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 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 ui_out *saved_uiout;
  64   struct cleanup *saved_cleanup_chain;
  65   /* Back link.  */
  66   struct catcher *prev;
  67 };
  68
  69 /* Where to go for throw_exception().  */
  70 static struct catcher *current_catcher;
  71
  72 EXCEPTIONS_SIGJMP_BUF *
  73 exceptions_state_mc_init (struct ui_out *func_uiout,
  74                           volatile struct gdb_exception *exception,
  75                           return_mask mask)
  76 {
  77   struct catcher *new_catcher = XZALLOC (struct catcher);
  78
  79   /* Start with no exception, save it's address.  */
  80   exception->reason = 0;
  81   exception->error = GDB_NO_ERROR;
  82   exception->message = NULL;
  83   new_catcher->exception = exception;
  84
  85   new_catcher->mask = mask;
  86
  87   /* Override the global ``struct ui_out'' builder.  */
  88   new_catcher->saved_uiout = uiout;
  89   uiout = func_uiout;
  90
  91   /* Prevent error/quit during FUNC from calling cleanups established
  92      prior to here. */
  93   new_catcher->saved_cleanup_chain = save_cleanups ();
  94
  95   /* Push this new catcher on the top.  */
  96   new_catcher->prev = current_catcher;
  97   current_catcher = new_catcher;
  98   new_catcher->state = CATCHER_CREATED;
  99
 100   return &new_catcher->buf;
 101 }
 102
 103 static void
 104 catcher_pop (void)
 105 {
 106   struct catcher *old_catcher = current_catcher;
 107   current_catcher = old_catcher->prev;
 108
 109   /* Restore the cleanup chain, the error/quit messages, and the uiout
 110      builder, to their original states. */
 111
 112   restore_cleanups (old_catcher->saved_cleanup_chain);
 113
 114   uiout = old_catcher->saved_uiout;
 115
 116   xfree (old_catcher);
 117 }
 118
 119 /* Catcher state machine.  Returns non-zero if the m/c should be run
 120    again, zero if it should abort.  */
 121
 122 static int
 123 exceptions_state_mc (enum catcher_action action)
 124 {
 125   switch (current_catcher->state)
 126     {
 127     case CATCHER_CREATED:
 128       switch (action)
 129         {
 130         case CATCH_ITER:
 131           /* Allow the code to run the catcher.  */
 132           current_catcher->state = CATCHER_RUNNING;
 133           return 1;
 134         default:
 135           internal_error (__FILE__, __LINE__, _("bad state"));
 136         }
 137     case CATCHER_RUNNING:
 138       switch (action)
 139         {
 140         case CATCH_ITER:
 141           /* No error/quit has occured.  Just clean up.  */
 142           catcher_pop ();
 143           return 0;
 144         case CATCH_ITER_1:
 145           current_catcher->state = CATCHER_RUNNING_1;
 146           return 1;
 147         case CATCH_THROWING:
 148           current_catcher->state = CATCHER_ABORTING;
 149           /* See also throw_exception.  */
 150           return 1;
 151         default:
 152           internal_error (__FILE__, __LINE__, _("bad switch"));
 153         }
 154     case CATCHER_RUNNING_1:
 155       switch (action)
 156         {
 157         case CATCH_ITER:
 158           /* The did a "break" from the inner while loop.  */
 159           catcher_pop ();
 160           return 0;
 161         case CATCH_ITER_1:
 162           current_catcher->state = CATCHER_RUNNING;
 163           return 0;
 164         case CATCH_THROWING:
 165           current_catcher->state = CATCHER_ABORTING;
 166           /* See also throw_exception.  */
 167           return 1;
 168         default:
 169           internal_error (__FILE__, __LINE__, _("bad switch"));
 170         }
 171     case CATCHER_ABORTING:
 172       switch (action)
 173         {
 174         case CATCH_ITER:
 175           {
 176             struct gdb_exception exception = *current_catcher->exception;
 177             if (current_catcher->mask & RETURN_MASK (exception.reason))
 178               {
 179                 /* Exit normally if this catcher can handle this
 180                    exception.  The caller analyses the func return
 181                    values.  */
 182                 catcher_pop ();
 183                 return 0;
 184               }
 185             /* The caller didn't request that the event be caught,
 186                relay the event to the next containing
 187                catch_errors(). */
 188             catcher_pop ();
 189             throw_exception (exception);
 190           }
 191         default:
 192           internal_error (__FILE__, __LINE__, _("bad state"));
 193         }
 194     default:
 195       internal_error (__FILE__, __LINE__, _("bad switch"));
 196     }
 197 }
 198
 199 int
 200 exceptions_state_mc_action_iter (void)
 201 {
 202   return exceptions_state_mc (CATCH_ITER);
 203 }
 204
 205 int
 206 exceptions_state_mc_action_iter_1 (void)
 207 {
 208   return exceptions_state_mc (CATCH_ITER_1);
 209 }
 210
 211 /* Return EXCEPTION to the nearest containing catch_errors().  */
 212
 213 NORETURN void
 214 throw_exception (struct gdb_exception exception)
 215 {
 216   struct thread_info *tp = NULL;
 217
 218   quit_flag = 0;
 219   immediate_quit = 0;
 220
 221   if (!ptid_equal (inferior_ptid, null_ptid))
 222     tp = find_thread_pid (inferior_ptid);
 223
 224   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 225      I can think of a reason why that is vital, though).  */
 226   if (tp != NULL)
 227     bpstat_clear_actions (tp->stop_bpstat);     /* Clear queued breakpoint commands */
 228
 229   disable_current_display ();
 230   do_cleanups (ALL_CLEANUPS);
 231
 232   /* Jump to the containing catch_errors() call, communicating REASON
 233      to that call via setjmp's return value.  Note that REASON can't
 234      be zero, by definition in defs.h. */
 235   exceptions_state_mc (CATCH_THROWING);
 236   *current_catcher->exception = exception;
 237   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 238 }
 239
 240 static char *last_message;
 241
 242 NORETURN void
 243 deprecated_throw_reason (enum return_reason reason)
 244 {
 245   struct gdb_exception exception;
 246   memset (&exception, 0, sizeof exception);
 247
 248   exception.reason = reason;
 249   switch (reason)
 250     {
 251     case RETURN_QUIT:
 252       break;
 253     case RETURN_ERROR:
 254       exception.error = GENERIC_ERROR;
 255       break;
 256     default:
 257       internal_error (__FILE__, __LINE__, _("bad switch"));
 258     }
 259
 260   throw_exception (exception);
 261 }
 262
 263 static void
 264 print_flush (void)
 265 {
 266   struct serial *gdb_stdout_serial;
 267
 268   if (deprecated_error_begin_hook)
 269     deprecated_error_begin_hook ();
 270   target_terminal_ours ();
 271
 272   /* We want all output to appear now, before we print the error.  We
 273      have 3 levels of buffering we have to flush (it's possible that
 274      some of these should be changed to flush the lower-level ones
 275      too):  */
 276
 277   /* 1.  The _filtered buffer.  */
 278   wrap_here ("");
 279
 280   /* 2.  The stdio buffer.  */
 281   gdb_flush (gdb_stdout);
 282   gdb_flush (gdb_stderr);
 283
 284   /* 3.  The system-level buffer.  */
 285   gdb_stdout_serial = serial_fdopen (1);
 286   if (gdb_stdout_serial)
 287     {
 288       serial_drain_output (gdb_stdout_serial);
 289       serial_un_fdopen (gdb_stdout_serial);
 290     }
 291
 292   annotate_error_begin ();
 293 }
 294
 295 static void
 296 print_exception (struct ui_file *file, struct gdb_exception e)
 297 {
 298   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 299      as that way the MI's behavior is preserved.  */
 300   const char *start;
 301   const char *end;
 302   for (start = e.message; start != NULL; start = end)
 303     {
 304       end = strchr (start, '\n');
 305       if (end == NULL)
 306         fputs_filtered (start, file);
 307       else
 308         {
 309           end++;
 310           ui_file_write (file, start, end - start);
 311         }
 312     }
 313   fprintf_filtered (file, "\n");
 314
 315   /* Now append the annotation.  */
 316   switch (e.reason)
 317     {
 318     case RETURN_QUIT:
 319       annotate_quit ();
 320       break;
 321     case RETURN_ERROR:
 322       /* Assume that these are all errors.  */
 323       annotate_error ();
 324       break;
 325     default:
 326       internal_error (__FILE__, __LINE__, _("Bad switch."));
 327     }
 328 }
 329
 330 void
 331 exception_print (struct ui_file *file, struct gdb_exception e)
 332 {
 333   if (e.reason < 0 && e.message != NULL)
 334     {
 335       print_flush ();
 336       print_exception (file, e);
 337     }
 338 }
 339
 340 void
 341 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 342                    const char *prefix, ...)
 343 {
 344   if (e.reason < 0 && e.message != NULL)
 345     {
 346       va_list args;
 347
 348       print_flush ();
 349
 350       /* Print the prefix.  */
 351       va_start (args, prefix);
 352       vfprintf_filtered (file, prefix, args);
 353       va_end (args);
 354
 355       print_exception (file, e);
 356     }
 357 }
 358
 359 static void
 360 print_any_exception (struct ui_file *file, const char *prefix,
 361                      struct gdb_exception e)
 362 {
 363   if (e.reason < 0 && e.message != NULL)
 364     {
 365       target_terminal_ours ();
 366       wrap_here ("");           /* Force out any buffered output */
 367       gdb_flush (gdb_stdout);
 368       annotate_error_begin ();
 369
 370       /* Print the prefix.  */
 371       if (prefix != NULL && prefix[0] != '\0')
 372         fputs_filtered (prefix, file);
 373       print_exception (file, e);
 374     }
 375 }
 376
 377 NORETURN static void ATTR_NORETURN ATTR_FORMAT (printf, 3, 0)
 378 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 379           va_list ap)
 380 {
 381   struct gdb_exception e;
 382   char *new_message;
 383
 384   /* Save the message.  Create the new message before deleting the
 385      old, the new message may include the old message text.  */
 386   new_message = xstrvprintf (fmt, ap);
 387   xfree (last_message);
 388   last_message = new_message;
 389
 390   /* Create the exception.  */
 391   e.reason = reason;
 392   e.error = error;
 393   e.message = last_message;
 394
 395   /* Throw the exception.  */
 396   throw_exception (e);
 397 }
 398
 399 NORETURN void
 400 throw_verror (enum errors error, const char *fmt, va_list ap)
 401 {
 402   throw_it (RETURN_ERROR, error, fmt, ap);
 403 }
 404
 405 NORETURN void
 406 throw_vfatal (const char *fmt, va_list ap)
 407 {
 408   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 409 }
 410
 411 NORETURN void
 412 throw_error (enum errors error, const char *fmt, ...)
 413 {
 414   va_list args;
 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 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    initialize 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 struct gdb_exception
 454 catch_exception (struct ui_out *uiout,
 455                  catch_exception_ftype *func,
 456                  void *func_args,
 457                  return_mask mask)
 458 {
 459   volatile struct gdb_exception exception;
 460   TRY_CATCH (exception, mask)
 461     {
 462       (*func) (uiout, func_args);
 463     }
 464   return exception;
 465 }
 466
 467 int
 468 catch_exceptions_with_msg (struct ui_out *uiout,
 469                            catch_exceptions_ftype *func,
 470                            void *func_args,
 471                            char **gdberrmsg,
 472                            return_mask mask)
 473 {
 474   volatile struct gdb_exception exception;
 475   volatile int val = 0;
 476   TRY_CATCH (exception, mask)
 477     {
 478       val = (*func) (uiout, func_args);
 479     }
 480   print_any_exception (gdb_stderr, NULL, exception);
 481   gdb_assert (val >= 0);
 482   gdb_assert (exception.reason <= 0);
 483   if (exception.reason < 0)
 484     {
 485       /* If caller wants a copy of the low-level error message, make
 486          one.  This is used in the case of a silent error whereby the
 487          caller may optionally want to issue the message.  */
 488       if (gdberrmsg != NULL)
 489         {
 490           if (exception.message != NULL)
 491             *gdberrmsg = xstrdup (exception.message);
 492           else
 493             *gdberrmsg = NULL;
 494         }
 495       return exception.reason;
 496     }
 497   return val;
 498 }
 499
 500 /* This function is superseded by catch_exceptions().  */
 501
 502 int
 503 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 504               return_mask mask)
 505 {
 506   volatile int val = 0;
 507   volatile struct gdb_exception exception;
 508   TRY_CATCH (exception, mask)
 509     {
 510       val = func (func_args);
 511     }
 512   print_any_exception (gdb_stderr, errstring, exception);
 513   if (exception.reason != 0)
 514     return 0;
 515   return val;
 516 }
 517
 518 int
 519 catch_command_errors (catch_command_errors_ftype * command,
 520                       char *arg, int from_tty, return_mask mask)
 521 {
 522   volatile struct gdb_exception e;
 523   TRY_CATCH (e, mask)
 524     {
 525       command (arg, from_tty);
 526     }
 527   print_any_exception (gdb_stderr, NULL, e);
 528   if (e.reason < 0)
 529     return 0;
 530   return 1;
 531 }