/* Copyright (C) 1995,1996,1998,2000,2001,2004, 2006, 2008, 2009, 2010, 2011, 2012, 2013, 2014 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 #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/dynstack.h" #include "libguile/eval.h" #include "libguile/vm.h" #include "libguile/instructions.h" #include "libguile/validate.h" #include "libguile/continuations.h" static scm_t_bits tc16_continuation; #define SCM_CONTREGSP(x) SCM_TYP16_PREDICATE (tc16_continuation, x) #define SCM_CONTREGS(x) ((scm_t_contregs *) SCM_SMOB_DATA_1 (x)) #define SCM_CONTINUATION_LENGTH(x) (SCM_CONTREGS (x)->num_stack_items) #define SCM_SET_CONTINUATION_LENGTH(x, n)\ (SCM_CONTREGS (x)->num_stack_items = (n)) #define SCM_JMPBUF(x) ((SCM_CONTREGS (x))->jmpbuf) #define SCM_CONTINUATION_ROOT(x) ((SCM_CONTREGS (x))->root) #define SCM_DFRAME(x) ((SCM_CONTREGS (x))->dframe) /* scm_i_make_continuation will return a procedure whose code will reinstate the continuation. Here, as in gsubr.c, we define the form of that trampoline function. */ static const scm_t_uint32 continuation_stub_code[] = { SCM_PACK_OP_24 (continuation_call, 0) }; static SCM make_continuation_trampoline (SCM contregs) { SCM ret; scm_t_bits nfree = 1; scm_t_bits flags = SCM_F_PROGRAM_IS_CONTINUATION; ret = scm_words (scm_tc7_program | (nfree << 16) | flags, nfree + 2); SCM_SET_CELL_WORD_1 (ret, continuation_stub_code); SCM_PROGRAM_FREE_VARIABLE_SET (ret, 0, contregs); return ret; } /* {Continuations} */ static int continuation_print (SCM obj, SCM port, scm_print_state *state SCM_UNUSED) { scm_t_contregs *continuation = SCM_CONTREGS (obj); scm_puts_unlocked ("#num_stack_items, 10, port); scm_puts_unlocked (" @ ", port); scm_uintprint (SCM_SMOB_DATA_1 (obj), 16, port); scm_putc_unlocked ('>', port); return 1; } /* James Clark came up with this neat one instruction fix for * continuations on the SPARC. It flushes the register windows so * that all the state of the process is contained in the stack. */ #if defined (sparc) || defined (__sparc__) || defined (__sparc) # define SCM_FLUSH_REGISTER_WINDOWS asm("ta 3") #else # define SCM_FLUSH_REGISTER_WINDOWS /* empty */ #endif /* this may return more than once: the first time with the escape procedure, then subsequently with SCM_UNDEFINED (the vals already having been placed on the VM stack). */ #define FUNC_NAME "scm_i_make_continuation" SCM scm_i_make_continuation (int *first, struct scm_vm *vp, SCM vm_cont) { 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->root = thread->continuation_root; 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->vp = vp; continuation->vm_cont = vm_cont; SCM_NEWSMOB (cont, 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 make_continuation_trampoline (cont); } else { scm_gc_after_nonlocal_exit (); return SCM_UNDEFINED; } } #undef FUNC_NAME int scm_i_continuation_to_frame (SCM continuation, struct scm_frame *frame) { SCM contregs; scm_t_contregs *cont; contregs = SCM_PROGRAM_FREE_VARIABLE_REF (continuation, 0); cont = SCM_CONTREGS (contregs); if (scm_is_true (cont->vm_cont)) { struct scm_vm_cont *data = SCM_VM_CONT_DATA (cont->vm_cont); frame->stack_holder = data; frame->fp_offset = (data->fp + data->reloc) - data->stack_base; frame->sp_offset = (data->sp + data->reloc) - data->stack_base; frame->ip = data->ra; return 1; } else return 0; } struct scm_vm * scm_i_contregs_vp (SCM contregs) { return SCM_CONTREGS (contregs)->vp; } SCM scm_i_contregs_vm_cont (SCM contregs) { return SCM_CONTREGS (contregs)->vm_cont; } /* {Apply} */ /* 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); /* 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. */ static scm_t_bits scm_i_dummy; static void grow_stack (SCM cont) { scm_t_bits growth[100]; scm_i_dummy = (scm_t_bits) growth; scm_dynthrow (cont); } /* 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. */ static void copy_stack_and_call (scm_t_contregs *continuation, SCM_STACKITEM * dst) { scm_t_dynstack *dynstack; scm_t_bits *joint; scm_i_thread *thread = SCM_I_CURRENT_THREAD; dynstack = SCM_VM_CONT_DATA (continuation->vm_cont)->dynstack; joint = scm_dynstack_unwind_fork (&thread->dynstack, dynstack); memcpy (dst, continuation->stack, sizeof (SCM_STACKITEM) * continuation->num_stack_items); #ifdef __ia64__ thread->pending_rbs_continuation = continuation; #endif scm_dynstack_wind (&thread->dynstack, joint); 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_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); #else dst -= continuation->num_stack_items; if (dst <= &stack_top_element) grow_stack (cont); #endif /* def SCM_STACK_GROWS_UP */ SCM_FLUSH_REGISTER_WINDOWS; copy_stack_and_call (continuation, dst); } void scm_i_check_continuation (SCM cont) { scm_i_thread *thread = SCM_I_CURRENT_THREAD; scm_t_contregs *continuation = SCM_CONTREGS (cont); if (!scm_is_eq (continuation->root, thread->continuation_root)) scm_misc_error ("%continuation-call", "invoking continuation would cross continuation barrier: ~A", scm_list_1 (cont)); } void scm_i_reinstate_continuation (SCM cont) { scm_dynthrow (cont); } 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 result; /* Establish a fresh continuation root. */ old_controot = thread->continuation_root; old_contbase = thread->continuation_base; thread->continuation_root = scm_cons (thread->handle, old_controot); thread->continuation_base = &stack_item; /* 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->continuation_base = old_contbase; thread->continuation_root = old_controot; return result; } static int should_print_backtrace (SCM tag, SCM stack) { return SCM_BACKTRACE_P && scm_is_true (stack) && scm_initialized_p /* It's generally not useful to print backtraces for errors reading or expanding code in these fallback catch statements. */ && !scm_is_eq (tag, scm_from_latin1_symbol ("read-error")) && !scm_is_eq (tag, scm_from_latin1_symbol ("syntax-error")); } static void print_exception_and_backtrace (SCM port, SCM tag, SCM args) { SCM stack, frame; /* We get here via a throw to a catch-all. In that case there is the throw frame active, and this catch closure, so narrow by two frames. */ stack = scm_make_stack (SCM_BOOL_T, scm_list_1 (scm_from_int (2))); frame = scm_is_true (stack) ? scm_stack_ref (stack, SCM_INUM0) : SCM_BOOL_F; if (should_print_backtrace (tag, stack)) { scm_puts_unlocked ("Backtrace:\n", port); scm_display_backtrace_with_highlights (stack, port, SCM_BOOL_F, SCM_BOOL_F, SCM_EOL); scm_newline (port); } scm_print_exception (port, frame, tag, args); } 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; /* If TAG is `quit', exit() the process. */ if (scm_is_eq (tag, scm_from_latin1_symbol ("quit"))) exit (scm_exit_status (args)); data = (struct c_data *)d; data->result = NULL; return SCM_UNSPECIFIED; } static SCM pre_unwind_handler (void *error_port, SCM tag, SCM args) { /* Print the exception unless TAG is `quit'. */ if (!scm_is_eq (tag, scm_from_latin1_symbol ("quit"))) print_exception_and_backtrace (SCM_PACK_POINTER (error_port), tag, args); 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, pre_unwind_handler, SCM_UNPACK_POINTER (scm_current_error_port ())); 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) { /* Print a message. Note that if TAG is `quit', this will exit() the process. */ scm_handle_by_message_noexit (NULL, tag, 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, pre_unwind_handler, SCM_UNPACK_POINTER (scm_current_error_port ())); } #undef FUNC_NAME void scm_init_continuations () { tc16_continuation = scm_make_smob_type ("continuation", 0); scm_set_smob_print (tc16_continuation, continuation_print); #include "libguile/continuations.x" } /* Local Variables: c-file-style: "gnu" End: */