1
/* Copyright (C) 1995,1996,1997,1998,2000,2001, 2003, 2004, 2006 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
22
#include "libguile/_scm.h"
23
#include "libguile/async.h"
24
#include "libguile/smob.h"
25
#include "libguile/alist.h"
26
#include "libguile/eval.h"
27
#include "libguile/eq.h"
28
#include "libguile/dynwind.h"
29
#include "libguile/backtrace.h"
30
#include "libguile/debug.h"
31
#include "libguile/continuations.h"
32
#include "libguile/stackchk.h"
33
#include "libguile/stacks.h"
34
#include "libguile/fluids.h"
35
#include "libguile/ports.h"
36
#include "libguile/lang.h"
37
#include "libguile/validate.h"
38
#include "libguile/throw.h"
39
#include "libguile/init.h"
42
/* the jump buffer data structure */
43
static scm_t_bits tc16_jmpbuffer;
45
#define SCM_JMPBUFP(OBJ) SCM_TYP16_PREDICATE (tc16_jmpbuffer, OBJ)
47
#define JBACTIVE(OBJ) (SCM_CELL_WORD_0 (OBJ) & (1L << 16L))
48
#define ACTIVATEJB(x) \
49
(SCM_SET_CELL_WORD_0 ((x), (SCM_CELL_WORD_0 (x) | (1L << 16L))))
50
#define DEACTIVATEJB(x) \
51
(SCM_SET_CELL_WORD_0 ((x), (SCM_CELL_WORD_0 (x) & ~(1L << 16L))))
53
#define JBJMPBUF(OBJ) ((jmp_buf *) SCM_CELL_WORD_1 (OBJ))
54
#define SETJBJMPBUF(x, v) (SCM_SET_CELL_WORD_1 ((x), (scm_t_bits) (v)))
55
#define SCM_JBDFRAME(x) ((scm_t_debug_frame *) SCM_CELL_WORD_2 (x))
56
#define SCM_SETJBDFRAME(x, v) (SCM_SET_CELL_WORD_2 ((x), (scm_t_bits) (v)))
57
#define SCM_JBPREUNWIND(x) ((struct pre_unwind_data *) SCM_CELL_WORD_3 (x))
58
#define SCM_SETJBPREUNWIND(x, v) (SCM_SET_CELL_WORD_3 ((x), (scm_t_bits) (v)))
61
jmpbuffer_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
63
scm_puts ("#<jmpbuffer ", port);
64
scm_puts (JBACTIVE(exp) ? "(active) " : "(inactive) ", port);
65
scm_uintprint((scm_t_bits) JBJMPBUF (exp), 16, port);
74
SCM_CRITICAL_SECTION_START;
76
SCM_NEWSMOB2 (answer, tc16_jmpbuffer, 0, 0);
77
SETJBJMPBUF(answer, (jmp_buf *)0);
80
SCM_CRITICAL_SECTION_END;
85
/* scm_c_catch (the guts of catch) */
87
struct jmp_buf_and_retval /* use only on the stack, in scm_catch */
89
jmp_buf buf; /* must be first */
94
/* These are the structures we use to store pre-unwind handling (aka
95
"lazy") information for a regular catch, and put on the wind list
96
for a "lazy" catch. They store the pre-unwind handler function to
97
call, and the data pointer to pass through to it. It's not a
98
Scheme closure, but it is a function with data, so the term
99
"closure" is appropriate in its broader sense.
101
(We don't need anything like this to run the normal (post-unwind)
102
catch handler, because the same C frame runs both the body and the
105
struct pre_unwind_data {
106
scm_t_catch_handler handler;
113
/* scm_c_catch is the guts of catch. It handles all the mechanics of
114
setting up a catch target, invoking the catch body, and perhaps
115
invoking the handler if the body does a throw.
117
The function is designed to be usable from C code, but is general
118
enough to implement all the semantics Guile Scheme expects from
121
TAG is the catch tag. Typically, this is a symbol, but this
122
function doesn't actually care about that.
124
BODY is a pointer to a C function which runs the body of the catch;
125
this is the code you can throw from. We call it like this:
128
BODY_DATA is just the BODY_DATA argument we received; we pass it
129
through to BODY as its first argument. The caller can make
130
BODY_DATA point to anything useful that BODY might need.
132
HANDLER is a pointer to a C function to deal with a throw to TAG,
133
should one occur. We call it like this:
134
HANDLER (HANDLER_DATA, THROWN_TAG, THROW_ARGS)
136
HANDLER_DATA is the HANDLER_DATA argument we recevied; it's the
137
same idea as BODY_DATA above.
138
THROWN_TAG is the tag that the user threw to; usually this is
139
TAG, but it could be something else if TAG was #t (i.e., a
140
catch-all), or the user threw to a jmpbuf.
141
THROW_ARGS is the list of arguments the user passed to the THROW
142
function, after the tag.
144
BODY_DATA is just a pointer we pass through to BODY. HANDLER_DATA
145
is just a pointer we pass through to HANDLER. We don't actually
146
use either of those pointers otherwise ourselves. The idea is
147
that, if our caller wants to communicate something to BODY or
148
HANDLER, it can pass a pointer to it as MUMBLE_DATA, which BODY and
149
HANDLER can then use. Think of it as a way to make BODY and
150
HANDLER closures, not just functions; MUMBLE_DATA points to the
153
Of course, it's up to the caller to make sure that any data a
154
MUMBLE_DATA needs is protected from GC. A common way to do this is
155
to make MUMBLE_DATA a pointer to data stored in an automatic
156
structure variable; since the collector must scan the stack for
157
references anyway, this assures that any references in MUMBLE_DATA
161
scm_c_catch (SCM tag,
162
scm_t_catch_body body, void *body_data,
163
scm_t_catch_handler handler, void *handler_data,
164
scm_t_catch_handler pre_unwind_handler, void *pre_unwind_handler_data)
166
struct jmp_buf_and_retval jbr;
169
struct pre_unwind_data pre_unwind;
171
jmpbuf = make_jmpbuf ();
173
scm_i_set_dynwinds (scm_acons (tag, jmpbuf, scm_i_dynwinds ()));
174
SETJBJMPBUF(jmpbuf, &jbr.buf);
175
SCM_SETJBDFRAME(jmpbuf, scm_i_last_debug_frame ());
177
pre_unwind.handler = pre_unwind_handler;
178
pre_unwind.handler_data = pre_unwind_handler_data;
179
pre_unwind.running = 0;
180
pre_unwind.lazy_catch_p = 0;
181
SCM_SETJBPREUNWIND(jmpbuf, &pre_unwind);
183
if (setjmp (jbr.buf))
188
#ifdef STACK_CHECKING
189
scm_stack_checking_enabled_p = SCM_STACK_CHECKING_P;
191
SCM_CRITICAL_SECTION_START;
192
DEACTIVATEJB (jmpbuf);
193
scm_i_set_dynwinds (SCM_CDR (scm_i_dynwinds ()));
194
SCM_CRITICAL_SECTION_END;
195
throw_args = jbr.retval;
196
throw_tag = jbr.throw_tag;
197
jbr.throw_tag = SCM_EOL;
198
jbr.retval = SCM_EOL;
199
answer = handler (handler_data, throw_tag, throw_args);
204
answer = body (body_data);
205
SCM_CRITICAL_SECTION_START;
206
DEACTIVATEJB (jmpbuf);
207
scm_i_set_dynwinds (SCM_CDR (scm_i_dynwinds ()));
208
SCM_CRITICAL_SECTION_END;
214
scm_internal_catch (SCM tag,
215
scm_t_catch_body body, void *body_data,
216
scm_t_catch_handler handler, void *handler_data)
218
return scm_c_catch(tag,
220
handler, handler_data,
226
/* The smob tag for pre_unwind_data smobs. */
227
static scm_t_bits tc16_pre_unwind_data;
229
/* Strictly speaking, we could just pass a zero for our print
230
function, because we don't need to print them. They should never
231
appear in normal data structures, only in the wind list. However,
232
it might be nice for debugging someday... */
234
pre_unwind_data_print (SCM closure, SCM port, scm_print_state *pstate SCM_UNUSED)
236
struct pre_unwind_data *c = (struct pre_unwind_data *) SCM_CELL_WORD_1 (closure);
239
sprintf (buf, "#<pre-unwind-data 0x%lx 0x%lx>",
240
(long) c->handler, (long) c->handler_data);
241
scm_puts (buf, port);
247
/* Given a pointer to a pre_unwind_data structure, return a smob for it,
248
suitable for inclusion in the wind list. ("Ah yes, a Ch�teau
249
Gollombiere '72, non?"). */
251
make_pre_unwind_data (struct pre_unwind_data *c)
253
SCM_RETURN_NEWSMOB (tc16_pre_unwind_data, c);
256
#define SCM_PRE_UNWIND_DATA_P(obj) (SCM_TYP16_PREDICATE (tc16_pre_unwind_data, obj))
259
scm_c_with_throw_handler (SCM tag,
260
scm_t_catch_body body,
262
scm_t_catch_handler handler,
266
SCM pre_unwind, answer;
267
struct pre_unwind_data c;
270
c.handler_data = handler_data;
272
c.lazy_catch_p = lazy_catch_p;
273
pre_unwind = make_pre_unwind_data (&c);
275
SCM_CRITICAL_SECTION_START;
276
scm_i_set_dynwinds (scm_acons (tag, pre_unwind, scm_i_dynwinds ()));
277
SCM_CRITICAL_SECTION_END;
279
answer = (*body) (body_data);
281
SCM_CRITICAL_SECTION_START;
282
scm_i_set_dynwinds (SCM_CDR (scm_i_dynwinds ()));
283
SCM_CRITICAL_SECTION_END;
288
/* Exactly like scm_internal_catch, except:
289
- It does not unwind the stack (this is the major difference).
290
- The handler is not allowed to return. */
292
scm_internal_lazy_catch (SCM tag, scm_t_catch_body body, void *body_data, scm_t_catch_handler handler, void *handler_data)
294
return scm_c_with_throw_handler (tag, body, body_data, handler, handler_data, 1);
298
/* scm_internal_stack_catch
299
Use this one if you want debugging information to be stored in
300
scm_the_last_stack_fluid_var on error. */
303
ss_handler (void *data SCM_UNUSED, SCM tag, SCM throw_args)
306
scm_fluid_set_x (SCM_VARIABLE_REF (scm_the_last_stack_fluid_var),
307
scm_make_stack (SCM_BOOL_T, SCM_EOL));
308
/* Throw the error */
309
return scm_throw (tag, throw_args);
315
scm_t_catch_body body;
320
cwss_body (void *data)
322
struct cwss_data *d = data;
323
return scm_internal_lazy_catch (d->tag, d->body, d->data, ss_handler, NULL);
327
scm_internal_stack_catch (SCM tag,
328
scm_t_catch_body body,
330
scm_t_catch_handler handler,
337
return scm_internal_catch (tag, cwss_body, &d, handler, handler_data);
342
/* body and handler functions for use with any of the above catch variants */
344
/* This is a body function you can pass to scm_internal_catch if you
345
want the body to be like Scheme's `catch' --- a thunk.
347
BODY_DATA is a pointer to a scm_body_thunk_data structure, which
348
contains the Scheme procedure to invoke as the body, and the tag
352
scm_body_thunk (void *body_data)
354
struct scm_body_thunk_data *c = (struct scm_body_thunk_data *) body_data;
356
return scm_call_0 (c->body_proc);
360
/* This is a handler function you can pass to scm_internal_catch if
361
you want the handler to act like Scheme's catch: (throw TAG ARGS ...)
362
applies a handler procedure to (TAG ARGS ...).
364
If the user does a throw to this catch, this function runs a
365
handler procedure written in Scheme. HANDLER_DATA is a pointer to
366
an SCM variable holding the Scheme procedure object to invoke. It
367
ought to be a pointer to an automatic variable (i.e., one living on
368
the stack), or the procedure object should be otherwise protected
371
scm_handle_by_proc (void *handler_data, SCM tag, SCM throw_args)
373
SCM *handler_proc_p = (SCM *) handler_data;
375
return scm_apply_1 (*handler_proc_p, tag, throw_args);
378
/* SCM_HANDLE_BY_PROC_CATCHING_ALL is like SCM_HANDLE_BY_PROC but
379
catches all throws that the handler might emit itself. The handler
380
used for these `secondary' throws is SCM_HANDLE_BY_MESSAGE_NO_EXIT. */
388
hbpca_body (void *body_data)
390
struct hbpca_data *data = (struct hbpca_data *)body_data;
391
return scm_apply_0 (data->proc, data->args);
395
scm_handle_by_proc_catching_all (void *handler_data, SCM tag, SCM throw_args)
397
SCM *handler_proc_p = (SCM *) handler_data;
398
struct hbpca_data data;
399
data.proc = *handler_proc_p;
400
data.args = scm_cons (tag, throw_args);
402
return scm_internal_catch (SCM_BOOL_T,
404
scm_handle_by_message_noexit, NULL);
407
/* Derive the an exit status from the arguments to (quit ...). */
409
scm_exit_status (SCM args)
411
if (!SCM_NULL_OR_NIL_P (args))
413
SCM cqa = SCM_CAR (args);
415
if (scm_is_integer (cqa))
416
return (scm_to_int (cqa));
417
else if (scm_is_false (cqa))
425
handler_message (void *handler_data, SCM tag, SCM args)
427
char *prog_name = (char *) handler_data;
428
SCM p = scm_current_error_port ();
430
if (scm_ilength (args) == 4)
432
SCM stack = scm_make_stack (SCM_BOOL_T, SCM_EOL);
433
SCM subr = SCM_CAR (args);
434
SCM message = SCM_CADR (args);
435
SCM parts = SCM_CADDR (args);
436
SCM rest = SCM_CADDDR (args);
438
if (SCM_BACKTRACE_P && scm_is_true (stack))
442
if (scm_is_eq (tag, scm_arg_type_key)
443
|| scm_is_eq (tag, scm_out_of_range_key))
446
highlights = SCM_EOL;
448
scm_puts ("Backtrace:\n", p);
449
scm_display_backtrace_with_highlights (stack, p,
450
SCM_BOOL_F, SCM_BOOL_F,
454
scm_i_display_error (stack, p, subr, message, parts, rest);
461
scm_puts (prog_name, p);
464
scm_puts ("uncaught throw to ", p);
465
scm_prin1 (tag, p, 0);
467
scm_prin1 (args, p, 1);
473
/* This is a handler function to use if you want scheme to print a
474
message and die. Useful for dealing with throws to uncaught keys
477
At boot time, we establish a catch-all that uses this as its handler.
478
1) If the user wants something different, they can use (catch #t
479
...) to do what they like.
480
2) Outside the context of a read-eval-print loop, there isn't
481
anything else good to do; libguile should not assume the existence
482
of a read-eval-print loop.
483
3) Given that we shouldn't do anything complex, it's much more
484
robust to do it in C code.
486
HANDLER_DATA, if non-zero, is assumed to be a char * pointing to a
487
message header to print; if zero, we use "guile" instead. That
488
text is followed by a colon, then the message described by ARGS. */
490
/* Dirk:FIXME:: The name of the function should make clear that the
491
* application gets terminated.
495
scm_handle_by_message (void *handler_data, SCM tag, SCM args)
497
if (scm_is_true (scm_eq_p (tag, scm_from_locale_symbol ("quit"))))
498
exit (scm_exit_status (args));
500
handler_message (handler_data, tag, args);
501
scm_i_pthread_exit (NULL);
503
/* this point not reached, but suppress gcc warning about no return value
504
in case scm_i_pthread_exit isn't marked as "noreturn" (which seemed not
505
to be the case on cygwin for instance) */
510
/* This is just like scm_handle_by_message, but it doesn't exit; it
511
just returns #f. It's useful in cases where you don't really know
512
enough about the body to handle things in a better way, but don't
513
want to let throws fall off the bottom of the wind list. */
515
scm_handle_by_message_noexit (void *handler_data, SCM tag, SCM args)
517
if (scm_is_true (scm_eq_p (tag, scm_from_locale_symbol ("quit"))))
518
exit (scm_exit_status (args));
520
handler_message (handler_data, tag, args);
527
scm_handle_by_throw (void *handler_data SCM_UNUSED, SCM tag, SCM args)
529
scm_ithrow (tag, args, 1);
530
return SCM_UNSPECIFIED; /* never returns */
535
/* the Scheme-visible CATCH, WITH-THROW-HANDLER and LAZY-CATCH functions */
537
SCM_DEFINE (scm_catch_with_pre_unwind_handler, "catch", 3, 1, 0,
538
(SCM key, SCM thunk, SCM handler, SCM pre_unwind_handler),
539
"Invoke @var{thunk} in the dynamic context of @var{handler} for\n"
540
"exceptions matching @var{key}. If thunk throws to the symbol\n"
541
"@var{key}, then @var{handler} is invoked this way:\n"
543
"(handler key args ...)\n"
546
"@var{key} is a symbol or @code{#t}.\n"
548
"@var{thunk} takes no arguments. If @var{thunk} returns\n"
549
"normally, that is the return value of @code{catch}.\n"
551
"Handler is invoked outside the scope of its own @code{catch}.\n"
552
"If @var{handler} again throws to the same key, a new handler\n"
553
"from further up the call chain is invoked.\n"
555
"If the key is @code{#t}, then a throw to @emph{any} symbol will\n"
556
"match this call to @code{catch}.\n"
558
"If a @var{pre-unwind-handler} is given and @var{thunk} throws\n"
559
"an exception that matches @var{key}, Guile calls the\n"
560
"@var{pre-unwind-handler} before unwinding the dynamic state and\n"
561
"invoking the main @var{handler}. @var{pre-unwind-handler} should\n"
562
"be a procedure with the same signature as @var{handler}, that\n"
563
"is @code{(lambda (key . args))}. It is typically used to save\n"
564
"the stack at the point where the exception occurred, but can also\n"
565
"query other parts of the dynamic state at that point, such as\n"
568
"A @var{pre-unwind-handler} can exit either normally or non-locally.\n"
569
"If it exits normally, Guile unwinds the stack and dynamic context\n"
570
"and then calls the normal (third argument) handler. If it exits\n"
571
"non-locally, that exit determines the continuation.")
572
#define FUNC_NAME s_scm_catch_with_pre_unwind_handler
574
struct scm_body_thunk_data c;
576
SCM_ASSERT (scm_is_symbol (key) || scm_is_eq (key, SCM_BOOL_T),
577
key, SCM_ARG1, FUNC_NAME);
582
/* scm_c_catch takes care of all the mechanics of setting up a catch
583
key; we tell it to call scm_body_thunk to run the body, and
584
scm_handle_by_proc to deal with any throws to this catch. The
585
former receives a pointer to c, telling it how to behave. The
586
latter receives a pointer to HANDLER, so it knows who to
588
return scm_c_catch (key,
590
scm_handle_by_proc, &handler,
591
SCM_UNBNDP (pre_unwind_handler) ? NULL : scm_handle_by_proc,
592
&pre_unwind_handler);
596
/* The following function exists to provide backwards compatibility
597
for the C scm_catch API. Otherwise we could just change
598
"scm_catch_with_pre_unwind_handler" above to "scm_catch". */
600
scm_catch (SCM key, SCM thunk, SCM handler)
602
return scm_catch_with_pre_unwind_handler (key, thunk, handler, SCM_UNDEFINED);
606
SCM_DEFINE (scm_with_throw_handler, "with-throw-handler", 3, 0, 0,
607
(SCM key, SCM thunk, SCM handler),
608
"Add @var{handler} to the dynamic context as a throw handler\n"
609
"for key @var{key}, then invoke @var{thunk}.")
610
#define FUNC_NAME s_scm_with_throw_handler
612
struct scm_body_thunk_data c;
614
SCM_ASSERT (scm_is_symbol (key) || scm_is_eq (key, SCM_BOOL_T),
615
key, SCM_ARG1, FUNC_NAME);
620
/* scm_c_with_throw_handler takes care of the mechanics of setting
621
up a throw handler; we tell it to call scm_body_thunk to run the
622
body, and scm_handle_by_proc to deal with any throws to this
623
handler. The former receives a pointer to c, telling it how to
624
behave. The latter receives a pointer to HANDLER, so it knows
626
return scm_c_with_throw_handler (key,
628
scm_handle_by_proc, &handler,
633
SCM_DEFINE (scm_lazy_catch, "lazy-catch", 3, 0, 0,
634
(SCM key, SCM thunk, SCM handler),
635
"This behaves exactly like @code{catch}, except that it does\n"
636
"not unwind the stack before invoking @var{handler}.\n"
637
"If the @var{handler} procedure returns normally, Guile\n"
638
"rethrows the same exception again to the next innermost catch,\n"
639
"lazy-catch or throw handler. If the @var{handler} exits\n"
640
"non-locally, that exit determines the continuation.")
641
#define FUNC_NAME s_scm_lazy_catch
643
struct scm_body_thunk_data c;
645
SCM_ASSERT (scm_is_symbol (key) || scm_is_eq (key, SCM_BOOL_T),
646
key, SCM_ARG1, FUNC_NAME);
651
/* scm_internal_lazy_catch takes care of all the mechanics of
652
setting up a lazy catch key; we tell it to call scm_body_thunk to
653
run the body, and scm_handle_by_proc to deal with any throws to
654
this catch. The former receives a pointer to c, telling it how
655
to behave. The latter receives a pointer to HANDLER, so it knows
657
return scm_internal_lazy_catch (key,
659
scm_handle_by_proc, &handler);
667
static void toggle_pre_unwind_running (void *data)
669
struct pre_unwind_data *pre_unwind = (struct pre_unwind_data *)data;
670
pre_unwind->running = !pre_unwind->running;
673
SCM_DEFINE (scm_throw, "throw", 1, 0, 1,
675
"Invoke the catch form matching @var{key}, passing @var{args} to the\n"
676
"@var{handler}. \n\n"
677
"@var{key} is a symbol. It will match catches of the same symbol or of\n"
679
"If there is no handler at all, Guile prints an error and then exits.")
680
#define FUNC_NAME s_scm_throw
682
SCM_VALIDATE_SYMBOL (1, key);
683
return scm_ithrow (key, args, 1);
688
scm_ithrow (SCM key, SCM args, int noreturn SCM_UNUSED)
690
SCM jmpbuf = SCM_UNDEFINED;
693
SCM dynpair = SCM_UNDEFINED;
696
if (scm_i_critical_section_level)
698
fprintf (stderr, "throw from within critical section.\n");
704
/* Search the wind list for an appropriate catch.
705
"Waiter, please bring us the wind list." */
706
for (winds = scm_i_dynwinds (); scm_is_pair (winds); winds = SCM_CDR (winds))
708
dynpair = SCM_CAR (winds);
709
if (scm_is_pair (dynpair))
711
SCM this_key = SCM_CAR (dynpair);
713
if (scm_is_eq (this_key, SCM_BOOL_T) || scm_is_eq (this_key, key))
715
jmpbuf = SCM_CDR (dynpair);
717
if (!SCM_PRE_UNWIND_DATA_P (jmpbuf))
721
struct pre_unwind_data *c =
722
(struct pre_unwind_data *) SCM_CELL_WORD_1 (jmpbuf);
730
/* If we didn't find anything, print a message and abort the process
731
right here. If you don't want this, establish a catch-all around
732
any code that might throw up. */
733
if (scm_is_null (winds))
735
scm_handle_by_message (NULL, key, args);
739
/* If the wind list is malformed, bail. */
740
if (!scm_is_pair (winds))
743
for (wind_goal = scm_i_dynwinds ();
744
(!scm_is_pair (SCM_CAR (wind_goal))
745
|| !scm_is_eq (SCM_CDAR (wind_goal), jmpbuf));
746
wind_goal = SCM_CDR (wind_goal))
749
/* Is this a throw handler (or lazy catch)? In a wind list entry
750
for a throw handler or lazy catch, the key is bound to a
751
pre_unwind_data smob, not a jmpbuf. */
752
if (SCM_PRE_UNWIND_DATA_P (jmpbuf))
754
struct pre_unwind_data *c =
755
(struct pre_unwind_data *) SCM_CELL_WORD_1 (jmpbuf);
758
/* For old-style lazy-catch behaviour, we unwind the dynamic
759
context before invoking the handler. */
762
scm_dowinds (wind_goal, (scm_ilength (scm_i_dynwinds ())
763
- scm_ilength (wind_goal)));
764
SCM_CRITICAL_SECTION_START;
765
handle = scm_i_dynwinds ();
766
scm_i_set_dynwinds (SCM_CDR (handle));
767
SCM_CRITICAL_SECTION_END;
770
/* Call the handler, with framing to set the pre-unwind
771
structure's running field while the handler is running, so we
772
can avoid recursing into the same handler again. Note that
773
if the handler returns normally, the running flag stays
774
set until some kind of non-local jump occurs. */
775
scm_dynwind_begin (SCM_F_DYNWIND_REWINDABLE);
776
scm_dynwind_rewind_handler (toggle_pre_unwind_running,
778
SCM_F_WIND_EXPLICITLY);
779
scm_dynwind_unwind_handler (toggle_pre_unwind_running, c, 0);
780
answer = (c->handler) (c->handler_data, key, args);
782
/* There is deliberately no scm_dynwind_end call here. This
783
means that the unwind handler (toggle_pre_unwind_running)
784
stays in place until a non-local exit occurs, and will then
785
reset the pre-unwind structure's running flag. For sample
786
code where this makes a difference, see the "again but with
787
two chained throw handlers" test case in exceptions.test. */
789
/* If the handler returns, rethrow the same key and args. */
793
/* Otherwise, it's a normal catch. */
794
else if (SCM_JMPBUFP (jmpbuf))
796
struct pre_unwind_data * pre_unwind;
797
struct jmp_buf_and_retval * jbr;
799
/* Before unwinding anything, run the pre-unwind handler if
800
there is one, and if it isn't already running. */
801
pre_unwind = SCM_JBPREUNWIND (jmpbuf);
802
if (pre_unwind->handler && !pre_unwind->running)
804
/* Use framing to detect and avoid possible reentry into
805
this handler, which could otherwise cause an infinite
807
scm_dynwind_begin (SCM_F_DYNWIND_REWINDABLE);
808
scm_dynwind_rewind_handler (toggle_pre_unwind_running,
810
SCM_F_WIND_EXPLICITLY);
811
scm_dynwind_unwind_handler (toggle_pre_unwind_running,
813
SCM_F_WIND_EXPLICITLY);
814
(pre_unwind->handler) (pre_unwind->handler_data, key, args);
818
/* Now unwind and jump. */
819
scm_dowinds (wind_goal, (scm_ilength (scm_i_dynwinds ())
820
- scm_ilength (wind_goal)));
821
jbr = (struct jmp_buf_and_retval *)JBJMPBUF (jmpbuf);
822
jbr->throw_tag = key;
824
scm_i_set_last_debug_frame (SCM_JBDFRAME (jmpbuf));
825
longjmp (*JBJMPBUF (jmpbuf), 1);
828
/* Otherwise, it's some random piece of junk. */
837
tc16_jmpbuffer = scm_make_smob_type ("jmpbuffer", 0);
838
scm_set_smob_print (tc16_jmpbuffer, jmpbuffer_print);
840
tc16_pre_unwind_data = scm_make_smob_type ("pre-unwind-data", 0);
841
scm_set_smob_print (tc16_pre_unwind_data, pre_unwind_data_print);
843
#include "libguile/throw.x"
added
removed
libguile/throw.c
