libguile/throw.c

   1 /* Copyright (C) 1995,1996,1997,1998,2000,2001, 2003, 2004, 2006, 2008, 2009, 2010 Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public License
   5  * as published by the Free Software Foundation; either version 3 of
   6  * the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301 USA
  17  */
  18
  19
  20 \f
  21 #ifdef HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <stdio.h>
  26 #include <unistdio.h>
  27 #include "libguile/_scm.h"
  28 #include "libguile/smob.h"
  29 #include "libguile/eval.h"
  30 #include "libguile/eq.h"
  31 #include "libguile/control.h"
  32 #include "libguile/deprecation.h"
  33 #include "libguile/backtrace.h"
  34 #include "libguile/debug.h"
  35 #include "libguile/stackchk.h"
  36 #include "libguile/stacks.h"
  37 #include "libguile/fluids.h"
  38 #include "libguile/ports.h"
  39 #include "libguile/validate.h"
  40 #include "libguile/vm.h"
  41 #include "libguile/throw.h"
  42 #include "libguile/init.h"
  43 #include "libguile/strings.h"
  44
  45 #include "libguile/private-options.h"
  46
  47
  48 /* Pleasantly enough, the guts of catch are defined in Scheme, in terms of
  49    prompt, abort, and the %exception-handler fluid. This file just provides
  50    shims so that it's easy to have catch functionality from C.
  51
  52    All of these function names and prototypes carry a fair bit of historical
  53    baggage. */
  54
  55
  56 #define CACHE_VAR(var,name)                                             \
  57   static SCM var = SCM_BOOL_F;                                          \
  58   if (scm_is_false (var))                                               \
  59     {                                                                   \
  60       var = scm_module_variable (scm_the_root_module (),                \
  61                                  scm_from_locale_symbol (name));        \
  62       if (scm_is_false (var))                                           \
  63         abort ();                                                       \
  64     }
  65
  66 \f
  67
  68 SCM
  69 scm_catch (SCM key, SCM thunk, SCM handler)
  70 {
  71   CACHE_VAR (var, "catch");
  72
  73   return scm_call_3 (scm_variable_ref (var), key, thunk, handler);
  74 }
  75
  76 SCM
  77 scm_catch_with_pre_unwind_handler (SCM key, SCM thunk, SCM handler,
  78                                    SCM pre_unwind_handler)
  79 {
  80   if (SCM_UNBNDP (pre_unwind_handler))
  81     return scm_catch (key, thunk, handler);
  82   else
  83     {
  84       CACHE_VAR (var, "catch");
  85
  86       return scm_call_4 (scm_variable_ref (var), key, thunk, handler,
  87                          pre_unwind_handler);
  88     }
  89 }
  90
  91 SCM
  92 scm_with_throw_handler (SCM key, SCM thunk, SCM handler)
  93 {
  94   CACHE_VAR (var, "with-throw-handler");
  95
  96   return scm_call_3 (scm_variable_ref (var), key, thunk, handler);
  97 }
  98
  99 SCM
 100 scm_throw (SCM key, SCM args)
 101 {
 102   CACHE_VAR (var, "throw");
 103
 104   return scm_apply_1 (scm_variable_ref (var), key, args);
 105 }
 106
 107 \f
 108
 109 /* Now some support for C bodies and catch handlers */
 110
 111 static scm_t_bits tc16_catch_closure;
 112
 113 enum {
 114   CATCH_CLOSURE_BODY,
 115   CATCH_CLOSURE_HANDLER
 116 };
 117
 118 static SCM
 119 make_catch_body_closure (scm_t_catch_body body, void *body_data)
 120 {
 121   SCM ret;
 122   SCM_NEWSMOB2 (ret, tc16_catch_closure, body, body_data);
 123   SCM_SET_SMOB_FLAGS (ret, CATCH_CLOSURE_BODY);
 124   return ret;
 125 }
 126
 127 static SCM
 128 make_catch_handler_closure (scm_t_catch_handler handler, void *handler_data)
 129 {
 130   SCM ret;
 131   SCM_NEWSMOB2 (ret, tc16_catch_closure, handler, handler_data);
 132   SCM_SET_SMOB_FLAGS (ret, CATCH_CLOSURE_HANDLER);
 133   return ret;
 134 }
 135
 136 static SCM
 137 apply_catch_closure (SCM clo, SCM args)
 138 {
 139   void *data = (void*)SCM_SMOB_DATA_2 (clo);
 140
 141   switch (SCM_SMOB_FLAGS (clo))
 142     {
 143     case CATCH_CLOSURE_BODY:
 144       {
 145         scm_t_catch_body body = (void*)SCM_SMOB_DATA (clo);
 146         return body (data);
 147       }
 148     case CATCH_CLOSURE_HANDLER:
 149       {
 150         scm_t_catch_handler handler = (void*)SCM_SMOB_DATA (clo);
 151         return handler (data, scm_car (args), scm_cdr (args));
 152       }
 153     default:
 154       abort ();
 155     }
 156 }
 157
 158 /* TAG is the catch tag.  Typically, this is a symbol, but this
 159    function doesn't actually care about that.
 160
 161    BODY is a pointer to a C function which runs the body of the catch;
 162    this is the code you can throw from.  We call it like this:
 163       BODY (BODY_DATA)
 164    where:
 165       BODY_DATA is just the BODY_DATA argument we received; we pass it
 166          through to BODY as its first argument.  The caller can make
 167          BODY_DATA point to anything useful that BODY might need.
 168
 169    HANDLER is a pointer to a C function to deal with a throw to TAG,
 170    should one occur.  We call it like this:
 171       HANDLER (HANDLER_DATA, THROWN_TAG, THROW_ARGS)
 172    where
 173       HANDLER_DATA is the HANDLER_DATA argument we recevied; it's the
 174          same idea as BODY_DATA above.
 175       THROWN_TAG is the tag that the user threw to; usually this is
 176          TAG, but it could be something else if TAG was #t (i.e., a
 177          catch-all), or the user threw to a jmpbuf.
 178       THROW_ARGS is the list of arguments the user passed to the THROW
 179          function, after the tag.
 180
 181    BODY_DATA is just a pointer we pass through to BODY.  HANDLER_DATA
 182    is just a pointer we pass through to HANDLER.  We don't actually
 183    use either of those pointers otherwise ourselves.  The idea is
 184    that, if our caller wants to communicate something to BODY or
 185    HANDLER, it can pass a pointer to it as MUMBLE_DATA, which BODY and
 186    HANDLER can then use.  Think of it as a way to make BODY and
 187    HANDLER closures, not just functions; MUMBLE_DATA points to the
 188    enclosed variables.
 189
 190    Of course, it's up to the caller to make sure that any data a
 191    MUMBLE_DATA needs is protected from GC.  A common way to do this is
 192    to make MUMBLE_DATA a pointer to data stored in an automatic
 193    structure variable; since the collector must scan the stack for
 194    references anyway, this assures that any references in MUMBLE_DATA
 195    will be found.  */
 196
 197 SCM
 198 scm_c_catch (SCM tag,
 199              scm_t_catch_body body, void *body_data,
 200              scm_t_catch_handler handler, void *handler_data,
 201              scm_t_catch_handler pre_unwind_handler, void *pre_unwind_handler_data)
 202 {
 203   SCM sbody, shandler, spre_unwind_handler;
 204
 205   sbody = make_catch_body_closure (body, body_data);
 206   shandler = make_catch_handler_closure (handler, handler_data);
 207   if (pre_unwind_handler)
 208     spre_unwind_handler = make_catch_handler_closure (pre_unwind_handler,
 209                                                       pre_unwind_handler_data);
 210   else
 211     spre_unwind_handler = SCM_UNDEFINED;
 212
 213   return scm_catch_with_pre_unwind_handler (tag, sbody, shandler,
 214                                             spre_unwind_handler);
 215 }
 216
 217 SCM
 218 scm_internal_catch (SCM tag,
 219                     scm_t_catch_body body, void *body_data,
 220                     scm_t_catch_handler handler, void *handler_data)
 221 {
 222   return scm_c_catch (tag,
 223                       body, body_data,
 224                       handler, handler_data,
 225                       NULL, NULL);
 226 }
 227
 228
 229 SCM
 230 scm_c_with_throw_handler (SCM tag,
 231                           scm_t_catch_body body,
 232                           void *body_data,
 233                           scm_t_catch_handler handler,
 234                           void *handler_data,
 235                           int lazy_catch_p)
 236 {
 237   SCM sbody, shandler;
 238
 239   if (lazy_catch_p)
 240     scm_c_issue_deprecation_warning
 241       ("The LAZY_CATCH_P argument to `scm_c_with_throw_handler' is no longer.\n"
 242        "supported. Instead the handler will be invoked from within the dynamic\n"
 243        "context of the corresponding `throw'.\n"
 244        "\nTHIS COULD CHANGE YOUR PROGRAM'S BEHAVIOR.\n\n"
 245        "Please modify your program to pass 0 as the LAZY_CATCH_P argument,\n"
 246        "and adapt it (if necessary) to expect to be within the dynamic context\n"
 247        "of the throw.");
 248
 249   sbody = make_catch_body_closure (body, body_data);
 250   shandler = make_catch_handler_closure (handler, handler_data);
 251
 252   return scm_with_throw_handler (tag, sbody, shandler);
 253 }
 254
 255 \f
 256 /* scm_internal_stack_catch
 257    Use this one if you want debugging information to be stored in
 258    scm_the_last_stack_fluid_var on error. */
 259
 260 static SCM
 261 ss_handler (void *data SCM_UNUSED, SCM tag, SCM throw_args)
 262 {
 263   /* Save the stack */
 264   scm_fluid_set_x (SCM_VARIABLE_REF (scm_the_last_stack_fluid_var),
 265                    scm_make_stack (SCM_BOOL_T, SCM_EOL));
 266   /* Throw the error */
 267   return scm_throw (tag, throw_args);
 268 }
 269
 270 struct cwss_data
 271 {
 272   SCM tag;
 273   scm_t_catch_body body;
 274   void *data;
 275 };
 276
 277 static SCM
 278 cwss_body (void *data)
 279 {
 280   struct cwss_data *d = data;
 281   return scm_c_with_throw_handler (d->tag, d->body, d->data, ss_handler, NULL, 0);
 282 }
 283
 284 SCM
 285 scm_internal_stack_catch (SCM tag,
 286                           scm_t_catch_body body,
 287                           void *body_data,
 288                           scm_t_catch_handler handler,
 289                           void *handler_data)
 290 {
 291   struct cwss_data d;
 292   d.tag = tag;
 293   d.body = body;
 294   d.data = body_data;
 295   return scm_internal_catch (tag, cwss_body, &d, handler, handler_data);
 296 }
 297
 298
 299 \f
 300 /* body and handler functions for use with any of the above catch variants */
 301
 302 /* This is a body function you can pass to scm_internal_catch if you
 303    want the body to be like Scheme's `catch' --- a thunk.
 304
 305    BODY_DATA is a pointer to a scm_body_thunk_data structure, which
 306    contains the Scheme procedure to invoke as the body, and the tag
 307    we're catching.  */
 308
 309 SCM
 310 scm_body_thunk (void *body_data)
 311 {
 312   struct scm_body_thunk_data *c = (struct scm_body_thunk_data *) body_data;
 313
 314   return scm_call_0 (c->body_proc);
 315 }
 316
 317
 318 /* This is a handler function you can pass to scm_internal_catch if
 319    you want the handler to act like Scheme's catch: (throw TAG ARGS ...)
 320    applies a handler procedure to (TAG ARGS ...).
 321
 322    If the user does a throw to this catch, this function runs a
 323    handler procedure written in Scheme.  HANDLER_DATA is a pointer to
 324    an SCM variable holding the Scheme procedure object to invoke.  It
 325    ought to be a pointer to an automatic variable (i.e., one living on
 326    the stack), or the procedure object should be otherwise protected
 327    from GC.  */
 328 SCM
 329 scm_handle_by_proc (void *handler_data, SCM tag, SCM throw_args)
 330 {
 331   SCM *handler_proc_p = (SCM *) handler_data;
 332
 333   return scm_apply_1 (*handler_proc_p, tag, throw_args);
 334 }
 335
 336 /* SCM_HANDLE_BY_PROC_CATCHING_ALL is like SCM_HANDLE_BY_PROC but
 337    catches all throws that the handler might emit itself.  The handler
 338    used for these `secondary' throws is SCM_HANDLE_BY_MESSAGE_NO_EXIT.  */
 339
 340 struct hbpca_data {
 341   SCM proc;
 342   SCM args;
 343 };
 344
 345 static SCM
 346 hbpca_body (void *body_data)
 347 {
 348   struct hbpca_data *data = (struct hbpca_data *)body_data;
 349   return scm_apply_0 (data->proc, data->args);
 350 }
 351
 352 SCM
 353 scm_handle_by_proc_catching_all (void *handler_data, SCM tag, SCM throw_args)
 354 {
 355   SCM *handler_proc_p = (SCM *) handler_data;
 356   struct hbpca_data data;
 357   data.proc = *handler_proc_p;
 358   data.args = scm_cons (tag, throw_args);
 359
 360   return scm_internal_catch (SCM_BOOL_T,
 361                              hbpca_body, &data,
 362                              scm_handle_by_message_noexit, NULL);
 363 }
 364
 365 /* Derive the an exit status from the arguments to (quit ...).  */
 366 int
 367 scm_exit_status (SCM args)
 368 {
 369   if (!SCM_NULL_OR_NIL_P (args))
 370     {
 371       SCM cqa = SCM_CAR (args);
 372
 373       if (scm_is_integer (cqa))
 374         return (scm_to_int (cqa));
 375       else if (scm_is_false (cqa))
 376         return 1;
 377     }
 378   return 0;
 379 }
 380
 381
 382 static void
 383 handler_message (void *handler_data, SCM tag, SCM args)
 384 {
 385   char *prog_name = (char *) handler_data;
 386   SCM p = scm_current_error_port ();
 387
 388   if (scm_ilength (args) == 4)
 389     {
 390       SCM stack   = scm_make_stack (SCM_BOOL_T, SCM_EOL);
 391       SCM subr    = SCM_CAR (args);
 392       SCM message = SCM_CADR (args);
 393       SCM parts   = SCM_CADDR (args);
 394       SCM rest    = SCM_CADDDR (args);
 395
 396       if (SCM_BACKTRACE_P && scm_is_true (stack))
 397         {
 398           SCM highlights;
 399
 400           if (scm_is_eq (tag, scm_arg_type_key)
 401               || scm_is_eq (tag, scm_out_of_range_key))
 402             highlights = rest;
 403           else
 404             highlights = SCM_EOL;
 405
 406           scm_puts ("Backtrace:\n", p);
 407           scm_display_backtrace_with_highlights (stack, p,
 408                                                  SCM_BOOL_F, SCM_BOOL_F,
 409                                                  highlights);
 410           scm_newline (p);
 411         }
 412       scm_i_display_error (stack, p, subr, message, parts, rest);
 413     }
 414   else
 415     {
 416       if (! prog_name)
 417         prog_name = "guile";
 418
 419       scm_puts (prog_name, p);
 420       scm_puts (": ", p);
 421
 422       scm_puts ("uncaught throw to ", p);
 423       scm_prin1 (tag, p, 0);
 424       scm_puts (": ", p);
 425       scm_prin1 (args, p, 1);
 426       scm_putc ('\n', p);
 427     }
 428 }
 429
 430
 431 /* This is a handler function to use if you want scheme to print a
 432    message and die.  Useful for dealing with throws to uncaught keys
 433    at the top level.
 434
 435    At boot time, we establish a catch-all that uses this as its handler.
 436    1) If the user wants something different, they can use (catch #t
 437    ...) to do what they like.
 438    2) Outside the context of a read-eval-print loop, there isn't
 439    anything else good to do; libguile should not assume the existence
 440    of a read-eval-print loop.
 441    3) Given that we shouldn't do anything complex, it's much more
 442    robust to do it in C code.
 443
 444    HANDLER_DATA, if non-zero, is assumed to be a char * pointing to a
 445    message header to print; if zero, we use "guile" instead.  That
 446    text is followed by a colon, then the message described by ARGS.  */
 447
 448 /* Dirk:FIXME:: The name of the function should make clear that the
 449  * application gets terminated.
 450  */
 451
 452 SCM
 453 scm_handle_by_message (void *handler_data, SCM tag, SCM args)
 454 {
 455   if (scm_is_true (scm_eq_p (tag, scm_from_locale_symbol ("quit"))))
 456     exit (scm_exit_status (args));
 457
 458   handler_message (handler_data, tag, args);
 459   scm_i_pthread_exit (NULL);
 460
 461   /* this point not reached, but suppress gcc warning about no return value
 462      in case scm_i_pthread_exit isn't marked as "noreturn" (which seemed not
 463      to be the case on cygwin for instance) */
 464   return SCM_BOOL_F;
 465 }
 466
 467
 468 /* This is just like scm_handle_by_message, but it doesn't exit; it
 469    just returns #f.  It's useful in cases where you don't really know
 470    enough about the body to handle things in a better way, but don't
 471    want to let throws fall off the bottom of the wind list.  */
 472 SCM
 473 scm_handle_by_message_noexit (void *handler_data, SCM tag, SCM args)
 474 {
 475   if (scm_is_true (scm_eq_p (tag, scm_from_locale_symbol ("quit"))))
 476     exit (scm_exit_status (args));
 477
 478   handler_message (handler_data, tag, args);
 479
 480   return SCM_BOOL_F;
 481 }
 482
 483
 484 SCM
 485 scm_handle_by_throw (void *handler_data SCM_UNUSED, SCM tag, SCM args)
 486 {
 487   scm_ithrow (tag, args, 1);
 488   return SCM_UNSPECIFIED;  /* never returns */
 489 }
 490
 491 SCM
 492 scm_ithrow (SCM key, SCM args, int noreturn SCM_UNUSED)
 493 {
 494   return scm_throw (key, args);
 495 }
 496
 497 /* Unfortunately we have to support catch and throw before boot-9 has, um,
 498    booted. So here are lame versions, which will get replaced with their scheme
 499    equivalents. */
 500
 501 SCM_SYMBOL (sym_pre_init_catch_tag, "%pre-init-catch-tag");
 502
 503 static SCM
 504 pre_init_catch (SCM tag, SCM thunk, SCM handler, SCM pre_unwind_handler)
 505 {
 506   SCM vm, prompt, res;
 507
 508   /* Only handle catch-alls without pre-unwind handlers */
 509   if (!SCM_UNBNDP (pre_unwind_handler))
 510     abort ();
 511   if (scm_is_false (scm_eqv_p (tag, SCM_BOOL_T)))
 512     abort ();
 513
 514   vm = scm_the_vm ();
 515   prompt = scm_c_make_prompt (sym_pre_init_catch_tag,
 516                               SCM_VM_DATA (vm)->fp, SCM_VM_DATA (vm)->sp,
 517                               SCM_VM_DATA (vm)->ip, 1, -1, scm_i_dynwinds ());
 518   scm_i_set_dynwinds (scm_cons (prompt, SCM_PROMPT_DYNWINDS (prompt)));
 519
 520   if (SCM_PROMPT_SETJMP (prompt))
 521     {
 522       /* nonlocal exit */
 523       SCM args = scm_i_prompt_pop_abort_args_x (prompt);
 524       /* cdr past the continuation */
 525       return scm_apply_0 (handler, scm_cdr (args));
 526     }
 527
 528   res = scm_call_0 (thunk);
 529   scm_i_set_dynwinds (scm_cdr (scm_i_dynwinds ()));
 530
 531   return res;
 532 }
 533
 534 static SCM
 535 pre_init_throw (SCM args)
 536 {
 537   return scm_at_abort (sym_pre_init_catch_tag, args);
 538 }
 539
 540 void
 541 scm_init_throw ()
 542 {
 543   tc16_catch_closure = scm_make_smob_type ("catch-closure", 0);
 544   scm_set_smob_apply (tc16_catch_closure, apply_catch_closure, 0, 0, 1);
 545
 546   scm_c_define ("catch", scm_c_make_gsubr ("catch", 3, 1, 0, pre_init_catch));
 547   scm_c_define ("throw", scm_c_make_gsubr ("throw", 0, 0, 1, pre_init_throw));
 548
 549 #include "libguile/throw.x"
 550 }
 551
 552 /*
 553   Local Variables:
 554   c-file-style: "gnu"
 555   End:
 556 */