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 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
 108   current_catcher = old_catcher->prev;
 109
 110   /* Restore the cleanup chain, the error/quit messages, and the uiout
 111      builder, to their original states.  */
 112
 113   restore_cleanups (old_catcher->saved_cleanup_chain);
 114
 115   uiout = old_catcher->saved_uiout;
 116
 117   xfree (old_catcher);
 118 }
 119
 120 /* Catcher state machine.  Returns non-zero if the m/c should be run
 121    again, zero if it should abort.  */
 122
 123 static int
 124 exceptions_state_mc (enum catcher_action action)
 125 {
 126   switch (current_catcher->state)
 127     {
 128     case CATCHER_CREATED:
 129       switch (action)
 130         {
 131         case CATCH_ITER:
 132           /* Allow the code to run the catcher.  */
 133           current_catcher->state = CATCHER_RUNNING;
 134           return 1;
 135         default:
 136           internal_error (__FILE__, __LINE__, _("bad state"));
 137         }
 138     case CATCHER_RUNNING:
 139       switch (action)
 140         {
 141         case CATCH_ITER:
 142           /* No error/quit has occured.  Just clean up.  */
 143           catcher_pop ();
 144           return 0;
 145         case CATCH_ITER_1:
 146           current_catcher->state = CATCHER_RUNNING_1;
 147           return 1;
 148         case CATCH_THROWING:
 149           current_catcher->state = CATCHER_ABORTING;
 150           /* See also throw_exception.  */
 151           return 1;
 152         default:
 153           internal_error (__FILE__, __LINE__, _("bad switch"));
 154         }
 155     case CATCHER_RUNNING_1:
 156       switch (action)
 157         {
 158         case CATCH_ITER:
 159           /* The did a "break" from the inner while loop.  */
 160           catcher_pop ();
 161           return 0;
 162         case CATCH_ITER_1:
 163           current_catcher->state = CATCHER_RUNNING;
 164           return 0;
 165         case CATCH_THROWING:
 166           current_catcher->state = CATCHER_ABORTING;
 167           /* See also throw_exception.  */
 168           return 1;
 169         default:
 170           internal_error (__FILE__, __LINE__, _("bad switch"));
 171         }
 172     case CATCHER_ABORTING:
 173       switch (action)
 174         {
 175         case CATCH_ITER:
 176           {
 177             struct gdb_exception exception = *current_catcher->exception;
 178
 179             if (current_catcher->mask & RETURN_MASK (exception.reason))
 180               {
 181                 /* Exit normally if this catcher can handle this
 182                    exception.  The caller analyses the func return
 183                    values.  */
 184                 catcher_pop ();
 185                 return 0;
 186               }
 187             /* The caller didn't request that the event be caught,
 188                relay the event to the next containing
 189                catch_errors().  */
 190             catcher_pop ();
 191             throw_exception (exception);
 192           }
 193         default:
 194           internal_error (__FILE__, __LINE__, _("bad state"));
 195         }
 196     default:
 197       internal_error (__FILE__, __LINE__, _("bad switch"));
 198     }
 199 }
 200
 201 int
 202 exceptions_state_mc_action_iter (void)
 203 {
 204   return exceptions_state_mc (CATCH_ITER);
 205 }
 206
 207 int
 208 exceptions_state_mc_action_iter_1 (void)
 209 {
 210   return exceptions_state_mc (CATCH_ITER_1);
 211 }
 212
 213 /* Return EXCEPTION to the nearest containing catch_errors().  */
 214
 215 void
 216 throw_exception (struct gdb_exception exception)
 217 {
 218   struct thread_info *tp = NULL;
 219
 220   quit_flag = 0;
 221   immediate_quit = 0;
 222
 223   if (!ptid_equal (inferior_ptid, null_ptid))
 224     tp = find_thread_ptid (inferior_ptid);
 225
 226   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 227      I can think of a reason why that is vital, though).  */
 228   if (tp != NULL)
 229     {
 230       /* Clear queued breakpoint commands.  */
 231       bpstat_clear_actions (tp->control.stop_bpstat);
 232     }
 233
 234   disable_current_display ();
 235   do_cleanups (ALL_CLEANUPS);
 236
 237   /* Jump to the containing catch_errors() call, communicating REASON
 238      to that call via setjmp's return value.  Note that REASON can't
 239      be zero, by definition in defs.h.  */
 240   exceptions_state_mc (CATCH_THROWING);
 241   *current_catcher->exception = exception;
 242   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 243 }
 244
 245 static char *last_message;
 246
 247 void
 248 deprecated_throw_reason (enum return_reason reason)
 249 {
 250   struct gdb_exception exception;
 251
 252   memset (&exception, 0, sizeof exception);
 253
 254   exception.reason = reason;
 255   switch (reason)
 256     {
 257     case RETURN_QUIT:
 258       break;
 259     case RETURN_ERROR:
 260       exception.error = GENERIC_ERROR;
 261       break;
 262     default:
 263       internal_error (__FILE__, __LINE__, _("bad switch"));
 264     }
 265
 266   throw_exception (exception);
 267 }
 268
 269 static void
 270 print_flush (void)
 271 {
 272   struct serial *gdb_stdout_serial;
 273
 274   if (deprecated_error_begin_hook)
 275     deprecated_error_begin_hook ();
 276   target_terminal_ours ();
 277
 278   /* We want all output to appear now, before we print the error.  We
 279      have 3 levels of buffering we have to flush (it's possible that
 280      some of these should be changed to flush the lower-level ones
 281      too):  */
 282
 283   /* 1.  The _filtered buffer.  */
 284   wrap_here ("");
 285
 286   /* 2.  The stdio buffer.  */
 287   gdb_flush (gdb_stdout);
 288   gdb_flush (gdb_stderr);
 289
 290   /* 3.  The system-level buffer.  */
 291   gdb_stdout_serial = serial_fdopen (1);
 292   if (gdb_stdout_serial)
 293     {
 294       serial_drain_output (gdb_stdout_serial);
 295       serial_un_fdopen (gdb_stdout_serial);
 296     }
 297
 298   annotate_error_begin ();
 299 }
 300
 301 static void
 302 print_exception (struct ui_file *file, struct gdb_exception e)
 303 {
 304   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 305      as that way the MI's behavior is preserved.  */
 306   const char *start;
 307   const char *end;
 308
 309   for (start = e.message; start != NULL; start = end)
 310     {
 311       end = strchr (start, '\n');
 312       if (end == NULL)
 313         fputs_filtered (start, file);
 314       else
 315         {
 316           end++;
 317           ui_file_write (file, start, end - start);
 318         }
 319     }
 320   fprintf_filtered (file, "\n");
 321
 322   /* Now append the annotation.  */
 323   switch (e.reason)
 324     {
 325     case RETURN_QUIT:
 326       annotate_quit ();
 327       break;
 328     case RETURN_ERROR:
 329       /* Assume that these are all errors.  */
 330       annotate_error ();
 331       break;
 332     default:
 333       internal_error (__FILE__, __LINE__, _("Bad switch."));
 334     }
 335 }
 336
 337 void
 338 exception_print (struct ui_file *file, struct gdb_exception e)
 339 {
 340   if (e.reason < 0 && e.message != NULL)
 341     {
 342       print_flush ();
 343       print_exception (file, e);
 344     }
 345 }
 346
 347 void
 348 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 349                    const char *prefix, ...)
 350 {
 351   if (e.reason < 0 && e.message != NULL)
 352     {
 353       va_list args;
 354
 355       print_flush ();
 356
 357       /* Print the prefix.  */
 358       va_start (args, prefix);
 359       vfprintf_filtered (file, prefix, args);
 360       va_end (args);
 361
 362       print_exception (file, e);
 363     }
 364 }
 365
 366 static void
 367 print_any_exception (struct ui_file *file, const char *prefix,
 368                      struct gdb_exception e)
 369 {
 370   if (e.reason < 0 && e.message != NULL)
 371     {
 372       target_terminal_ours ();
 373       wrap_here ("");           /* Force out any buffered output.  */
 374       gdb_flush (gdb_stdout);
 375       annotate_error_begin ();
 376
 377       /* Print the prefix.  */
 378       if (prefix != NULL && prefix[0] != '\0')
 379         fputs_filtered (prefix, file);
 380       print_exception (file, e);
 381     }
 382 }
 383
 384 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 385 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 386           va_list ap)
 387 {
 388   struct gdb_exception e;
 389   char *new_message;
 390
 391   /* Save the message.  Create the new message before deleting the
 392      old, the new message may include the old message text.  */
 393   new_message = xstrvprintf (fmt, ap);
 394   xfree (last_message);
 395   last_message = new_message;
 396
 397   /* Create the exception.  */
 398   e.reason = reason;
 399   e.error = error;
 400   e.message = last_message;
 401
 402   /* Throw the exception.  */
 403   throw_exception (e);
 404 }
 405
 406 void
 407 throw_verror (enum errors error, const char *fmt, va_list ap)
 408 {
 409   throw_it (RETURN_ERROR, error, fmt, ap);
 410 }
 411
 412 void
 413 throw_vfatal (const char *fmt, va_list ap)
 414 {
 415   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 416 }
 417
 418 void
 419 throw_error (enum errors error, const char *fmt, ...)
 420 {
 421   va_list args;
 422
 423   va_start (args, fmt);
 424   throw_it (RETURN_ERROR, error, fmt, args);
 425   va_end (args);
 426 }
 427
 428 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 429    handler.  If an exception (enum return_reason) is thrown using
 430    throw_exception() than all cleanups installed since
 431    catch_exceptions() was entered are invoked, the (-ve) exception
 432    value is then returned by catch_exceptions.  If FUNC() returns
 433    normally (with a positive or zero return value) then that value is
 434    returned by catch_exceptions().  It is an internal_error() for
 435    FUNC() to return a negative value.
 436
 437    See exceptions.h for further usage details.
 438
 439    Must not be called with immediate_quit in effect (bad things might
 440    happen, say we got a signal in the middle of a memcpy to quit_return).
 441    This is an OK restriction; with very few exceptions immediate_quit can
 442    be replaced by judicious use of QUIT.  */
 443
 444 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 445    error() et al. could maintain a set of flags that indicate the the
 446    current state of each of the longjmp buffers.  This would give the
 447    longjmp code the chance to detect a longjmp botch (before it gets
 448    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 449    code also randomly used a SET_TOP_LEVEL macro that directly
 450    initialized the longjmp buffers.  */
 451
 452 int
 453 catch_exceptions (struct ui_out *uiout,
 454                   catch_exceptions_ftype *func,
 455                   void *func_args,
 456                   return_mask mask)
 457 {
 458   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 459 }
 460
 461 struct gdb_exception
 462 catch_exception (struct ui_out *uiout,
 463                  catch_exception_ftype *func,
 464                  void *func_args,
 465                  return_mask mask)
 466 {
 467   volatile struct gdb_exception exception;
 468
 469   TRY_CATCH (exception, mask)
 470     {
 471       (*func) (uiout, func_args);
 472     }
 473   return exception;
 474 }
 475
 476 int
 477 catch_exceptions_with_msg (struct ui_out *uiout,
 478                            catch_exceptions_ftype *func,
 479                            void *func_args,
 480                            char **gdberrmsg,
 481                            return_mask mask)
 482 {
 483   volatile struct gdb_exception exception;
 484   volatile int val = 0;
 485
 486   TRY_CATCH (exception, mask)
 487     {
 488       val = (*func) (uiout, func_args);
 489     }
 490   print_any_exception (gdb_stderr, NULL, exception);
 491   gdb_assert (val >= 0);
 492   gdb_assert (exception.reason <= 0);
 493   if (exception.reason < 0)
 494     {
 495       /* If caller wants a copy of the low-level error message, make
 496          one.  This is used in the case of a silent error whereby the
 497          caller may optionally want to issue the message.  */
 498       if (gdberrmsg != NULL)
 499         {
 500           if (exception.message != NULL)
 501             *gdberrmsg = xstrdup (exception.message);
 502           else
 503             *gdberrmsg = NULL;
 504         }
 505       return exception.reason;
 506     }
 507   return val;
 508 }
 509
 510 /* This function is superseded by catch_exceptions().  */
 511
 512 int
 513 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 514               return_mask mask)
 515 {
 516   volatile int val = 0;
 517   volatile struct gdb_exception exception;
 518
 519   TRY_CATCH (exception, mask)
 520     {
 521       val = func (func_args);
 522     }
 523   print_any_exception (gdb_stderr, errstring, exception);
 524   if (exception.reason != 0)
 525     return 0;
 526   return val;
 527 }
 528
 529 int
 530 catch_command_errors (catch_command_errors_ftype * command,
 531                       char *arg, int from_tty, return_mask mask)
 532 {
 533   volatile struct gdb_exception e;
 534
 535   TRY_CATCH (e, mask)
 536     {
 537       command (arg, from_tty);
 538     }
 539   print_any_exception (gdb_stderr, NULL, e);
 540   if (e.reason < 0)
 541     return 0;
 542   return 1;
 543 }