libguile/root.c

   1 /*      Copyright (C) 1995,1996,1997,1998 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program 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
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41 \f
  42
  43 #include <stdio.h>
  44 #include "_scm.h"
  45 #include "stackchk.h"
  46 #include "dynwind.h"
  47 #include "eval.h"
  48 #include "genio.h"
  49 #include "smob.h"
  50 #include "pairs.h"
  51 #include "throw.h"
  52 #include "fluids.h"
  53
  54 #include "root.h"
  55 \f
  56
  57 /* Define this if you want to try out the stack allocation of cwdr's
  58    jumpbuf.  It works for me but I'm still worried that the dynwinds
  59    might be able to make a mess. */
  60
  61 #undef USE_STACKJMPBUF
  62
  63 SCM scm_sys_protects[SCM_NUM_PROTECTS];
  64
  65 long scm_tc16_root;
  66
  67 #ifndef USE_THREADS
  68 struct scm_root_state *scm_root;
  69 #endif
  70
  71 \f
  72
  73 static SCM mark_root SCM_P ((SCM));
  74
  75 static SCM
  76 mark_root (root)
  77      SCM root;
  78 {
  79   scm_root_state *s = SCM_ROOT_STATE (root);
  80
  81   scm_gc_mark (s->rootcont);
  82   scm_gc_mark (s->dynwinds);
  83   scm_gc_mark (s->continuation_stack);
  84   scm_gc_mark (s->continuation_stack_ptr);
  85   scm_gc_mark (s->progargs);
  86   scm_gc_mark (s->exitval);
  87   scm_gc_mark (s->cur_inp);
  88   scm_gc_mark (s->cur_outp);
  89   scm_gc_mark (s->cur_errp);
  90   scm_gc_mark (s->def_inp);
  91   scm_gc_mark (s->def_outp);
  92   scm_gc_mark (s->def_errp);
  93   /* No need to gc mark def_loadp */
  94   scm_gc_mark (s->fluids);
  95   scm_gc_mark (s->top_level_lookup_closure_var);
  96   scm_gc_mark (s->system_transformer);
  97   return SCM_ROOT_STATE (root) -> parent;
  98 }
  99
 100
 101 static int print_root SCM_P ((SCM exp, SCM port, scm_print_state *pstate));
 102
 103 static int
 104 print_root (exp, port, pstate)
 105      SCM exp;
 106      SCM port;
 107      scm_print_state *pstate;
 108 {
 109   scm_puts ("#<root ", port);
 110   scm_intprint(SCM_SEQ (SCM_ROOT_STATE (exp) -> rootcont), 16, port);
 111   scm_putc('>', port);
 112   return 1;
 113 }
 114
 115
 116 \f
 117
 118 SCM
 119 scm_make_root (parent)
 120      SCM parent;
 121 {
 122   SCM root;
 123   scm_root_state *root_state;
 124
 125   root_state = (scm_root_state *) scm_must_malloc (sizeof (scm_root_state),
 126                                                    "scm_make_root");
 127   if (SCM_NIMP (parent) && SCM_ROOTP (parent))
 128     {
 129       memcpy (root_state, SCM_ROOT_STATE (parent), sizeof (scm_root_state));
 130       scm_copy_fluids (root_state);
 131       root_state->parent = parent;
 132     }
 133   else
 134     {
 135       root_state->parent = SCM_BOOL_F;
 136     }
 137   SCM_REDEFER_INTS;
 138   SCM_NEWSMOB (root, scm_tc16_root, root_state);
 139   root_state->handle = root;
 140   SCM_REALLOW_INTS;
 141   return root;
 142 }
 143
 144 /* {call-with-dynamic-root}
 145  *
 146  * Suspending the current thread to evaluate a thunk on the
 147  * same C stack but under a new root.
 148  *
 149  * Calls to call-with-dynamic-root return exactly once (unless
 150  * the process is somehow exitted).  */
 151
 152 /* Some questions about cwdr:
 153
 154    Couldn't the body just be a closure?  Do we really need to pass
 155    args through to it?
 156
 157    The semantics are a lot like catch's; in fact, we call
 158    scm_internal_catch to take care of that part of things.  Wouldn't
 159    it be cleaner to say that uncaught throws just disappear into the
 160    ether (or print a message to stderr), and let the caller use catch
 161    themselves if they want to?
 162
 163    -JimB */
 164
 165 #if 0
 166 SCM scm_exitval;                /* INUM with return value */
 167 #endif
 168 static int n_dynamic_roots = 0;
 169
 170
 171 /* cwdr fills out both of these structures, and then passes a pointer
 172    to them through scm_internal_catch to the cwdr_body and
 173    cwdr_handler functions, to tell them how to behave and to get
 174    information back from them.
 175
 176    A cwdr is a lot like a catch, except there is no tag (all
 177    exceptions are caught), and the body procedure takes the arguments
 178    passed to cwdr as A1 and ARGS.  The handler is also special since
 179    it is not directly run from scm_internal_catch.  It is executed
 180    outside the new dynamic root. */
 181
 182 struct cwdr_body_data {
 183   /* Arguments to pass to the cwdr body function.  */
 184   SCM a1, args;
 185
 186   /* Scheme procedure to use as body of cwdr.  */
 187   SCM body_proc;
 188 };
 189
 190 struct cwdr_handler_data {
 191   /* Do we need to run the handler? */
 192   int run_handler;
 193
 194   /* The tag and args to pass it. */
 195   SCM tag, args;
 196 };
 197
 198
 199 /* Invoke the body of a cwdr, assuming that the throw handler has
 200    already been set up.  DATA points to a struct set up by cwdr that
 201    says what proc to call, and what args to apply it to.
 202
 203    With a little thought, we could replace this with scm_body_thunk,
 204    but I don't want to mess with that at the moment.  */
 205 static SCM
 206 cwdr_body (void *data)
 207 {
 208   struct cwdr_body_data *c = (struct cwdr_body_data *) data;
 209
 210   return scm_apply (c->body_proc, c->a1, c->args);
 211 }
 212
 213 /* Record the fact that the body of the cwdr has thrown.  Record
 214    enough information to invoke the handler later when the dynamic
 215    root has been deestablished.  */
 216
 217 static SCM
 218 cwdr_handler (void *data, SCM tag, SCM args)
 219 {
 220   struct cwdr_handler_data *c = (struct cwdr_handler_data *) data;
 221
 222   c->run_handler = 1;
 223   c->tag = tag;
 224   c->args = args;
 225   return SCM_UNSPECIFIED;
 226 }
 227
 228 /* This is the basic code for new root creation.
 229  *
 230  * WARNING!  The order of actions in this routine is in many ways
 231  * critical.  E. g., it is essential that an error doesn't leave Guile
 232  * in a messed up state.  */
 233
 234 SCM
 235 scm_internal_cwdr (scm_catch_body_t body, void *body_data,
 236                    scm_catch_handler_t handler, void *handler_data,
 237                    SCM_STACKITEM *stack_start)
 238 {
 239 #ifdef USE_STACKJMPBUF
 240   scm_contregs static_jmpbuf;
 241 #endif
 242   int old_ints_disabled = scm_ints_disabled;
 243   SCM old_rootcont, old_winds;
 244   struct cwdr_handler_data my_handler_data;
 245   SCM answer;
 246
 247   /* Create a fresh root continuation.  */
 248   {
 249     SCM new_rootcont;
 250     SCM_NEWCELL (new_rootcont);
 251     SCM_REDEFER_INTS;
 252 #ifdef USE_STACKJMPBUF
 253     SCM_SETJMPBUF (new_rootcont, &static_jmpbuf);
 254 #else
 255     SCM_SETJMPBUF (new_rootcont,
 256                    scm_must_malloc ((long) sizeof (scm_contregs),
 257                                     "inferior root continuation"));
 258 #endif
 259     SCM_SETCAR (new_rootcont, scm_tc7_contin);
 260     SCM_DYNENV (new_rootcont) = SCM_EOL;
 261     SCM_BASE (new_rootcont) = stack_start;
 262     SCM_SEQ (new_rootcont) = ++n_dynamic_roots;
 263 #ifdef DEBUG_EXTENSIONS
 264     SCM_DFRAME (new_rootcont) = 0;
 265 #endif
 266     old_rootcont = scm_rootcont;
 267     scm_rootcont = new_rootcont;
 268     SCM_REALLOW_INTS;
 269   }
 270
 271   /* Exit caller's dynamic state.
 272    */
 273   old_winds = scm_dynwinds;
 274   scm_dowinds (SCM_EOL, scm_ilength (scm_dynwinds));
 275 #ifdef DEBUG_EXTENSIONS
 276   SCM_DFRAME (old_rootcont) = scm_last_debug_frame;
 277   scm_last_debug_frame = 0;
 278 #endif
 279
 280   {
 281     my_handler_data.run_handler = 0;
 282     answer = scm_internal_catch (SCM_BOOL_T,
 283                                  body, body_data,
 284                                  cwdr_handler, &my_handler_data);
 285   }
 286
 287   scm_dowinds (old_winds, - scm_ilength (old_winds));
 288   SCM_REDEFER_INTS;
 289 #ifdef USE_STACKCJMPBUF
 290   SCM_SETJMPBUF (scm_rootcont, NULL);
 291 #endif
 292 #ifdef DEBUG_EXTENSIONS
 293   scm_last_debug_frame = SCM_DFRAME (old_rootcont);
 294 #endif
 295   scm_rootcont = old_rootcont;
 296   SCM_REALLOW_INTS;
 297   scm_ints_disabled = old_ints_disabled;
 298
 299   /* Now run the real handler iff the body did a throw. */
 300   if (my_handler_data.run_handler)
 301     return handler (handler_data, my_handler_data.tag, my_handler_data.args);
 302   else
 303     return answer;
 304 }
 305
 306 /* The original CWDR for invoking Scheme code with a Scheme handler. */
 307
 308 static SCM
 309 cwdr (SCM proc, SCM a1, SCM args, SCM handler, SCM_STACKITEM *stack_start)
 310 {
 311   struct cwdr_body_data c;
 312
 313   c.a1 = a1;
 314   c.args = args;
 315   c.body_proc = proc;
 316
 317   return scm_internal_cwdr (cwdr_body, &c,
 318                             scm_handle_by_proc, &handler,
 319                             stack_start);
 320 }
 321
 322 SCM_PROC(s_call_with_dynamic_root, "call-with-dynamic-root", 2, 0, 0, scm_call_with_dynamic_root);
 323 SCM
 324 scm_call_with_dynamic_root (thunk, handler)
 325      SCM thunk;
 326      SCM handler;
 327 {
 328   SCM_STACKITEM stack_place;
 329
 330   return cwdr (thunk, SCM_EOL, SCM_EOL, handler, &stack_place);
 331 }
 332
 333 SCM_PROC(s_dynamic_root, "dynamic-root", 0, 0, 0, scm_dynamic_root);
 334 SCM
 335 scm_dynamic_root ()
 336 {
 337   return scm_ulong2num (SCM_SEQ (scm_root->rootcont));
 338 }
 339
 340 SCM
 341 scm_apply_with_dynamic_root (proc, a1, args, handler)
 342      SCM proc;
 343      SCM a1;
 344      SCM args;
 345      SCM handler;
 346 {
 347   SCM_STACKITEM stack_place;
 348   return cwdr (proc, a1, args, handler, &stack_place);
 349 }
 350
 351 \f
 352
 353 /* Call thunk(closure) underneath a top-level error handler.
 354  * If an error occurs, pass the exitval through err_filter and return it.
 355  * If no error occurs, return the value of thunk.
 356  */
 357
 358
 359 #ifdef _UNICOS
 360 typedef int setjmp_type;
 361 #else
 362 typedef long setjmp_type;
 363 #endif
 364
 365
 366
 367 SCM
 368 scm_call_catching_errors (thunk, err_filter, closure)
 369      SCM (*thunk)();
 370      SCM (*err_filter)();
 371      void *closure;
 372 {
 373   SCM answer;
 374   setjmp_type i;
 375 #ifdef DEBUG_EXTENSIONS
 376   SCM_DFRAME (scm_rootcont) = scm_last_debug_frame;
 377 #endif
 378   i = setjmp (SCM_JMPBUF (scm_rootcont));
 379   scm_stack_checking_enabled_p = SCM_STACK_CHECKING_P;
 380   if (!i)
 381     {
 382       scm_gc_heap_lock = 0;
 383       answer = thunk (closure);
 384     }
 385   else
 386     {
 387       scm_gc_heap_lock = 1;
 388       answer = err_filter (scm_exitval, closure);
 389     }
 390   return answer;
 391 }
 392
 393 void
 394 scm_init_root ()
 395 {
 396   scm_tc16_root = scm_make_smob_type_mfpe ("root", sizeof (struct scm_root_state),
 397                                           mark_root, NULL, print_root, NULL);
 398
 399 #include "root.x"
 400 }