stack_data *)data;
205 memcpy (d->dst, d->continuation->stack,
206 sizeof (SCM_STACKITEM) * d->continuation->num_stack_items);
208 SCM_I_CURRENT_THREAD->pending_rbs_continuation = d->continuation;
213 copy_stack_and_call (scm_t_contregs *continuation, SCM val,
217 copy_stack_data data;
219 delta = scm_ilength (scm_i_dynwinds ()) - scm_ilength (continuation->dynenv);
220 data.continuation = continuation;
222 scm_i_dowinds (continuation->dynenv, delta, copy_stack, &data);
224 scm_i_set_last_debug_frame (continuation->dframe);
226 continuation->throw_value = val;
227 SCM_I_LONGJMP (continuation->jmpbuf, 1);
232 scm_ia64_longjmp (scm_i_jmp_buf *JB, int VAL)
234 scm_i_thread *t = SCM_I_CURRENT_THREAD;
236 if (t->pending_rbs_continuation)
238 memcpy (t->register_backing_store_base,
239 t->pending_rbs_continuation->backing_store,
240 t->pending_rbs_continuation->backing_store_size);
241 t->pending_rbs_continuation = NULL;
243 setcontext (&JB->ctx);
247 /* Call grow_stack until the stack space is large enough, then, as the current
248 * stack frame might get overwritten, let copy_stack_and_call perform the
249 * actual copying and continuation calling.
252 scm_dynthrow (SCM cont, SCM val)
254 scm_i_thread *thread = SCM_I_CURRENT_THREAD;
255 scm_t_contregs *continuation = SCM_CONTREGS (cont);
256 SCM_STACKITEM *dst = thread->continuation_base;
257 SCM_STACKITEM stack_top_element;
259 if (thread->critical_section_level)
261 fprintf (stderr, "continuation invoked from within critical section.\n");
265 #if SCM_STACK_GROWS_UP
266 if (dst + continuation->num_stack_items >= &stack_top_element)
267 grow_stack (cont, val);
269 dst -= continuation->num_stack_items;
270 if (dst <= &stack_top_element)
271 grow_stack (cont, val);
272 #endif /* def SCM_STACK_GROWS_UP */
274 SCM_FLUSH_REGISTER_WINDOWS;
275 copy_stack_and_call (continuation, val, dst);
280 continuation_apply (SCM cont, SCM args)
281 #define FUNC_NAME "continuation_apply"
283 scm_i_thread *thread = SCM_I_CURRENT_THREAD;
284 scm_t_contregs *continuation = SCM_CONTREGS (cont);
286 if (continuation->root != thread->continuation_root)
289 ("invoking continuation would cross continuation barrier: ~A",
293 scm_dynthrow (cont, scm_values (args));
294 return SCM_UNSPECIFIED; /* not reached */
299 scm_i_with_continuation_barrier (scm_t_catch_body body,
301 scm_t_catch_handler handler,
303 scm_t_catch_handler pre_unwind_handler,
304 void *pre_unwind_handler_data)
306 SCM_STACKITEM stack_item;
307 scm_i_thread *thread = SCM_I_CURRENT_THREAD;
309 SCM_STACKITEM *old_contbase;
310 scm_t_debug_frame *old_lastframe;
313 /* Establish a fresh continuation root.
315 old_controot = thread->continuation_root;
316 old_contbase = thread->continuation_base;
317 old_lastframe = thread->last_debug_frame;
318 thread->continuation_root = scm_cons (thread->handle, old_controot);
319 thread->continuation_base = &stack_item;
320 thread->last_debug_frame = NULL;
322 /* Call FUNC inside a catch all. This is now guaranteed to return
323 directly and exactly once.
325 result = scm_c_catch (SCM_BOOL_T,
327 handler, handler_data,
328 pre_unwind_handler, pre_unwind_handler_data);
330 /* Return to old continuation root.
332 thread->last_debug_frame = old_lastframe;
333 thread->continuation_base = old_contbase;
334 thread->continuation_root = old_controot;
340 void *(*func) (void *);
348 struct c_data *data = (struct c_data *)d;
349 data->result = data->func (data->data);
350 return SCM_UNSPECIFIED;
354 c_handler (void *d, SCM tag, SCM args)
356 struct c_data *data = (struct c_data *)d;
358 return SCM_UNSPECIFIED;
362 scm_c_with_continuation_barrier (void *(*func) (void *), void *data)
364 struct c_data c_data;
367 scm_i_with_continuation_barrier (c_body, &c_data,
369 scm_handle_by_message_noexit, NULL);
370 return c_data.result;
380 struct scm_data *data = (struct scm_data *)d;
381 return scm_call_0 (data->proc);
385 scm_handler (void *d, SCM tag, SCM args)
390 SCM_DEFINE (scm_with_continuation_barrier, "with-continuation-barrier", 1,0,0,
392 "Call @var{proc} and return its result. Do not allow the invocation of\n"
393 "continuations that would leave or enter the dynamic extent of the call\n"
394 "to @code{with-continuation-barrier}. Such an attempt causes an error\n"
397 "Throws (such as errors) that are not caught from within @var{proc} are\n"
398 "caught by @code{with-continuation-barrier}. In that case, a short\n"
399 "message is printed to the current error port and @code{#f} is returned.\n"
401 "Thus, @code{with-continuation-barrier} returns exactly once.\n")
402 #define FUNC_NAME s_scm_with_continuation_barrier
404 struct scm_data scm_data;
405 scm_data.proc = proc;
406 return scm_i_with_continuation_barrier (scm_body, &scm_data,
407 scm_handler, &scm_data,
408 scm_handle_by_message_noexit, NULL);
413 scm_init_continuations ()
415 scm_tc16_continuation = scm_make_smob_type ("continuation", 0);
416 scm_set_smob_mark (scm_tc16_continuation, continuation_mark);
417 scm_set_smob_free (scm_tc16_continuation, continuation_free);
418 scm_set_smob_print (scm_tc16_continuation, continuation_print);
419 scm_set_smob_apply (scm_tc16_continuation, continuation_apply, 0, 0, 1);
420 #include "libguile/continuations.x"