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Diffstat (limited to 'libguile/continuations.c')
-rw-r--r-- | libguile/continuations.c | 521 |
1 files changed, 521 insertions, 0 deletions
diff --git a/libguile/continuations.c b/libguile/continuations.c new file mode 100644 index 000000000..3f86c6bd4 --- /dev/null +++ b/libguile/continuations.c @@ -0,0 +1,521 @@ +/* Copyright 1995-1996,1998,2000-2001,2004,2006,2008-2014,2017-2018 + Free Software Foundation, Inc. + + This file is part of Guile. + + Guile 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. + + Guile 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 Guile. If not, see + <https://www.gnu.org/licenses/>. */ + + + + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif + +#include <assert.h> +#include <string.h> +#include <stdio.h> + +#if SCM_HAVE_AUXILIARY_STACK +#include <ucontext.h> +#endif + +#include "async.h" +#include "backtrace.h" +#include "boolean.h" +#include "debug.h" +#include "dynstack.h" +#include "eval.h" +#include "gsubr.h" +#include "init.h" +#include "instructions.h" +#include "jit.h" +#include "list.h" +#include "numbers.h" +#include "pairs.h" +#include "ports.h" +#include "smob.h" +#include "stackchk.h" +#include "stacks.h" +#include "symbols.h" +#include "vm.h" + +#include "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. + */ + +struct goto_continuation_code +{ + struct scm_jit_function_data data; + uint32_t code[3]; +}; + +struct goto_continuation_code goto_continuation_code = { + { + /* mcode = */ 0, + /* counter = */ 0, + /* start = */ sizeof (struct scm_jit_function_data), + /* end = */ sizeof (struct scm_jit_function_data) + 12 + }, + { + SCM_PACK_OP_24 (instrument_entry, 0), + ((uint32_t) -(sizeof (struct scm_jit_function_data) / 4)), + 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, goto_continuation_code.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 ("#<continuation ", port); + scm_intprint (continuation->num_stack_items, 10, port); + scm_puts (" @ ", port); + scm_uintprint (SCM_SMOB_DATA_1 (obj), 16, port); + scm_putc ('>', 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 + +static void +capture_auxiliary_stack (scm_thread *thread, scm_t_contregs *continuation) +{ +#if SCM_HAVE_AUXILIARY_STACK +# if !(defined __ia64 or defined __ia64__) +# error missing auxiliary stack implementation for architecture +# endif + char *top; + ucontext_t ctx; + + if (getcontext (&ctx) != 0) + abort (); + +#if defined __hpux + __uc_get_ar_bsp (ctx, (uint64_t *) &top); +#elif defined linux + top = (char *) ctx->uc_mcontext.sc_ar_bsp; +#elif defined __FreeBSD__ + top = (char *)(ctx->uc_mcontext.mc_special.bspstore + + ctx->uc_mcontext.mc_special.ndirty); +#else +#error missing auxiliary stack implementation for ia64 on this OS +#endif + + continuation->auxiliary_stack_size = + top - (char *) thread->auxiliary_stack_base; + continuation->auxiliary_stack = + scm_gc_malloc (continuation->auxiliary_stack_size, + "continuation auxiliary stack"); + memcpy (continuation->auxiliary_stack, thread->auxiliary_stack_base, + continuation->auxiliary_stack_size); +#endif /* SCM_HAVE_AUXILIARY_STACK */ +} + +static void +restore_auxiliary_stack (scm_thread *thread, scm_t_contregs *continuation) +{ +#if SCM_HAVE_AUXILIARY_STACK + memcpy (thread->auxiliary_stack_base, continuation->auxiliary_stack, + continuation->auxiliary_stack_size); +#endif +} + +SCM +scm_i_make_continuation (scm_thread *thread, SCM vm_cont) +{ + 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); + memcpy (continuation->jmpbuf, thread->vm.registers, sizeof (jmp_buf)); + continuation->vm_cont = vm_cont; + capture_auxiliary_stack (thread, continuation); + + SCM_NEWSMOB (cont, tc16_continuation, continuation); + + return make_continuation_trampoline (cont); +} + +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_offset; + frame->sp_offset = data->stack_size; + frame->ip = data->vra; + + return 1; + } + else + return 0; +} + +scm_t_contregs * +scm_i_contregs (SCM contregs) +{ + if (!SCM_CONTREGSP (contregs)) + abort (); + + return SCM_CONTREGS (contregs); +} + + +/* {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, uint8_t *); + +/* 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, uint8_t *mra) +{ + scm_t_bits growth[100]; + + scm_i_dummy = (scm_t_bits) growth; + scm_dynthrow (cont, mra); +} + + +/* 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, uint8_t *mra) +{ + scm_t_dynstack *dynstack; + scm_t_bits *joint; + scm_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); + restore_auxiliary_stack (thread, continuation); + + scm_dynstack_wind (&thread->dynstack, joint); + + thread->vm.mra_after_abort = mra; + longjmp (continuation->jmpbuf, 1); +} + +/* 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, uint8_t *mra) +{ + scm_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 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, mra); +#endif /* def SCM_STACK_GROWS_UP */ + + SCM_FLUSH_REGISTER_WINDOWS; + copy_stack_and_call (continuation, dst, mra); +} + +void +scm_i_reinstate_continuation (SCM cont, uint8_t *mra) +{ + scm_dynthrow (cont, mra); + abort (); /* Unreachable. */ +} + +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_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 ("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 "continuations.x" +} |