1 /* Copyright (C) 1995,1996,1998,2000,2001,2004 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21 #include "libguile/_scm.h"
25 #include "libguile/debug.h"
26 #include "libguile/root.h"
27 #include "libguile/stackchk.h"
28 #include "libguile/smob.h"
29 #include "libguile/ports.h"
30 #include "libguile/dynwind.h"
31 #include "libguile/values.h"
32 #include "libguile/eval.h"
34 #include "libguile/validate.h"
35 #include "libguile/continuations.h"
42 scm_t_bits scm_tc16_continuation
;
45 continuation_mark (SCM obj
)
47 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
49 scm_gc_mark (continuation
->root
);
50 scm_gc_mark (continuation
->throw_value
);
51 scm_mark_locations (continuation
->stack
, continuation
->num_stack_items
);
53 if (continuation
->backing_store
)
54 scm_mark_locations (continuation
->backing_store
,
55 continuation
->backing_store_size
/
56 sizeof (SCM_STACKITEM
));
58 return continuation
->dynenv
;
62 continuation_free (SCM obj
)
64 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
65 /* stack array size is 1 if num_stack_items is 0. */
66 size_t extra_items
= (continuation
->num_stack_items
> 0)
67 ? (continuation
->num_stack_items
- 1)
69 size_t bytes_free
= sizeof (scm_t_contregs
)
70 + extra_items
* sizeof (SCM_STACKITEM
);
73 scm_gc_free (continuation
->backing_store
, continuation
->backing_store_size
,
74 "continuation backing store");
76 scm_gc_free (continuation
, bytes_free
, "continuation");
81 continuation_print (SCM obj
, SCM port
, scm_print_state
*state SCM_UNUSED
)
83 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
85 scm_puts ("#<continuation ", port
);
86 scm_intprint (continuation
->num_stack_items
, 10, port
);
87 scm_puts (" @ ", port
);
88 scm_uintprint (SCM_CELL_WORD_1 (obj
), 16, port
);
94 /* Extern declaration of getcontext()/setcontext() in order to redefine
95 getcontext() since on ia64-linux the second return value indicates whether
96 it returned from getcontext() itself or by running setcontext(). */
102 extern struct rv
ia64_getcontext (ucontext_t
*) __asm__ ("getcontext");
103 #endif /* __ia64__ */
105 /* this may return more than once: the first time with the escape
106 procedure, then subsequently with the value to be passed to the
108 #define FUNC_NAME "scm_make_continuation"
110 scm_make_continuation (int *first
)
112 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
114 scm_t_contregs
*continuation
;
119 #endif /* __ia64__ */
121 SCM_CRITICAL_SECTION_START
;
122 SCM_FLUSH_REGISTER_WINDOWS
;
123 stack_size
= scm_stack_size (thread
->continuation_base
);
124 continuation
= scm_gc_malloc (sizeof (scm_t_contregs
)
125 + (stack_size
- 1) * sizeof (SCM_STACKITEM
),
127 continuation
->num_stack_items
= stack_size
;
128 continuation
->dynenv
= scm_i_dynwinds ();
129 continuation
->throw_value
= SCM_EOL
;
130 continuation
->root
= thread
->continuation_root
;
131 continuation
->dframe
= scm_i_last_debug_frame ();
132 src
= thread
->continuation_base
;
133 SCM_NEWSMOB (cont
, scm_tc16_continuation
, continuation
);
134 SCM_CRITICAL_SECTION_END
;
136 #if ! SCM_STACK_GROWS_UP
139 continuation
->offset
= continuation
->stack
- src
;
140 memcpy (continuation
->stack
, src
, sizeof (SCM_STACKITEM
) * stack_size
);
143 rv
= ia64_getcontext (&continuation
->ctx
);
146 continuation
->backing_store_size
=
147 continuation
->ctx
.uc_mcontext
.sc_ar_bsp
-
148 (unsigned long) __libc_ia64_register_backing_store_base
;
149 continuation
->backing_store
= NULL
;
150 continuation
->backing_store
=
151 scm_gc_malloc (continuation
->backing_store_size
,
152 "continuation backing store");
153 memcpy (continuation
->backing_store
,
154 (void *) __libc_ia64_register_backing_store_base
,
155 continuation
->backing_store_size
);
161 SCM ret
= continuation
->throw_value
;
163 continuation
->throw_value
= SCM_BOOL_F
;
166 #else /* !__ia64__ */
167 if (setjmp (continuation
->jmpbuf
))
169 SCM ret
= continuation
->throw_value
;
171 continuation
->throw_value
= SCM_BOOL_F
;
179 #endif /* !__ia64__ */
184 /* Invoking a continuation proceeds as follows:
186 * - the stack is made large enough for the called continuation
187 * - the old windchain is unwound down to the branching point
188 * - the continuation stack is copied into place
189 * - the windchain is rewound up to the continuation's context
190 * - the continuation is invoked via longjmp (or setcontext)
192 * This order is important so that unwind and rewind handlers are run
193 * with their correct stack.
196 static void scm_dynthrow (SCM
, SCM
);
198 /* Grow the stack by a fixed amount to provide space to copy in the
199 * continuation. Possibly this function has to be called several times
200 * recursively before enough space is available. Make sure the compiler does
201 * not optimize the growth array away by storing it's address into a global
205 scm_t_bits scm_i_dummy
;
208 grow_stack (SCM cont
, SCM val
)
210 scm_t_bits growth
[100];
212 scm_i_dummy
= (scm_t_bits
) growth
;
213 scm_dynthrow (cont
, val
);
217 /* Copy the continuation stack into the current stack. Calling functions from
218 * within this function is safe, since only stack frames below this function's
219 * own frame are overwritten. Thus, memcpy can be used for best performance.
223 scm_t_contregs
*continuation
;
228 copy_stack (void *data
)
230 copy_stack_data
*d
= (copy_stack_data
*)data
;
231 memcpy (d
->dst
, d
->continuation
->stack
,
232 sizeof (SCM_STACKITEM
) * d
->continuation
->num_stack_items
);
236 copy_stack_and_call (scm_t_contregs
*continuation
, SCM val
,
240 copy_stack_data data
;
242 delta
= scm_ilength (scm_i_dynwinds ()) - scm_ilength (continuation
->dynenv
);
243 data
.continuation
= continuation
;
245 scm_i_dowinds (continuation
->dynenv
, delta
, copy_stack
, &data
);
247 scm_i_set_last_debug_frame (continuation
->dframe
);
249 continuation
->throw_value
= val
;
251 memcpy ((void *) __libc_ia64_register_backing_store_base
,
252 continuation
->backing_store
,
253 continuation
->backing_store_size
);
254 setcontext (&continuation
->ctx
);
256 longjmp (continuation
->jmpbuf
, 1);
260 /* Call grow_stack until the stack space is large enough, then, as the current
261 * stack frame might get overwritten, let copy_stack_and_call perform the
262 * actual copying and continuation calling.
265 scm_dynthrow (SCM cont
, SCM val
)
267 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
268 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
269 SCM_STACKITEM
*dst
= thread
->continuation_base
;
270 SCM_STACKITEM stack_top_element
;
272 #if SCM_STACK_GROWS_UP
273 if (dst
+ continuation
->num_stack_items
>= &stack_top_element
)
274 grow_stack (cont
, val
);
276 dst
-= continuation
->num_stack_items
;
277 if (dst
<= &stack_top_element
)
278 grow_stack (cont
, val
);
279 #endif /* def SCM_STACK_GROWS_UP */
281 SCM_FLUSH_REGISTER_WINDOWS
;
282 copy_stack_and_call (continuation
, val
, dst
);
287 continuation_apply (SCM cont
, SCM args
)
288 #define FUNC_NAME "continuation_apply"
290 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
291 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
293 if (continuation
->root
!= thread
->continuation_root
)
296 ("invoking continuation would cross continuation barrier: ~A",
300 scm_dynthrow (cont
, scm_values (args
));
301 return SCM_UNSPECIFIED
; /* not reached */
306 scm_i_with_continuation_barrier (scm_t_catch_body body
,
308 scm_t_catch_handler handler
,
311 SCM_STACKITEM stack_item
;
312 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
314 SCM_STACKITEM
*old_contbase
;
315 scm_t_debug_frame
*old_lastframe
;
318 /* Establish a fresh continuation root.
320 old_controot
= thread
->continuation_root
;
321 old_contbase
= thread
->continuation_base
;
322 old_lastframe
= thread
->last_debug_frame
;
323 thread
->continuation_root
= scm_cons (thread
->handle
, old_controot
);
324 thread
->continuation_base
= &stack_item
;
325 thread
->last_debug_frame
= NULL
;
327 /* Call FUNC inside a catch all. This is now guaranteed to return
328 directly and exactly once.
330 result
= scm_internal_catch (SCM_BOOL_T
,
332 handler
, 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
;
361 scm_handle_by_message_noexit (NULL
, tag
, args
);
363 return SCM_UNSPECIFIED
;
367 scm_c_with_continuation_barrier (void *(*func
) (void *), void *data
)
369 struct c_data c_data
;
372 scm_i_with_continuation_barrier (c_body
, &c_data
,
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
)
391 scm_handle_by_message_noexit (NULL
, tag
, args
);
395 SCM_DEFINE (scm_with_continuation_barrier
, "with-continuation-barrier", 1,0,0,
397 "Call @var{proc} and return its result. Do not allow the invocation of\n"
398 "continuations that would leave or enter the dynamic extent of the call\n"
399 "to @code{with-continuation-barrier}. Such an attempt causes an error\n"
402 "Throws (such as errors) that are not caught from within @var{proc} are\n"
403 "caught by @code{with-continuation-barrier}. In that case, a short\n"
404 "message is printed to the current error port and @code{#f} is returned.\n"
406 "Thus, @code{with-continuation-barrier} returns exactly once.\n")
407 #define FUNC_NAME s_scm_with_continuation_barrier
409 struct scm_data scm_data
;
410 scm_data
.proc
= proc
;
411 return scm_i_with_continuation_barrier (scm_body
, &scm_data
,
412 scm_handler
, &scm_data
);
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"