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 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     bpstat_clear_actions (tp->stop_bpstat);     /* Clear queued breakpoint commands */
 230
 231   disable_current_display ();
 232   do_cleanups (ALL_CLEANUPS);
 233
 234   /* Jump to the containing catch_errors() call, communicating REASON
 235      to that call via setjmp's return value.  Note that REASON can't
 236      be zero, by definition in defs.h. */
 237   exceptions_state_mc (CATCH_THROWING);
 238   *current_catcher->exception = exception;
 239   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 240 }
 241
 242 static char *last_message;
 243
 244 void
 245 deprecated_throw_reason (enum return_reason reason)
 246 {
 247   struct gdb_exception exception;
 248
 249   memset (&exception, 0, sizeof exception);
 250
 251   exception.reason = reason;
 252   switch (reason)
 253     {
 254     case RETURN_QUIT:
 255       break;
 256     case RETURN_ERROR:
 257       exception.error = GENERIC_ERROR;
 258       break;
 259     default:
 260       internal_error (__FILE__, __LINE__, _("bad switch"));
 261     }
 262
 263   throw_exception (exception);
 264 }
 265
 266 static void
 267 print_flush (void)
 268 {
 269   struct serial *gdb_stdout_serial;
 270
 271   if (deprecated_error_begin_hook)
 272     deprecated_error_begin_hook ();
 273   target_terminal_ours ();
 274
 275   /* We want all output to appear now, before we print the error.  We
 276      have 3 levels of buffering we have to flush (it's possible that
 277      some of these should be changed to flush the lower-level ones
 278      too):  */
 279
 280   /* 1.  The _filtered buffer.  */
 281   wrap_here ("");
 282
 283   /* 2.  The stdio buffer.  */
 284   gdb_flush (gdb_stdout);
 285   gdb_flush (gdb_stderr);
 286
 287   /* 3.  The system-level buffer.  */
 288   gdb_stdout_serial = serial_fdopen (1);
 289   if (gdb_stdout_serial)
 290     {
 291       serial_drain_output (gdb_stdout_serial);
 292       serial_un_fdopen (gdb_stdout_serial);
 293     }
 294
 295   annotate_error_begin ();
 296 }
 297
 298 static void
 299 print_exception (struct ui_file *file, struct gdb_exception e)
 300 {
 301   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 302      as that way the MI's behavior is preserved.  */
 303   const char *start;
 304   const char *end;
 305
 306   for (start = e.message; start != NULL; start = end)
 307     {
 308       end = strchr (start, '\n');
 309       if (end == NULL)
 310         fputs_filtered (start, file);
 311       else
 312         {
 313           end++;
 314           ui_file_write (file, start, end - start);
 315         }
 316     }
 317   fprintf_filtered (file, "\n");
 318
 319   /* Now append the annotation.  */
 320   switch (e.reason)
 321     {
 322     case RETURN_QUIT:
 323       annotate_quit ();
 324       break;
 325     case RETURN_ERROR:
 326       /* Assume that these are all errors.  */
 327       annotate_error ();
 328       break;
 329     default:
 330       internal_error (__FILE__, __LINE__, _("Bad switch."));
 331     }
 332 }
 333
 334 void
 335 exception_print (struct ui_file *file, struct gdb_exception e)
 336 {
 337   if (e.reason < 0 && e.message != NULL)
 338     {
 339       print_flush ();
 340       print_exception (file, e);
 341     }
 342 }
 343
 344 void
 345 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 346                    const char *prefix, ...)
 347 {
 348   if (e.reason < 0 && e.message != NULL)
 349     {
 350       va_list args;
 351
 352       print_flush ();
 353
 354       /* Print the prefix.  */
 355       va_start (args, prefix);
 356       vfprintf_filtered (file, prefix, args);
 357       va_end (args);
 358
 359       print_exception (file, e);
 360     }
 361 }
 362
 363 static void
 364 print_any_exception (struct ui_file *file, const char *prefix,
 365                      struct gdb_exception e)
 366 {
 367   if (e.reason < 0 && e.message != NULL)
 368     {
 369       target_terminal_ours ();
 370       wrap_here ("");           /* Force out any buffered output */
 371       gdb_flush (gdb_stdout);
 372       annotate_error_begin ();
 373
 374       /* Print the prefix.  */
 375       if (prefix != NULL && prefix[0] != '\0')
 376         fputs_filtered (prefix, file);
 377       print_exception (file, e);
 378     }
 379 }
 380
 381 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 382 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 383           va_list ap)
 384 {
 385   struct gdb_exception e;
 386   char *new_message;
 387
 388   /* Save the message.  Create the new message before deleting the
 389      old, the new message may include the old message text.  */
 390   new_message = xstrvprintf (fmt, ap);
 391   xfree (last_message);
 392   last_message = new_message;
 393
 394   /* Create the exception.  */
 395   e.reason = reason;
 396   e.error = error;
 397   e.message = last_message;
 398
 399   /* Throw the exception.  */
 400   throw_exception (e);
 401 }
 402
 403 void
 404 throw_verror (enum errors error, const char *fmt, va_list ap)
 405 {
 406   throw_it (RETURN_ERROR, error, fmt, ap);
 407 }
 408
 409 void
 410 throw_vfatal (const char *fmt, va_list ap)
 411 {
 412   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 413 }
 414
 415 void
 416 throw_error (enum errors error, const char *fmt, ...)
 417 {
 418   va_list args;
 419
 420   va_start (args, fmt);
 421   throw_it (RETURN_ERROR, error, fmt, args);
 422   va_end (args);
 423 }
 424
 425 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 426    handler.  If an exception (enum return_reason) is thrown using
 427    throw_exception() than all cleanups installed since
 428    catch_exceptions() was entered are invoked, the (-ve) exception
 429    value is then returned by catch_exceptions.  If FUNC() returns
 430    normally (with a positive or zero return value) then that value is
 431    returned by catch_exceptions().  It is an internal_error() for
 432    FUNC() to return a negative value.
 433
 434    See exceptions.h for further usage details.
 435
 436    Must not be called with immediate_quit in effect (bad things might
 437    happen, say we got a signal in the middle of a memcpy to quit_return).
 438    This is an OK restriction; with very few exceptions immediate_quit can
 439    be replaced by judicious use of QUIT.  */
 440
 441 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 442    error() et.al. could maintain a set of flags that indicate the the
 443    current state of each of the longjmp buffers.  This would give the
 444    longjmp code the chance to detect a longjmp botch (before it gets
 445    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 446    code also randomly used a SET_TOP_LEVEL macro that directly
 447    initialize the longjmp buffers. */
 448
 449 int
 450 catch_exceptions (struct ui_out *uiout,
 451                   catch_exceptions_ftype *func,
 452                   void *func_args,
 453                   return_mask mask)
 454 {
 455   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 456 }
 457
 458 struct gdb_exception
 459 catch_exception (struct ui_out *uiout,
 460                  catch_exception_ftype *func,
 461                  void *func_args,
 462                  return_mask mask)
 463 {
 464   volatile struct gdb_exception exception;
 465
 466   TRY_CATCH (exception, mask)
 467     {
 468       (*func) (uiout, func_args);
 469     }
 470   return exception;
 471 }
 472
 473 int
 474 catch_exceptions_with_msg (struct ui_out *uiout,
 475                            catch_exceptions_ftype *func,
 476                            void *func_args,
 477                            char **gdberrmsg,
 478                            return_mask mask)
 479 {
 480   volatile struct gdb_exception exception;
 481   volatile int val = 0;
 482
 483   TRY_CATCH (exception, mask)
 484     {
 485       val = (*func) (uiout, func_args);
 486     }
 487   print_any_exception (gdb_stderr, NULL, exception);
 488   gdb_assert (val >= 0);
 489   gdb_assert (exception.reason <= 0);
 490   if (exception.reason < 0)
 491     {
 492       /* If caller wants a copy of the low-level error message, make
 493          one.  This is used in the case of a silent error whereby the
 494          caller may optionally want to issue the message.  */
 495       if (gdberrmsg != NULL)
 496         {
 497           if (exception.message != NULL)
 498             *gdberrmsg = xstrdup (exception.message);
 499           else
 500             *gdberrmsg = NULL;
 501         }
 502       return exception.reason;
 503     }
 504   return val;
 505 }
 506
 507 /* This function is superseded by catch_exceptions().  */
 508
 509 int
 510 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 511               return_mask mask)
 512 {
 513   volatile int val = 0;
 514   volatile struct gdb_exception exception;
 515
 516   TRY_CATCH (exception, mask)
 517     {
 518       val = func (func_args);
 519     }
 520   print_any_exception (gdb_stderr, errstring, exception);
 521   if (exception.reason != 0)
 522     return 0;
 523   return val;
 524 }
 525
 526 int
 527 catch_command_errors (catch_command_errors_ftype * command,
 528                       char *arg, int from_tty, return_mask mask)
 529 {
 530   volatile struct gdb_exception e;
 531
 532   TRY_CATCH (e, mask)
 533     {
 534       command (arg, from_tty);
 535     }
 536   print_any_exception (gdb_stderr, NULL, e);
 537   if (e.reason < 0)
 538     return 0;
 539   return 1;
 540 }