gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
   4    1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
   5    2009, 2010, 2011 Free Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23 #include "exceptions.h"
  24 #include "breakpoint.h"
  25 #include "target.h"
  26 #include "inferior.h"
  27 #include "annotate.h"
  28 #include "ui-out.h"
  29 #include "gdb_assert.h"
  30 #include "gdb_string.h"
  31 #include "serial.h"
  32 #include "gdbthread.h"
  33
  34 const struct gdb_exception exception_none = { 0, GDB_NO_ERROR, NULL };
  35
  36 /* Possible catcher states.  */
  37 enum catcher_state {
  38   /* Initial state, a new catcher has just been created.  */
  39   CATCHER_CREATED,
  40   /* The catch code is running.  */
  41   CATCHER_RUNNING,
  42   CATCHER_RUNNING_1,
  43   /* The catch code threw an exception.  */
  44   CATCHER_ABORTING
  45 };
  46
  47 /* Possible catcher actions.  */
  48 enum catcher_action {
  49   CATCH_ITER,
  50   CATCH_ITER_1,
  51   CATCH_THROWING
  52 };
  53
  54 struct catcher
  55 {
  56   enum catcher_state state;
  57   /* Jump buffer pointing back at the exception handler.  */
  58   EXCEPTIONS_SIGJMP_BUF buf;
  59   /* Status buffer belonging to the exception handler.  */
  60   volatile struct gdb_exception *exception;
  61   /* Saved/current state.  */
  62   int mask;
  63   struct cleanup *saved_cleanup_chain;
  64   /* Back link.  */
  65   struct catcher *prev;
  66 };
  67
  68 /* Where to go for throw_exception().  */
  69 static struct catcher *current_catcher;
  70
  71 /* Return length of current_catcher list.  */
  72
  73 static int
  74 catcher_list_size (void)
  75 {
  76   int size;
  77   struct catcher *catcher;
  78
  79   for (size = 0, catcher = current_catcher;
  80        catcher != NULL;
  81        catcher = catcher->prev)
  82     ++size;
  83
  84   return size;
  85 }
  86
  87 EXCEPTIONS_SIGJMP_BUF *
  88 exceptions_state_mc_init (volatile struct gdb_exception *exception,
  89                           return_mask mask)
  90 {
  91   struct catcher *new_catcher = XZALLOC (struct catcher);
  92
  93   /* Start with no exception, save it's address.  */
  94   exception->reason = 0;
  95   exception->error = GDB_NO_ERROR;
  96   exception->message = NULL;
  97   new_catcher->exception = exception;
  98
  99   new_catcher->mask = mask;
 100
 101   /* Prevent error/quit during FUNC from calling cleanups established
 102      prior to here.  */
 103   new_catcher->saved_cleanup_chain = save_cleanups ();
 104
 105   /* Push this new catcher on the top.  */
 106   new_catcher->prev = current_catcher;
 107   current_catcher = new_catcher;
 108   new_catcher->state = CATCHER_CREATED;
 109
 110   return &new_catcher->buf;
 111 }
 112
 113 static void
 114 catcher_pop (void)
 115 {
 116   struct catcher *old_catcher = current_catcher;
 117
 118   current_catcher = old_catcher->prev;
 119
 120   /* Restore the cleanup chain, the error/quit messages, and the uiout
 121      builder, to their original states.  */
 122
 123   restore_cleanups (old_catcher->saved_cleanup_chain);
 124
 125   xfree (old_catcher);
 126 }
 127
 128 /* Catcher state machine.  Returns non-zero if the m/c should be run
 129    again, zero if it should abort.  */
 130
 131 static int
 132 exceptions_state_mc (enum catcher_action action)
 133 {
 134   switch (current_catcher->state)
 135     {
 136     case CATCHER_CREATED:
 137       switch (action)
 138         {
 139         case CATCH_ITER:
 140           /* Allow the code to run the catcher.  */
 141           current_catcher->state = CATCHER_RUNNING;
 142           return 1;
 143         default:
 144           internal_error (__FILE__, __LINE__, _("bad state"));
 145         }
 146     case CATCHER_RUNNING:
 147       switch (action)
 148         {
 149         case CATCH_ITER:
 150           /* No error/quit has occured.  Just clean up.  */
 151           catcher_pop ();
 152           return 0;
 153         case CATCH_ITER_1:
 154           current_catcher->state = CATCHER_RUNNING_1;
 155           return 1;
 156         case CATCH_THROWING:
 157           current_catcher->state = CATCHER_ABORTING;
 158           /* See also throw_exception.  */
 159           return 1;
 160         default:
 161           internal_error (__FILE__, __LINE__, _("bad switch"));
 162         }
 163     case CATCHER_RUNNING_1:
 164       switch (action)
 165         {
 166         case CATCH_ITER:
 167           /* The did a "break" from the inner while loop.  */
 168           catcher_pop ();
 169           return 0;
 170         case CATCH_ITER_1:
 171           current_catcher->state = CATCHER_RUNNING;
 172           return 0;
 173         case CATCH_THROWING:
 174           current_catcher->state = CATCHER_ABORTING;
 175           /* See also throw_exception.  */
 176           return 1;
 177         default:
 178           internal_error (__FILE__, __LINE__, _("bad switch"));
 179         }
 180     case CATCHER_ABORTING:
 181       switch (action)
 182         {
 183         case CATCH_ITER:
 184           {
 185             struct gdb_exception exception = *current_catcher->exception;
 186
 187             if (current_catcher->mask & RETURN_MASK (exception.reason))
 188               {
 189                 /* Exit normally if this catcher can handle this
 190                    exception.  The caller analyses the func return
 191                    values.  */
 192                 catcher_pop ();
 193                 return 0;
 194               }
 195             /* The caller didn't request that the event be caught,
 196                relay the event to the next containing
 197                catch_errors().  */
 198             catcher_pop ();
 199             throw_exception (exception);
 200           }
 201         default:
 202           internal_error (__FILE__, __LINE__, _("bad state"));
 203         }
 204     default:
 205       internal_error (__FILE__, __LINE__, _("bad switch"));
 206     }
 207 }
 208
 209 int
 210 exceptions_state_mc_action_iter (void)
 211 {
 212   return exceptions_state_mc (CATCH_ITER);
 213 }
 214
 215 int
 216 exceptions_state_mc_action_iter_1 (void)
 217 {
 218   return exceptions_state_mc (CATCH_ITER_1);
 219 }
 220
 221 /* Return EXCEPTION to the nearest containing catch_errors().  */
 222
 223 void
 224 throw_exception (struct gdb_exception exception)
 225 {
 226   quit_flag = 0;
 227   immediate_quit = 0;
 228
 229   do_cleanups (ALL_CLEANUPS);
 230
 231   /* Jump to the containing catch_errors() call, communicating REASON
 232      to that call via setjmp's return value.  Note that REASON can't
 233      be zero, by definition in defs.h.  */
 234   exceptions_state_mc (CATCH_THROWING);
 235   *current_catcher->exception = exception;
 236   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 237 }
 238
 239 void
 240 deprecated_throw_reason (enum return_reason reason)
 241 {
 242   struct gdb_exception exception;
 243
 244   memset (&exception, 0, sizeof exception);
 245
 246   exception.reason = reason;
 247   switch (reason)
 248     {
 249     case RETURN_QUIT:
 250       break;
 251     case RETURN_ERROR:
 252       exception.error = GENERIC_ERROR;
 253       break;
 254     default:
 255       internal_error (__FILE__, __LINE__, _("bad switch"));
 256     }
 257
 258   throw_exception (exception);
 259 }
 260
 261 static void
 262 print_flush (void)
 263 {
 264   struct serial *gdb_stdout_serial;
 265
 266   if (deprecated_error_begin_hook)
 267     deprecated_error_begin_hook ();
 268   target_terminal_ours ();
 269
 270   /* We want all output to appear now, before we print the error.  We
 271      have 3 levels of buffering we have to flush (it's possible that
 272      some of these should be changed to flush the lower-level ones
 273      too):  */
 274
 275   /* 1.  The _filtered buffer.  */
 276   wrap_here ("");
 277
 278   /* 2.  The stdio buffer.  */
 279   gdb_flush (gdb_stdout);
 280   gdb_flush (gdb_stderr);
 281
 282   /* 3.  The system-level buffer.  */
 283   gdb_stdout_serial = serial_fdopen (1);
 284   if (gdb_stdout_serial)
 285     {
 286       serial_drain_output (gdb_stdout_serial);
 287       serial_un_fdopen (gdb_stdout_serial);
 288     }
 289
 290   annotate_error_begin ();
 291 }
 292
 293 static void
 294 print_exception (struct ui_file *file, struct gdb_exception e)
 295 {
 296   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 297      as that way the MI's behavior is preserved.  */
 298   const char *start;
 299   const char *end;
 300
 301   for (start = e.message; start != NULL; start = end)
 302     {
 303       end = strchr (start, '\n');
 304       if (end == NULL)
 305         fputs_filtered (start, file);
 306       else
 307         {
 308           end++;
 309           ui_file_write (file, start, end - start);
 310         }
 311     }
 312   fprintf_filtered (file, "\n");
 313
 314   /* Now append the annotation.  */
 315   switch (e.reason)
 316     {
 317     case RETURN_QUIT:
 318       annotate_quit ();
 319       break;
 320     case RETURN_ERROR:
 321       /* Assume that these are all errors.  */
 322       annotate_error ();
 323       break;
 324     default:
 325       internal_error (__FILE__, __LINE__, _("Bad switch."));
 326     }
 327 }
 328
 329 void
 330 exception_print (struct ui_file *file, struct gdb_exception e)
 331 {
 332   if (e.reason < 0 && e.message != NULL)
 333     {
 334       print_flush ();
 335       print_exception (file, e);
 336     }
 337 }
 338
 339 void
 340 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 341                    const char *prefix, ...)
 342 {
 343   if (e.reason < 0 && e.message != NULL)
 344     {
 345       va_list args;
 346
 347       print_flush ();
 348
 349       /* Print the prefix.  */
 350       va_start (args, prefix);
 351       vfprintf_filtered (file, prefix, args);
 352       va_end (args);
 353
 354       print_exception (file, e);
 355     }
 356 }
 357
 358 static void
 359 print_any_exception (struct ui_file *file, const char *prefix,
 360                      struct gdb_exception e)
 361 {
 362   if (e.reason < 0 && e.message != NULL)
 363     {
 364       target_terminal_ours ();
 365       wrap_here ("");           /* Force out any buffered output.  */
 366       gdb_flush (gdb_stdout);
 367       annotate_error_begin ();
 368
 369       /* Print the prefix.  */
 370       if (prefix != NULL && prefix[0] != '\0')
 371         fputs_filtered (prefix, file);
 372       print_exception (file, e);
 373     }
 374 }
 375
 376 /* A stack of exception messages.
 377    This is needed to handle nested calls to throw_it: we don't want to
 378    xfree space for a message before it's used.
 379    This can happen if we throw an exception during a cleanup:
 380    An outer TRY_CATCH may have an exception message it wants to print,
 381    but while doing cleanups further calls to throw_it are made.
 382
 383    This is indexed by the size of the current_catcher list.
 384    It is a dynamically allocated array so that we don't care how deeply
 385    GDB nests its TRY_CATCHs.  */
 386 static char **exception_messages;
 387
 388 /* The number of currently allocated entries in exception_messages.  */
 389 static int exception_messages_size;
 390
 391 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 392 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 393           va_list ap)
 394 {
 395   struct gdb_exception e;
 396   char *new_message;
 397   int depth = catcher_list_size ();
 398
 399   gdb_assert (depth > 0);
 400
 401   /* Note: The new message may use an old message's text.  */
 402   new_message = xstrvprintf (fmt, ap);
 403
 404   if (depth > exception_messages_size)
 405     {
 406       int old_size = exception_messages_size;
 407
 408       exception_messages_size = depth + 10;
 409       exception_messages = (char **) xrealloc (exception_messages,
 410                                                exception_messages_size
 411                                                * sizeof (char *));
 412       memset (exception_messages + old_size, 0,
 413               (exception_messages_size - old_size) * sizeof (char *));
 414     }
 415
 416   xfree (exception_messages[depth - 1]);
 417   exception_messages[depth - 1] = new_message;
 418
 419   /* Create the exception.  */
 420   e.reason = reason;
 421   e.error = error;
 422   e.message = new_message;
 423
 424   /* Throw the exception.  */
 425   throw_exception (e);
 426 }
 427
 428 void
 429 throw_verror (enum errors error, const char *fmt, va_list ap)
 430 {
 431   throw_it (RETURN_ERROR, error, fmt, ap);
 432 }
 433
 434 void
 435 throw_vfatal (const char *fmt, va_list ap)
 436 {
 437   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 438 }
 439
 440 void
 441 throw_error (enum errors error, const char *fmt, ...)
 442 {
 443   va_list args;
 444
 445   va_start (args, fmt);
 446   throw_it (RETURN_ERROR, error, fmt, args);
 447   va_end (args);
 448 }
 449
 450 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 451    handler.  If an exception (enum return_reason) is thrown using
 452    throw_exception() than all cleanups installed since
 453    catch_exceptions() was entered are invoked, the (-ve) exception
 454    value is then returned by catch_exceptions.  If FUNC() returns
 455    normally (with a positive or zero return value) then that value is
 456    returned by catch_exceptions().  It is an internal_error() for
 457    FUNC() to return a negative value.
 458
 459    See exceptions.h for further usage details.
 460
 461    Must not be called with immediate_quit in effect (bad things might
 462    happen, say we got a signal in the middle of a memcpy to quit_return).
 463    This is an OK restriction; with very few exceptions immediate_quit can
 464    be replaced by judicious use of QUIT.  */
 465
 466 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 467    error() et al. could maintain a set of flags that indicate the
 468    current state of each of the longjmp buffers.  This would give the
 469    longjmp code the chance to detect a longjmp botch (before it gets
 470    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 471    code also randomly used a SET_TOP_LEVEL macro that directly
 472    initialized the longjmp buffers.  */
 473
 474 int
 475 catch_exceptions (struct ui_out *uiout,
 476                   catch_exceptions_ftype *func,
 477                   void *func_args,
 478                   return_mask mask)
 479 {
 480   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 481 }
 482
 483 int
 484 catch_exceptions_with_msg (struct ui_out *func_uiout,
 485                            catch_exceptions_ftype *func,
 486                            void *func_args,
 487                            char **gdberrmsg,
 488                            return_mask mask)
 489 {
 490   volatile struct gdb_exception exception;
 491   volatile int val = 0;
 492   struct ui_out *saved_uiout;
 493
 494   /* Save and override the global ``struct ui_out'' builder.  */
 495   saved_uiout = current_uiout;
 496   current_uiout = func_uiout;
 497
 498   TRY_CATCH (exception, RETURN_MASK_ALL)
 499     {
 500       val = (*func) (current_uiout, func_args);
 501     }
 502
 503   /* Restore the global builder.  */
 504   current_uiout = saved_uiout;
 505
 506   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 507     {
 508       /* The caller didn't request that the event be caught.
 509          Rethrow.  */
 510       throw_exception (exception);
 511     }
 512
 513   print_any_exception (gdb_stderr, NULL, exception);
 514   gdb_assert (val >= 0);
 515   gdb_assert (exception.reason <= 0);
 516   if (exception.reason < 0)
 517     {
 518       /* If caller wants a copy of the low-level error message, make
 519          one.  This is used in the case of a silent error whereby the
 520          caller may optionally want to issue the message.  */
 521       if (gdberrmsg != NULL)
 522         {
 523           if (exception.message != NULL)
 524             *gdberrmsg = xstrdup (exception.message);
 525           else
 526             *gdberrmsg = NULL;
 527         }
 528       return exception.reason;
 529     }
 530   return val;
 531 }
 532
 533 /* This function is superseded by catch_exceptions().  */
 534
 535 int
 536 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 537               return_mask mask)
 538 {
 539   volatile int val = 0;
 540   volatile struct gdb_exception exception;
 541   struct ui_out *saved_uiout;
 542
 543   /* Save the global ``struct ui_out'' builder.  */
 544   saved_uiout = current_uiout;
 545
 546   TRY_CATCH (exception, RETURN_MASK_ALL)
 547     {
 548       val = func (func_args);
 549     }
 550
 551   /* Restore the global builder.  */
 552   current_uiout = saved_uiout;
 553
 554   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 555     {
 556       /* The caller didn't request that the event be caught.
 557          Rethrow.  */
 558       throw_exception (exception);
 559     }
 560
 561   print_any_exception (gdb_stderr, errstring, exception);
 562   if (exception.reason != 0)
 563     return 0;
 564   return val;
 565 }
 566
 567 int
 568 catch_command_errors (catch_command_errors_ftype * command,
 569                       char *arg, int from_tty, return_mask mask)
 570 {
 571   volatile struct gdb_exception e;
 572
 573   TRY_CATCH (e, mask)
 574     {
 575       command (arg, from_tty);
 576     }
 577   print_any_exception (gdb_stderr, NULL, e);
 578   if (e.reason < 0)
 579     return 0;
 580   return 1;
 581 }