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 EXCEPTIONS_SIGJMP_BUF *
  72 exceptions_state_mc_init (volatile struct gdb_exception *exception,
  73                           return_mask mask)
  74 {
  75   struct catcher *new_catcher = XZALLOC (struct catcher);
  76
  77   /* Start with no exception, save it's address.  */
  78   exception->reason = 0;
  79   exception->error = GDB_NO_ERROR;
  80   exception->message = NULL;
  81   new_catcher->exception = exception;
  82
  83   new_catcher->mask = mask;
  84
  85   /* Prevent error/quit during FUNC from calling cleanups established
  86      prior to here.  */
  87   new_catcher->saved_cleanup_chain = save_cleanups ();
  88
  89   /* Push this new catcher on the top.  */
  90   new_catcher->prev = current_catcher;
  91   current_catcher = new_catcher;
  92   new_catcher->state = CATCHER_CREATED;
  93
  94   return &new_catcher->buf;
  95 }
  96
  97 static void
  98 catcher_pop (void)
  99 {
 100   struct catcher *old_catcher = current_catcher;
 101
 102   current_catcher = old_catcher->prev;
 103
 104   /* Restore the cleanup chain, the error/quit messages, and the uiout
 105      builder, to their original states.  */
 106
 107   restore_cleanups (old_catcher->saved_cleanup_chain);
 108
 109   xfree (old_catcher);
 110 }
 111
 112 /* Catcher state machine.  Returns non-zero if the m/c should be run
 113    again, zero if it should abort.  */
 114
 115 static int
 116 exceptions_state_mc (enum catcher_action action)
 117 {
 118   switch (current_catcher->state)
 119     {
 120     case CATCHER_CREATED:
 121       switch (action)
 122         {
 123         case CATCH_ITER:
 124           /* Allow the code to run the catcher.  */
 125           current_catcher->state = CATCHER_RUNNING;
 126           return 1;
 127         default:
 128           internal_error (__FILE__, __LINE__, _("bad state"));
 129         }
 130     case CATCHER_RUNNING:
 131       switch (action)
 132         {
 133         case CATCH_ITER:
 134           /* No error/quit has occured.  Just clean up.  */
 135           catcher_pop ();
 136           return 0;
 137         case CATCH_ITER_1:
 138           current_catcher->state = CATCHER_RUNNING_1;
 139           return 1;
 140         case CATCH_THROWING:
 141           current_catcher->state = CATCHER_ABORTING;
 142           /* See also throw_exception.  */
 143           return 1;
 144         default:
 145           internal_error (__FILE__, __LINE__, _("bad switch"));
 146         }
 147     case CATCHER_RUNNING_1:
 148       switch (action)
 149         {
 150         case CATCH_ITER:
 151           /* The did a "break" from the inner while loop.  */
 152           catcher_pop ();
 153           return 0;
 154         case CATCH_ITER_1:
 155           current_catcher->state = CATCHER_RUNNING;
 156           return 0;
 157         case CATCH_THROWING:
 158           current_catcher->state = CATCHER_ABORTING;
 159           /* See also throw_exception.  */
 160           return 1;
 161         default:
 162           internal_error (__FILE__, __LINE__, _("bad switch"));
 163         }
 164     case CATCHER_ABORTING:
 165       switch (action)
 166         {
 167         case CATCH_ITER:
 168           {
 169             struct gdb_exception exception = *current_catcher->exception;
 170
 171             if (current_catcher->mask & RETURN_MASK (exception.reason))
 172               {
 173                 /* Exit normally if this catcher can handle this
 174                    exception.  The caller analyses the func return
 175                    values.  */
 176                 catcher_pop ();
 177                 return 0;
 178               }
 179             /* The caller didn't request that the event be caught,
 180                relay the event to the next containing
 181                catch_errors().  */
 182             catcher_pop ();
 183             throw_exception (exception);
 184           }
 185         default:
 186           internal_error (__FILE__, __LINE__, _("bad state"));
 187         }
 188     default:
 189       internal_error (__FILE__, __LINE__, _("bad switch"));
 190     }
 191 }
 192
 193 int
 194 exceptions_state_mc_action_iter (void)
 195 {
 196   return exceptions_state_mc (CATCH_ITER);
 197 }
 198
 199 int
 200 exceptions_state_mc_action_iter_1 (void)
 201 {
 202   return exceptions_state_mc (CATCH_ITER_1);
 203 }
 204
 205 /* Return EXCEPTION to the nearest containing catch_errors().  */
 206
 207 void
 208 throw_exception (struct gdb_exception exception)
 209 {
 210   struct thread_info *tp = NULL;
 211
 212   quit_flag = 0;
 213   immediate_quit = 0;
 214
 215   if (!ptid_equal (inferior_ptid, null_ptid))
 216     tp = find_thread_ptid (inferior_ptid);
 217
 218   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 219      I can think of a reason why that is vital, though).  */
 220   if (tp != NULL)
 221     {
 222       /* Clear queued breakpoint commands.  */
 223       bpstat_clear_actions (tp->control.stop_bpstat);
 224     }
 225
 226   disable_current_display ();
 227   do_cleanups (ALL_CLEANUPS);
 228
 229   /* Jump to the containing catch_errors() call, communicating REASON
 230      to that call via setjmp's return value.  Note that REASON can't
 231      be zero, by definition in defs.h.  */
 232   exceptions_state_mc (CATCH_THROWING);
 233   *current_catcher->exception = exception;
 234   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 235 }
 236
 237 static char *last_message;
 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 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 377 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 378           va_list ap)
 379 {
 380   struct gdb_exception e;
 381   char *new_message;
 382
 383   /* Save the message.  Create the new message before deleting the
 384      old, the new message may include the old message text.  */
 385   new_message = xstrvprintf (fmt, ap);
 386   xfree (last_message);
 387   last_message = new_message;
 388
 389   /* Create the exception.  */
 390   e.reason = reason;
 391   e.error = error;
 392   e.message = last_message;
 393
 394   /* Throw the exception.  */
 395   throw_exception (e);
 396 }
 397
 398 void
 399 throw_verror (enum errors error, const char *fmt, va_list ap)
 400 {
 401   throw_it (RETURN_ERROR, error, fmt, ap);
 402 }
 403
 404 void
 405 throw_vfatal (const char *fmt, va_list ap)
 406 {
 407   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 408 }
 409
 410 void
 411 throw_error (enum errors error, const char *fmt, ...)
 412 {
 413   va_list args;
 414
 415   va_start (args, fmt);
 416   throw_it (RETURN_ERROR, error, fmt, args);
 417   va_end (args);
 418 }
 419
 420 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 421    handler.  If an exception (enum return_reason) is thrown using
 422    throw_exception() than all cleanups installed since
 423    catch_exceptions() was entered are invoked, the (-ve) exception
 424    value is then returned by catch_exceptions.  If FUNC() returns
 425    normally (with a positive or zero return value) then that value is
 426    returned by catch_exceptions().  It is an internal_error() for
 427    FUNC() to return a negative value.
 428
 429    See exceptions.h for further usage details.
 430
 431    Must not be called with immediate_quit in effect (bad things might
 432    happen, say we got a signal in the middle of a memcpy to quit_return).
 433    This is an OK restriction; with very few exceptions immediate_quit can
 434    be replaced by judicious use of QUIT.  */
 435
 436 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 437    error() et al. could maintain a set of flags that indicate the
 438    current state of each of the longjmp buffers.  This would give the
 439    longjmp code the chance to detect a longjmp botch (before it gets
 440    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 441    code also randomly used a SET_TOP_LEVEL macro that directly
 442    initialized the longjmp buffers.  */
 443
 444 int
 445 catch_exceptions (struct ui_out *uiout,
 446                   catch_exceptions_ftype *func,
 447                   void *func_args,
 448                   return_mask mask)
 449 {
 450   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 451 }
 452
 453 int
 454 catch_exceptions_with_msg (struct ui_out *func_uiout,
 455                            catch_exceptions_ftype *func,
 456                            void *func_args,
 457                            char **gdberrmsg,
 458                            return_mask mask)
 459 {
 460   volatile struct gdb_exception exception;
 461   volatile int val = 0;
 462   struct ui_out *saved_uiout;
 463
 464   /* Save and override the global ``struct ui_out'' builder.  */
 465   saved_uiout = current_uiout;
 466   current_uiout = func_uiout;
 467
 468   TRY_CATCH (exception, RETURN_MASK_ALL)
 469     {
 470       val = (*func) (current_uiout, func_args);
 471     }
 472
 473   /* Restore the global builder.  */
 474   current_uiout = saved_uiout;
 475
 476   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 477     {
 478       /* The caller didn't request that the event be caught.
 479          Rethrow.  */
 480       throw_exception (exception);
 481     }
 482
 483   print_any_exception (gdb_stderr, NULL, exception);
 484   gdb_assert (val >= 0);
 485   gdb_assert (exception.reason <= 0);
 486   if (exception.reason < 0)
 487     {
 488       /* If caller wants a copy of the low-level error message, make
 489          one.  This is used in the case of a silent error whereby the
 490          caller may optionally want to issue the message.  */
 491       if (gdberrmsg != NULL)
 492         {
 493           if (exception.message != NULL)
 494             *gdberrmsg = xstrdup (exception.message);
 495           else
 496             *gdberrmsg = NULL;
 497         }
 498       return exception.reason;
 499     }
 500   return val;
 501 }
 502
 503 /* This function is superseded by catch_exceptions().  */
 504
 505 int
 506 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 507               return_mask mask)
 508 {
 509   volatile int val = 0;
 510   volatile struct gdb_exception exception;
 511   struct ui_out *saved_uiout;
 512
 513   /* Save the global ``struct ui_out'' builder.  */
 514   saved_uiout = current_uiout;
 515
 516   TRY_CATCH (exception, RETURN_MASK_ALL)
 517     {
 518       val = func (func_args);
 519     }
 520
 521   /* Restore the global builder.  */
 522   current_uiout = saved_uiout;
 523
 524   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 525     {
 526       /* The caller didn't request that the event be caught.
 527          Rethrow.  */
 528       throw_exception (exception);
 529     }
 530
 531   print_any_exception (gdb_stderr, errstring, exception);
 532   if (exception.reason != 0)
 533     return 0;
 534   return val;
 535 }
 536
 537 int
 538 catch_command_errors (catch_command_errors_ftype * command,
 539                       char *arg, int from_tty, return_mask mask)
 540 {
 541   volatile struct gdb_exception e;
 542
 543   TRY_CATCH (e, mask)
 544     {
 545       command (arg, from_tty);
 546     }
 547   print_any_exception (gdb_stderr, NULL, e);
 548   if (e.reason < 0)
 549     return 0;
 550   return 1;
 551 }