libguile/root.c

   1 /*      Copyright (C) 1995,1996, 1997 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   SCM_SETGC8MARK (root);
  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 static scm_sizet free_root SCM_P ((SCM));
 101
 102 static scm_sizet
 103 free_root (root)
 104      SCM root;
 105 {
 106   scm_must_free ((char *) SCM_ROOT_STATE (root));
 107   return sizeof (scm_root_state);
 108 }
 109
 110 static int print_root SCM_P ((SCM exp, SCM port, scm_print_state *pstate));
 111
 112 static int
 113 print_root (exp, port, pstate)
 114      SCM exp;
 115      SCM port;
 116      scm_print_state *pstate;
 117 {
 118   scm_puts ("#<root ", port);
 119   scm_intprint(SCM_SEQ (SCM_ROOT_STATE (exp) -> rootcont), 16, port);
 120   scm_putc('>', port);
 121   return 1;
 122 }
 123
 124 static scm_smobfuns root_smob =
 125 {
 126   mark_root,
 127   free_root,
 128   print_root,
 129   0
 130 };
 131
 132 \f
 133
 134 SCM
 135 scm_make_root (parent)
 136      SCM parent;
 137 {
 138   SCM root;
 139   scm_root_state *root_state;
 140
 141   root_state = (scm_root_state *) scm_must_malloc (sizeof (scm_root_state),
 142                                                    "scm_make_root");
 143   if (SCM_NIMP (parent) && SCM_ROOTP (parent))
 144     {
 145       memcpy (root_state, SCM_ROOT_STATE (parent), sizeof (scm_root_state));
 146       scm_copy_fluids (root_state);
 147       root_state->parent = parent;
 148     }
 149   else
 150     {
 151       root_state->parent = SCM_BOOL_F;
 152     }
 153   SCM_NEWCELL (root);
 154   SCM_REDEFER_INTS;
 155   SCM_SETCAR (root, scm_tc16_root);
 156   SCM_SETCDR (root, root_state);
 157   root_state->handle = root;
 158   SCM_REALLOW_INTS;
 159   return root;
 160 }
 161
 162 /* {call-with-dynamic-root}
 163  *
 164  * Suspending the current thread to evaluate a thunk on the
 165  * same C stack but under a new root.
 166  *
 167  * Calls to call-with-dynamic-root return exactly once (unless
 168  * the process is somehow exitted).  */
 169
 170 /* Some questions about cwdr:
 171
 172    Couldn't the body just be a closure?  Do we really need to pass
 173    args through to it?
 174
 175    The semantics are a lot like catch's; in fact, we call
 176    scm_internal_catch to take care of that part of things.  Wouldn't
 177    it be cleaner to say that uncaught throws just disappear into the
 178    ether (or print a message to stderr), and let the caller use catch
 179    themselves if they want to?
 180
 181    -JimB */
 182
 183 #if 0
 184 SCM scm_exitval;                /* INUM with return value */
 185 #endif
 186 static int n_dynamic_roots = 0;
 187
 188
 189 /* cwdr fills out both of these structures, and then passes a pointer
 190    to them through scm_internal_catch to the cwdr_body and
 191    cwdr_handler functions, to tell them how to behave and to get
 192    information back from them.
 193
 194    A cwdr is a lot like a catch, except there is no tag (all
 195    exceptions are caught), and the body procedure takes the arguments
 196    passed to cwdr as A1 and ARGS.  The handler is also special since
 197    it is not directly run from scm_internal_catch.  It is executed
 198    outside the new dynamic root. */
 199
 200 struct cwdr_body_data {
 201   /* Arguments to pass to the cwdr body function.  */
 202   SCM a1, args;
 203
 204   /* Scheme procedure to use as body of cwdr.  */
 205   SCM body_proc;
 206 };
 207
 208 struct cwdr_handler_data {
 209   /* Do we need to run the handler? */
 210   int run_handler;
 211
 212   /* The tag and args to pass it. */
 213   SCM tag, args;
 214 };
 215
 216
 217 /* Invoke the body of a cwdr, assuming that the throw handler has
 218    already been set up.  DATA points to a struct set up by cwdr that
 219    says what proc to call, and what args to apply it to.
 220
 221    With a little thought, we could replace this with scm_body_thunk,
 222    but I don't want to mess with that at the moment.  */
 223 static SCM
 224 cwdr_body (void *data)
 225 {
 226   struct cwdr_body_data *c = (struct cwdr_body_data *) data;
 227
 228   return scm_apply (c->body_proc, c->a1, c->args);
 229 }
 230
 231 /* Record the fact that the body of the cwdr has thrown.  Record
 232    enough information to invoke the handler later when the dynamic
 233    root has been deestablished.  */
 234
 235 static SCM
 236 cwdr_handler (void *data, SCM tag, SCM args)
 237 {
 238   struct cwdr_handler_data *c = (struct cwdr_handler_data *) data;
 239
 240   c->run_handler = 1;
 241   c->tag = tag;
 242   c->args = args;
 243   return SCM_UNSPECIFIED;
 244 }
 245
 246 /* This is the basic code for new root creation.
 247  *
 248  * WARNING!  The order of actions in this routine is in many ways
 249  * critical.  E. g., it is essential that an error doesn't leave Guile
 250  * in a messed up state.  */
 251
 252 SCM
 253 scm_internal_cwdr (scm_catch_body_t body, void *body_data,
 254                    scm_catch_handler_t handler, void *handler_data,
 255                    SCM_STACKITEM *stack_start)
 256 {
 257 #ifdef USE_STACKJMPBUF
 258   scm_contregs static_jmpbuf;
 259 #endif
 260   int old_ints_disabled = scm_ints_disabled;
 261   SCM old_rootcont, old_winds;
 262   struct cwdr_handler_data my_handler_data;
 263   SCM answer;
 264
 265   /* Create a fresh root continuation.  */
 266   {
 267     SCM new_rootcont;
 268     SCM_NEWCELL (new_rootcont);
 269     SCM_REDEFER_INTS;
 270 #ifdef USE_STACKJMPBUF
 271     SCM_SETJMPBUF (new_rootcont, &static_jmpbuf);
 272 #else
 273     SCM_SETJMPBUF (new_rootcont,
 274                    scm_must_malloc ((long) sizeof (scm_contregs),
 275                                     "inferior root continuation"));
 276 #endif
 277     SCM_SETCAR (new_rootcont, scm_tc7_contin);
 278     SCM_DYNENV (new_rootcont) = SCM_EOL;
 279     SCM_BASE (new_rootcont) = stack_start;
 280     SCM_SEQ (new_rootcont) = ++n_dynamic_roots;
 281 #ifdef DEBUG_EXTENSIONS
 282     SCM_DFRAME (new_rootcont) = 0;
 283 #endif
 284     old_rootcont = scm_rootcont;
 285     scm_rootcont = new_rootcont;
 286     SCM_REALLOW_INTS;
 287   }
 288
 289   /* Exit caller's dynamic state.
 290    */
 291   old_winds = scm_dynwinds;
 292   scm_dowinds (SCM_EOL, scm_ilength (scm_dynwinds));
 293 #ifdef DEBUG_EXTENSIONS
 294   SCM_DFRAME (old_rootcont) = scm_last_debug_frame;
 295   scm_last_debug_frame = 0;
 296 #endif
 297
 298   {
 299     my_handler_data.run_handler = 0;
 300     answer = scm_internal_catch (SCM_BOOL_T,
 301                                  body, body_data,
 302                                  cwdr_handler, &my_handler_data);
 303   }
 304
 305   scm_dowinds (old_winds, - scm_ilength (old_winds));
 306   SCM_REDEFER_INTS;
 307 #ifdef USE_STACKCJMPBUF
 308   SCM_SETJMPBUF (scm_rootcont, NULL);
 309 #endif
 310 #ifdef DEBUG_EXTENSIONS
 311   scm_last_debug_frame = SCM_DFRAME (old_rootcont);
 312 #endif
 313   scm_rootcont = old_rootcont;
 314   SCM_REALLOW_INTS;
 315   scm_ints_disabled = old_ints_disabled;
 316
 317   /* Now run the real handler iff the body did a throw. */
 318   if (my_handler_data.run_handler)
 319     return handler (handler_data, my_handler_data.tag, my_handler_data.args);
 320   else
 321     return answer;
 322 }
 323
 324 /* The original CWDR for invoking Scheme code with a Scheme handler. */
 325
 326 static SCM
 327 cwdr (SCM proc, SCM a1, SCM args, SCM handler, SCM_STACKITEM *stack_start)
 328 {
 329   struct cwdr_body_data c;
 330
 331   c.a1 = a1;
 332   c.args = args;
 333   c.body_proc = proc;
 334
 335   return scm_internal_cwdr (cwdr_body, &c,
 336                             scm_handle_by_proc, &handler,
 337                             stack_start);
 338 }
 339
 340 SCM_PROC(s_call_with_dynamic_root, "call-with-dynamic-root", 2, 0, 0, scm_call_with_dynamic_root);
 341 SCM
 342 scm_call_with_dynamic_root (thunk, handler)
 343      SCM thunk;
 344      SCM handler;
 345 {
 346   SCM_STACKITEM stack_place;
 347
 348   return cwdr (thunk, SCM_EOL, SCM_EOL, handler, &stack_place);
 349 }
 350
 351 SCM_PROC(s_dynamic_root, "dynamic-root", 0, 0, 0, scm_dynamic_root);
 352 SCM
 353 scm_dynamic_root ()
 354 {
 355   return scm_ulong2num (SCM_SEQ (scm_root->rootcont));
 356 }
 357
 358 SCM
 359 scm_apply_with_dynamic_root (proc, a1, args, handler)
 360      SCM proc;
 361      SCM a1;
 362      SCM args;
 363      SCM handler;
 364 {
 365   SCM_STACKITEM stack_place;
 366   return cwdr (proc, a1, args, handler, &stack_place);
 367 }
 368
 369 \f
 370
 371 /* Call thunk(closure) underneath a top-level error handler.
 372  * If an error occurs, pass the exitval through err_filter and return it.
 373  * If no error occurs, return the value of thunk.
 374  */
 375
 376
 377 #ifdef _UNICOS
 378 typedef int setjmp_type;
 379 #else
 380 typedef long setjmp_type;
 381 #endif
 382
 383
 384
 385 SCM
 386 scm_call_catching_errors (thunk, err_filter, closure)
 387      SCM (*thunk)();
 388      SCM (*err_filter)();
 389      void *closure;
 390 {
 391   SCM answer;
 392   setjmp_type i;
 393 #ifdef DEBUG_EXTENSIONS
 394   SCM_DFRAME (scm_rootcont) = scm_last_debug_frame;
 395 #endif
 396   i = setjmp (SCM_JMPBUF (scm_rootcont));
 397   scm_stack_checking_enabled_p = SCM_STACK_CHECKING_P;
 398   if (!i)
 399     {
 400       scm_gc_heap_lock = 0;
 401       answer = thunk (closure);
 402     }
 403   else
 404     {
 405       scm_gc_heap_lock = 1;
 406       answer = err_filter (scm_exitval, closure);
 407     }
 408   return answer;
 409 }
 410
 411 void
 412 scm_init_root ()
 413 {
 414   scm_tc16_root = scm_newsmob (&root_smob);
 415 #include "root.x"
 416 }