/* Copyright (C) 1995,1996,1998,2000,2001,2004, 2006, 2008 Free Software Foundation, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public License * as published by the Free Software Foundation; either version 3 of * the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301 USA */ #ifdef HAVE_CONFIG_H # include #endif #include "libguile/_scm.h" #include #include #include "libguile/async.h" #include "libguile/debug.h" #include "libguile/root.h" #include "libguile/stackchk.h" #include "libguile/smob.h" #include "libguile/ports.h" #include "libguile/dynwind.h" #include "libguile/values.h" #include "libguile/eval.h" #include "libguile/vm.h" #include "libguile/validate.h" #include "libguile/continuations.h" /* {Continuations} */ scm_t_bits scm_tc16_continuation; static int continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED) { scm_t_contregs *continuation = SCM_CONTREGS (obj); scm_puts ("#num_stack_items, 10, port); scm_puts (" @ ", port); scm_uintprint (SCM_CELL_WORD_1 (obj), 16, port); scm_putc ('>', port); return 1; } /* this may return more than once: the first time with the escape procedure, then subsequently with the value to be passed to the continuation. */ #define FUNC_NAME "scm_make_continuation" SCM scm_make_continuation (int *first) { scm_i_thread *thread = SCM_I_CURRENT_THREAD; SCM cont; scm_t_contregs *continuation; long stack_size; SCM_STACKITEM * src; SCM_FLUSH_REGISTER_WINDOWS; stack_size = scm_stack_size (thread->continuation_base); continuation = scm_gc_malloc (sizeof (scm_t_contregs) + (stack_size - 1) * sizeof (SCM_STACKITEM), "continuation"); continuation->num_stack_items = stack_size; continuation->dynenv = scm_i_dynwinds (); continuation->throw_value = SCM_EOL; continuation->root = thread->continuation_root; continuation->dframe = scm_i_last_debug_frame (); src = thread->continuation_base; #if ! SCM_STACK_GROWS_UP src -= stack_size; #endif continuation->offset = continuation->stack - src; memcpy (continuation->stack, src, sizeof (SCM_STACKITEM) * stack_size); continuation->vm_conts = scm_vm_capture_continuations (); SCM_NEWSMOB (cont, scm_tc16_continuation, continuation); *first = !SCM_I_SETJMP (continuation->jmpbuf); if (*first) { #ifdef __ia64__ continuation->backing_store_size = (char *) scm_ia64_ar_bsp(&continuation->jmpbuf.ctx) - (char *) thread->register_backing_store_base; continuation->backing_store = NULL; continuation->backing_store = scm_gc_malloc (continuation->backing_store_size, "continuation backing store"); memcpy (continuation->backing_store, (void *) thread->register_backing_store_base, continuation->backing_store_size); #endif /* __ia64__ */ return cont; } else { SCM ret = continuation->throw_value; continuation->throw_value = SCM_BOOL_F; return ret; } } #undef FUNC_NAME /* Invoking a continuation proceeds as follows: * * - the stack is made large enough for the called continuation * - the old windchain is unwound down to the branching point * - the continuation stack is copied into place * - the windchain is rewound up to the continuation's context * - the continuation is invoked via longjmp (or setcontext) * * This order is important so that unwind and rewind handlers are run * with their correct stack. */ static void scm_dynthrow (SCM, SCM); /* Grow the stack by a fixed amount to provide space to copy in the * continuation. Possibly this function has to be called several times * recursively before enough space is available. Make sure the compiler does * not optimize the growth array away by storing it's address into a global * variable. */ scm_t_bits scm_i_dummy; static void grow_stack (SCM cont, SCM val) { scm_t_bits growth[100]; scm_i_dummy = (scm_t_bits) growth; scm_dynthrow (cont, val); } /* Copy the continuation stack into the current stack. Calling functions from * within this function is safe, since only stack frames below this function's * own frame are overwritten. Thus, memcpy can be used for best performance. */ typedef struct { scm_t_contregs *continuation; SCM_STACKITEM *dst; } copy_stack_data; static void copy_stack (void *data) { copy_stack_data *d = (copy_stack_data *)data; memcpy (d->dst, d->continuation->stack, sizeof (SCM_STACKITEM) * d->continuation->num_stack_items); scm_vm_reinstate_continuations (d->continuation->vm_conts); #ifdef __ia64__ SCM_I_CURRENT_THREAD->pending_rbs_continuation = d->continuation; #endif } static void copy_stack_and_call (scm_t_contregs *continuation, SCM val, SCM_STACKITEM * dst) { long delta; copy_stack_data data; delta = scm_ilength (scm_i_dynwinds ()) - scm_ilength (continuation->dynenv); data.continuation = continuation; data.dst = dst; scm_i_dowinds (continuation->dynenv, delta, copy_stack, &data); scm_i_set_last_debug_frame (continuation->dframe); continuation->throw_value = val; SCM_I_LONGJMP (continuation->jmpbuf, 1); } #ifdef __ia64__ void scm_ia64_longjmp (scm_i_jmp_buf *JB, int VAL) { scm_i_thread *t = SCM_I_CURRENT_THREAD; if (t->pending_rbs_continuation) { memcpy (t->register_backing_store_base, t->pending_rbs_continuation->backing_store, t->pending_rbs_continuation->backing_store_size); t->pending_rbs_continuation = NULL; } setcontext (&JB->ctx); } #endif /* Call grow_stack until the stack space is large enough, then, as the current * stack frame might get overwritten, let copy_stack_and_call perform the * actual copying and continuation calling. */ static void scm_dynthrow (SCM cont, SCM val) { scm_i_thread *thread = SCM_I_CURRENT_THREAD; scm_t_contregs *continuation = SCM_CONTREGS (cont); SCM_STACKITEM *dst = thread->continuation_base; SCM_STACKITEM stack_top_element; if (thread->critical_section_level) { fprintf (stderr, "continuation invoked from within critical section.\n"); abort (); } #if SCM_STACK_GROWS_UP if (dst + continuation->num_stack_items >= &stack_top_element) grow_stack (cont, val); #else dst -= continuation->num_stack_items; if (dst <= &stack_top_element) grow_stack (cont, val); #endif /* def SCM_STACK_GROWS_UP */ SCM_FLUSH_REGISTER_WINDOWS; copy_stack_and_call (continuation, val, dst); } static SCM continuation_apply (SCM cont, SCM args) #define FUNC_NAME "continuation_apply" { scm_i_thread *thread = SCM_I_CURRENT_THREAD; scm_t_contregs *continuation = SCM_CONTREGS (cont); if (continuation->root != thread->continuation_root) { SCM_MISC_ERROR ("invoking continuation would cross continuation barrier: ~A", scm_list_1 (cont)); } scm_dynthrow (cont, scm_values (args)); return SCM_UNSPECIFIED; /* not reached */ } #undef FUNC_NAME SCM scm_i_with_continuation_barrier (scm_t_catch_body body, void *body_data, scm_t_catch_handler handler, void *handler_data, scm_t_catch_handler pre_unwind_handler, void *pre_unwind_handler_data) { SCM_STACKITEM stack_item; scm_i_thread *thread = SCM_I_CURRENT_THREAD; SCM old_controot; SCM_STACKITEM *old_contbase; scm_t_debug_frame *old_lastframe; SCM result; /* Establish a fresh continuation root. */ old_controot = thread->continuation_root; old_contbase = thread->continuation_base; old_lastframe = thread->last_debug_frame; thread->continuation_root = scm_cons (thread->handle, old_controot); thread->continuation_base = &stack_item; thread->last_debug_frame = NULL; /* Call FUNC inside a catch all. This is now guaranteed to return directly and exactly once. */ result = scm_c_catch (SCM_BOOL_T, body, body_data, handler, handler_data, pre_unwind_handler, pre_unwind_handler_data); /* Return to old continuation root. */ thread->last_debug_frame = old_lastframe; thread->continuation_base = old_contbase; thread->continuation_root = old_controot; return result; } struct c_data { void *(*func) (void *); void *data; void *result; }; static SCM c_body (void *d) { struct c_data *data = (struct c_data *)d; data->result = data->func (data->data); return SCM_UNSPECIFIED; } static SCM c_handler (void *d, SCM tag, SCM args) { struct c_data *data = (struct c_data *)d; data->result = NULL; return SCM_UNSPECIFIED; } void * scm_c_with_continuation_barrier (void *(*func) (void *), void *data) { struct c_data c_data; c_data.func = func; c_data.data = data; scm_i_with_continuation_barrier (c_body, &c_data, c_handler, &c_data, scm_handle_by_message_noexit, NULL); return c_data.result; } struct scm_data { SCM proc; }; static SCM scm_body (void *d) { struct scm_data *data = (struct scm_data *)d; return scm_call_0 (data->proc); } static SCM scm_handler (void *d, SCM tag, SCM args) { return SCM_BOOL_F; } SCM_DEFINE (scm_with_continuation_barrier, "with-continuation-barrier", 1,0,0, (SCM proc), "Call @var{proc} and return its result. Do not allow the invocation of\n" "continuations that would leave or enter the dynamic extent of the call\n" "to @code{with-continuation-barrier}. Such an attempt causes an error\n" "to be signaled.\n" "\n" "Throws (such as errors) that are not caught from within @var{proc} are\n" "caught by @code{with-continuation-barrier}. In that case, a short\n" "message is printed to the current error port and @code{#f} is returned.\n" "\n" "Thus, @code{with-continuation-barrier} returns exactly once.\n") #define FUNC_NAME s_scm_with_continuation_barrier { struct scm_data scm_data; scm_data.proc = proc; return scm_i_with_continuation_barrier (scm_body, &scm_data, scm_handler, &scm_data, scm_handle_by_message_noexit, NULL); } #undef FUNC_NAME void scm_init_continuations () { scm_tc16_continuation = scm_make_smob_type ("continuation", 0); scm_set_smob_print (scm_tc16_continuation, continuation_print); scm_set_smob_apply (scm_tc16_continuation, continuation_apply, 0, 0, 1); #include "libguile/continuations.x" } /* Local Variables: c-file-style: "gnu" End: */