1 /* Copyright (C) 1995,1996,1998,2000,2001,2004, 2006, 2008, 2009, 2010, 2011, 2012 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 License
5 * as published by the Free Software Foundation; either version 3 of
6 * the License, or (at your option) any later version.
8 * This library is distributed in the hope that it will be useful, but
9 * 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
25 #include "libguile/_scm.h"
31 #include "libguile/async.h"
32 #include "libguile/debug.h"
33 #include "libguile/root.h"
34 #include "libguile/stackchk.h"
35 #include "libguile/smob.h"
36 #include "libguile/ports.h"
37 #include "libguile/dynstack.h"
38 #include "libguile/eval.h"
39 #include "libguile/vm.h"
40 #include "libguile/instructions.h"
42 #include "libguile/validate.h"
43 #include "libguile/continuations.h"
47 static scm_t_bits tc16_continuation
;
48 #define SCM_CONTREGSP(x) SCM_TYP16_PREDICATE (tc16_continuation, x)
50 #define SCM_CONTREGS(x) ((scm_t_contregs *) SCM_SMOB_DATA_1 (x))
52 #define SCM_CONTINUATION_LENGTH(x) (SCM_CONTREGS (x)->num_stack_items)
53 #define SCM_SET_CONTINUATION_LENGTH(x, n)\
54 (SCM_CONTREGS (x)->num_stack_items = (n))
55 #define SCM_JMPBUF(x) ((SCM_CONTREGS (x))->jmpbuf)
56 #define SCM_CONTINUATION_ROOT(x) ((SCM_CONTREGS (x))->root)
57 #define SCM_DFRAME(x) ((SCM_CONTREGS (x))->dframe)
61 /* scm_i_make_continuation will return a procedure whose objcode contains an
62 instruction to reinstate the continuation. Here, as in gsubr.c and smob.c, we
63 define the form of that trampoline function.
66 #ifdef WORDS_BIGENDIAN
67 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
68 #define META_HEADER(meta) 0, 0, 0, meta, 0, 0, 0, 0
70 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
71 #define META_HEADER(meta) meta, 0, 0, 0, 0, 0, 0, 0
74 #define OBJCODE_TAG SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0)
76 #if defined (SCM_ALIGNED) && 0
77 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym) \
78 static const type sym[]
79 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym) \
80 static SCM_ALIGNED (alignment) const type sym[]
81 #define SCM_STATIC_OBJCODE(sym) \
82 SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode); \
83 SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = { \
84 { SCM_PACK (OBJCODE_TAG), SCM_PACK (sym##__bytecode) }, \
85 { SCM_BOOL_F, SCM_PACK (0) } \
87 static const SCM sym = SCM_PACK (sym##__cells); \
88 SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
90 #define SCM_STATIC_OBJCODE(sym) \
92 static scm_t_uint8 *sym##_bytecode; \
93 SCM_SNARF_INIT(sym##_bytecode = scm_gc_malloc_pointerless (sizeof(sym##_bytecode__unaligned), "partial continuation stub"); \
94 memcpy (sym##_bytecode, sym##_bytecode__unaligned, sizeof(sym##_bytecode__unaligned));) \
95 SCM_SNARF_INIT(sym = scm_double_cell (OBJCODE_TAG, \
96 (scm_t_bits)sym##_bytecode, \
97 SCM_UNPACK (SCM_BOOL_F), \
99 static const scm_t_uint8 sym##_bytecode__unaligned[]
103 SCM_STATIC_OBJCODE (cont_objcode
) = {
104 /* This code is the same as in gsubr.c, except we use continuation_call
105 instead of subr_call. */
106 OBJCODE_HEADER (8, 19),
107 /* leave args on the stack */
108 /* 0 */ scm_op_object_ref
, 0, /* push scm_t_contregs smob */
109 /* 2 */ scm_op_continuation_call
, /* and longjmp (whee) */
110 /* 3 */ scm_op_nop
, /* pad to 8 bytes */
111 /* 4 */ scm_op_nop
, scm_op_nop
, scm_op_nop
, scm_op_nop
,
114 /* We could put some meta-info to say that this proc is a continuation. Not sure
115 how to do that, though. */
117 /* 0 */ scm_op_make_eol
, /* bindings */
118 /* 1 */ scm_op_make_eol
, /* sources */
119 /* 2 */ scm_op_make_int8
, 0, scm_op_make_int8
, 3, /* arity: from ip 0 to ip 3 */
120 /* 6 */ scm_op_make_int8_0
, /* the arity is 0 required args */
121 /* 7 */ scm_op_make_int8_0
, /* 0 optionals */
122 /* 8 */ scm_op_make_true
, /* and a rest arg */
123 /* 9 */ scm_op_list
, 0, 5, /* make a list of those 5 vals */
124 /* 12 */ scm_op_list
, 0, 1, /* and the arities will be a list of that one list */
125 /* 15 */ scm_op_list
, 0, 3, /* pack bindings, sources, and arities into list */
126 /* 18 */ scm_op_return
/* and return */
131 SCM_STATIC_OBJCODE (call_cc_objcode
) = {
132 /* Before Scheme's call/cc is compiled, eval.c will use this hand-coded
134 OBJCODE_HEADER (8, 17),
135 /* 0 */ scm_op_assert_nargs_ee
, 0, 1, /* assert that nargs==1 */
136 /* 3 */ scm_op_local_ref
, 0, /* push the proc */
137 /* 5 */ scm_op_tail_call_cc
, /* and call/cc */
138 /* 6 */ scm_op_nop
, scm_op_nop
, /* pad to 8 bytes */
142 /* 0 */ scm_op_make_eol
, /* bindings */
143 /* 1 */ scm_op_make_eol
, /* sources */
144 /* 2 */ scm_op_make_int8
, 3, scm_op_make_int8
, 6, /* arity: from ip 0 to ip 6 */
145 /* 6 */ scm_op_make_int8_1
, /* the arity is 0 required args */
146 /* 7 */ scm_op_list
, 0, 3, /* make a list of those 5 vals */
147 /* 10 */ scm_op_list
, 0, 1, /* and the arities will be a list of that one list */
148 /* 13 */ scm_op_list
, 0, 3, /* pack bindings, sources, and arities into list */
149 /* 16 */ scm_op_return
/* and return */
155 make_continuation_trampoline (SCM contregs
)
157 SCM ret
= scm_make_program (cont_objcode
,
158 scm_c_make_vector (1, contregs
),
160 SCM_SET_CELL_WORD_0 (ret
,
161 SCM_CELL_WORD_0 (ret
) | SCM_F_PROGRAM_IS_CONTINUATION
);
172 continuation_print (SCM obj
, SCM port
, scm_print_state
*state SCM_UNUSED
)
174 scm_t_contregs
*continuation
= SCM_CONTREGS (obj
);
176 scm_puts_unlocked ("#<continuation ", port
);
177 scm_intprint (continuation
->num_stack_items
, 10, port
);
178 scm_puts_unlocked (" @ ", port
);
179 scm_uintprint (SCM_SMOB_DATA_1 (obj
), 16, port
);
180 scm_putc_unlocked ('>', port
);
184 /* James Clark came up with this neat one instruction fix for
185 * continuations on the SPARC. It flushes the register windows so
186 * that all the state of the process is contained in the stack.
189 #if defined (sparc) || defined (__sparc__) || defined (__sparc)
190 # define SCM_FLUSH_REGISTER_WINDOWS asm("ta 3")
192 # define SCM_FLUSH_REGISTER_WINDOWS /* empty */
195 /* this may return more than once: the first time with the escape
196 procedure, then subsequently with SCM_UNDEFINED (the vals already having been
197 placed on the VM stack). */
198 #define FUNC_NAME "scm_i_make_continuation"
200 scm_i_make_continuation (int *first
, SCM vm
, SCM vm_cont
)
202 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
204 scm_t_contregs
*continuation
;
208 SCM_FLUSH_REGISTER_WINDOWS
;
209 stack_size
= scm_stack_size (thread
->continuation_base
);
210 continuation
= scm_gc_malloc (sizeof (scm_t_contregs
)
211 + (stack_size
- 1) * sizeof (SCM_STACKITEM
),
213 continuation
->num_stack_items
= stack_size
;
214 continuation
->root
= thread
->continuation_root
;
215 src
= thread
->continuation_base
;
216 #if ! SCM_STACK_GROWS_UP
219 continuation
->offset
= continuation
->stack
- src
;
220 memcpy (continuation
->stack
, src
, sizeof (SCM_STACKITEM
) * stack_size
);
221 continuation
->vm
= vm
;
222 continuation
->vm_cont
= vm_cont
;
224 SCM_NEWSMOB (cont
, tc16_continuation
, continuation
);
226 *first
= !SCM_I_SETJMP (continuation
->jmpbuf
);
230 continuation
->backing_store_size
=
231 (char *) scm_ia64_ar_bsp(&continuation
->jmpbuf
.ctx
)
233 (char *) thread
->register_backing_store_base
;
234 continuation
->backing_store
= NULL
;
235 continuation
->backing_store
=
236 scm_gc_malloc (continuation
->backing_store_size
,
237 "continuation backing store");
238 memcpy (continuation
->backing_store
,
239 (void *) thread
->register_backing_store_base
,
240 continuation
->backing_store_size
);
241 #endif /* __ia64__ */
242 return make_continuation_trampoline (cont
);
245 return SCM_UNDEFINED
;
250 scm_i_call_with_current_continuation (SCM proc
)
252 static SCM call_cc
= SCM_BOOL_F
;
254 if (scm_is_false (call_cc
))
255 call_cc
= scm_make_program (call_cc_objcode
, SCM_BOOL_F
, SCM_BOOL_F
);
257 return scm_call_1 (call_cc
, proc
);
261 scm_i_continuation_to_frame (SCM continuation
)
264 scm_t_contregs
*cont
;
266 contregs
= scm_c_vector_ref (scm_program_objects (continuation
), 0);
267 cont
= SCM_CONTREGS (contregs
);
269 if (scm_is_true (cont
->vm_cont
))
271 struct scm_vm_cont
*data
= SCM_VM_CONT_DATA (cont
->vm_cont
);
272 return scm_c_make_frame (cont
->vm_cont
,
273 data
->fp
+ data
->reloc
,
274 data
->sp
+ data
->reloc
,
283 scm_i_contregs_vm (SCM contregs
)
285 return SCM_CONTREGS (contregs
)->vm
;
289 scm_i_contregs_vm_cont (SCM contregs
)
291 return SCM_CONTREGS (contregs
)->vm_cont
;
298 /* Invoking a continuation proceeds as follows:
300 * - the stack is made large enough for the called continuation
301 * - the old windchain is unwound down to the branching point
302 * - the continuation stack is copied into place
303 * - the windchain is rewound up to the continuation's context
304 * - the continuation is invoked via longjmp (or setcontext)
306 * This order is important so that unwind and rewind handlers are run
307 * with their correct stack.
310 static void scm_dynthrow (SCM
);
312 /* Grow the stack by a fixed amount to provide space to copy in the
313 * continuation. Possibly this function has to be called several times
314 * recursively before enough space is available. Make sure the compiler does
315 * not optimize the growth array away by storing it's address into a global
319 static scm_t_bits scm_i_dummy
;
322 grow_stack (SCM cont
)
324 scm_t_bits growth
[100];
326 scm_i_dummy
= (scm_t_bits
) growth
;
331 /* Copy the continuation stack into the current stack. Calling functions from
332 * within this function is safe, since only stack frames below this function's
333 * own frame are overwritten. Thus, memcpy can be used for best performance.
337 copy_stack_and_call (scm_t_contregs
*continuation
,
340 scm_t_dynstack
*dynstack
;
342 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
344 dynstack
= SCM_VM_CONT_DATA (continuation
->vm_cont
)->dynstack
;
346 joint
= scm_dynstack_unwind_fork (&thread
->dynstack
, dynstack
);
348 memcpy (dst
, continuation
->stack
,
349 sizeof (SCM_STACKITEM
) * continuation
->num_stack_items
);
351 thread
->pending_rbs_continuation
= continuation
;
354 scm_dynstack_wind (&thread
->dynstack
, joint
);
356 SCM_I_LONGJMP (continuation
->jmpbuf
, 1);
361 scm_ia64_longjmp (scm_i_jmp_buf
*JB
, int VAL
)
363 scm_i_thread
*t
= SCM_I_CURRENT_THREAD
;
365 if (t
->pending_rbs_continuation
)
367 memcpy (t
->register_backing_store_base
,
368 t
->pending_rbs_continuation
->backing_store
,
369 t
->pending_rbs_continuation
->backing_store_size
);
370 t
->pending_rbs_continuation
= NULL
;
372 setcontext (&JB
->ctx
);
376 /* Call grow_stack until the stack space is large enough, then, as the current
377 * stack frame might get overwritten, let copy_stack_and_call perform the
378 * actual copying and continuation calling.
381 scm_dynthrow (SCM cont
)
383 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
384 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
385 SCM_STACKITEM
*dst
= thread
->continuation_base
;
386 SCM_STACKITEM stack_top_element
;
388 if (thread
->critical_section_level
)
390 fprintf (stderr
, "continuation invoked from within critical section.\n");
394 #if SCM_STACK_GROWS_UP
395 if (dst
+ continuation
->num_stack_items
>= &stack_top_element
)
398 dst
-= continuation
->num_stack_items
;
399 if (dst
<= &stack_top_element
)
401 #endif /* def SCM_STACK_GROWS_UP */
403 SCM_FLUSH_REGISTER_WINDOWS
;
404 copy_stack_and_call (continuation
, dst
);
409 scm_i_check_continuation (SCM cont
)
411 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
412 scm_t_contregs
*continuation
= SCM_CONTREGS (cont
);
414 if (!scm_is_eq (continuation
->root
, thread
->continuation_root
))
416 ("%continuation-call",
417 "invoking continuation would cross continuation barrier: ~A",
422 scm_i_reinstate_continuation (SCM cont
)
428 scm_i_with_continuation_barrier (scm_t_catch_body body
,
430 scm_t_catch_handler handler
,
432 scm_t_catch_handler pre_unwind_handler
,
433 void *pre_unwind_handler_data
)
435 SCM_STACKITEM stack_item
;
436 scm_i_thread
*thread
= SCM_I_CURRENT_THREAD
;
438 SCM_STACKITEM
*old_contbase
;
441 /* Establish a fresh continuation root.
443 old_controot
= thread
->continuation_root
;
444 old_contbase
= thread
->continuation_base
;
445 thread
->continuation_root
= scm_cons (thread
->handle
, old_controot
);
446 thread
->continuation_base
= &stack_item
;
448 /* Call FUNC inside a catch all. This is now guaranteed to return
449 directly and exactly once.
451 result
= scm_c_catch (SCM_BOOL_T
,
453 handler
, handler_data
,
454 pre_unwind_handler
, pre_unwind_handler_data
);
456 /* Return to old continuation root.
458 thread
->continuation_base
= old_contbase
;
459 thread
->continuation_root
= old_controot
;
467 should_print_backtrace (SCM tag
, SCM stack
)
469 return SCM_BACKTRACE_P
470 && scm_is_true (stack
)
472 /* It's generally not useful to print backtraces for errors reading
473 or expanding code in these fallback catch statements. */
474 && !scm_is_eq (tag
, scm_from_latin1_symbol ("read-error"))
475 && !scm_is_eq (tag
, scm_from_latin1_symbol ("syntax-error"));
479 print_exception_and_backtrace (SCM port
, SCM tag
, SCM args
)
483 /* We get here via a throw to a catch-all. In that case there is the
484 throw frame active, and this catch closure, so narrow by two
486 stack
= scm_make_stack (SCM_BOOL_T
, scm_list_1 (scm_from_int (2)));
487 frame
= scm_is_true (stack
) ? scm_stack_ref (stack
, SCM_INUM0
) : SCM_BOOL_F
;
489 if (should_print_backtrace (tag
, stack
))
491 scm_puts_unlocked ("Backtrace:\n", port
);
492 scm_display_backtrace_with_highlights (stack
, port
,
493 SCM_BOOL_F
, SCM_BOOL_F
,
498 scm_print_exception (port
, frame
, tag
, args
);
504 void *(*func
) (void *);
512 struct c_data
*data
= (struct c_data
*)d
;
513 data
->result
= data
->func (data
->data
);
514 return SCM_UNSPECIFIED
;
518 c_handler (void *d
, SCM tag
, SCM args
)
522 /* If TAG is `quit', exit() the process. */
523 if (scm_is_eq (tag
, scm_from_latin1_symbol ("quit")))
524 exit (scm_exit_status (args
));
526 data
= (struct c_data
*)d
;
528 return SCM_UNSPECIFIED
;
532 pre_unwind_handler (void *error_port
, SCM tag
, SCM args
)
534 /* Print the exception unless TAG is `quit'. */
535 if (!scm_is_eq (tag
, scm_from_latin1_symbol ("quit")))
536 print_exception_and_backtrace (SCM_PACK_POINTER (error_port
), tag
, args
);
538 return SCM_UNSPECIFIED
;
542 scm_c_with_continuation_barrier (void *(*func
) (void *), void *data
)
544 struct c_data c_data
;
547 scm_i_with_continuation_barrier (c_body
, &c_data
,
550 SCM_UNPACK_POINTER (scm_current_error_port ()));
551 return c_data
.result
;
561 struct scm_data
*data
= (struct scm_data
*)d
;
562 return scm_call_0 (data
->proc
);
566 scm_handler (void *d
, SCM tag
, SCM args
)
568 /* Print a message. Note that if TAG is `quit', this will exit() the
570 scm_handle_by_message_noexit (NULL
, tag
, args
);
575 SCM_DEFINE (scm_with_continuation_barrier
, "with-continuation-barrier", 1,0,0,
577 "Call @var{proc} and return its result. Do not allow the invocation of\n"
578 "continuations that would leave or enter the dynamic extent of the call\n"
579 "to @code{with-continuation-barrier}. Such an attempt causes an error\n"
582 "Throws (such as errors) that are not caught from within @var{proc} are\n"
583 "caught by @code{with-continuation-barrier}. In that case, a short\n"
584 "message is printed to the current error port and @code{#f} is returned.\n"
586 "Thus, @code{with-continuation-barrier} returns exactly once.\n")
587 #define FUNC_NAME s_scm_with_continuation_barrier
589 struct scm_data scm_data
;
590 scm_data
.proc
= proc
;
591 return scm_i_with_continuation_barrier (scm_body
, &scm_data
,
592 scm_handler
, &scm_data
,
594 SCM_UNPACK_POINTER (scm_current_error_port ()));
599 scm_init_continuations ()
601 tc16_continuation
= scm_make_smob_type ("continuation", 0);
602 scm_set_smob_print (tc16_continuation
, continuation_print
);
603 #include "libguile/continuations.x"