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   quit_flag = 0;
 211   immediate_quit = 0;
 212
 213   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 214      I can think of a reason why that is vital, though).  */
 215   bpstat_clear_actions ();
 216
 217   do_cleanups (ALL_CLEANUPS);
 218
 219   /* Jump to the containing catch_errors() call, communicating REASON
 220      to that call via setjmp's return value.  Note that REASON can't
 221      be zero, by definition in defs.h.  */
 222   exceptions_state_mc (CATCH_THROWING);
 223   *current_catcher->exception = exception;
 224   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 225 }
 226
 227 static char *last_message;
 228
 229 void
 230 deprecated_throw_reason (enum return_reason reason)
 231 {
 232   struct gdb_exception exception;
 233
 234   memset (&exception, 0, sizeof exception);
 235
 236   exception.reason = reason;
 237   switch (reason)
 238     {
 239     case RETURN_QUIT:
 240       break;
 241     case RETURN_ERROR:
 242       exception.error = GENERIC_ERROR;
 243       break;
 244     default:
 245       internal_error (__FILE__, __LINE__, _("bad switch"));
 246     }
 247
 248   throw_exception (exception);
 249 }
 250
 251 static void
 252 print_flush (void)
 253 {
 254   struct serial *gdb_stdout_serial;
 255
 256   if (deprecated_error_begin_hook)
 257     deprecated_error_begin_hook ();
 258   target_terminal_ours ();
 259
 260   /* We want all output to appear now, before we print the error.  We
 261      have 3 levels of buffering we have to flush (it's possible that
 262      some of these should be changed to flush the lower-level ones
 263      too):  */
 264
 265   /* 1.  The _filtered buffer.  */
 266   wrap_here ("");
 267
 268   /* 2.  The stdio buffer.  */
 269   gdb_flush (gdb_stdout);
 270   gdb_flush (gdb_stderr);
 271
 272   /* 3.  The system-level buffer.  */
 273   gdb_stdout_serial = serial_fdopen (1);
 274   if (gdb_stdout_serial)
 275     {
 276       serial_drain_output (gdb_stdout_serial);
 277       serial_un_fdopen (gdb_stdout_serial);
 278     }
 279
 280   annotate_error_begin ();
 281 }
 282
 283 static void
 284 print_exception (struct ui_file *file, struct gdb_exception e)
 285 {
 286   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 287      as that way the MI's behavior is preserved.  */
 288   const char *start;
 289   const char *end;
 290
 291   for (start = e.message; start != NULL; start = end)
 292     {
 293       end = strchr (start, '\n');
 294       if (end == NULL)
 295         fputs_filtered (start, file);
 296       else
 297         {
 298           end++;
 299           ui_file_write (file, start, end - start);
 300         }
 301     }
 302   fprintf_filtered (file, "\n");
 303
 304   /* Now append the annotation.  */
 305   switch (e.reason)
 306     {
 307     case RETURN_QUIT:
 308       annotate_quit ();
 309       break;
 310     case RETURN_ERROR:
 311       /* Assume that these are all errors.  */
 312       annotate_error ();
 313       break;
 314     default:
 315       internal_error (__FILE__, __LINE__, _("Bad switch."));
 316     }
 317 }
 318
 319 void
 320 exception_print (struct ui_file *file, struct gdb_exception e)
 321 {
 322   if (e.reason < 0 && e.message != NULL)
 323     {
 324       print_flush ();
 325       print_exception (file, e);
 326     }
 327 }
 328
 329 void
 330 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 331                    const char *prefix, ...)
 332 {
 333   if (e.reason < 0 && e.message != NULL)
 334     {
 335       va_list args;
 336
 337       print_flush ();
 338
 339       /* Print the prefix.  */
 340       va_start (args, prefix);
 341       vfprintf_filtered (file, prefix, args);
 342       va_end (args);
 343
 344       print_exception (file, e);
 345     }
 346 }
 347
 348 static void
 349 print_any_exception (struct ui_file *file, const char *prefix,
 350                      struct gdb_exception e)
 351 {
 352   if (e.reason < 0 && e.message != NULL)
 353     {
 354       target_terminal_ours ();
 355       wrap_here ("");           /* Force out any buffered output.  */
 356       gdb_flush (gdb_stdout);
 357       annotate_error_begin ();
 358
 359       /* Print the prefix.  */
 360       if (prefix != NULL && prefix[0] != '\0')
 361         fputs_filtered (prefix, file);
 362       print_exception (file, e);
 363     }
 364 }
 365
 366 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 367 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 368           va_list ap)
 369 {
 370   struct gdb_exception e;
 371   char *new_message;
 372
 373   /* Save the message.  Create the new message before deleting the
 374      old, the new message may include the old message text.  */
 375   new_message = xstrvprintf (fmt, ap);
 376   xfree (last_message);
 377   last_message = new_message;
 378
 379   /* Create the exception.  */
 380   e.reason = reason;
 381   e.error = error;
 382   e.message = last_message;
 383
 384   /* Throw the exception.  */
 385   throw_exception (e);
 386 }
 387
 388 void
 389 throw_verror (enum errors error, const char *fmt, va_list ap)
 390 {
 391   throw_it (RETURN_ERROR, error, fmt, ap);
 392 }
 393
 394 void
 395 throw_vfatal (const char *fmt, va_list ap)
 396 {
 397   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 398 }
 399
 400 void
 401 throw_error (enum errors error, const char *fmt, ...)
 402 {
 403   va_list args;
 404
 405   va_start (args, fmt);
 406   throw_it (RETURN_ERROR, error, fmt, args);
 407   va_end (args);
 408 }
 409
 410 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 411    handler.  If an exception (enum return_reason) is thrown using
 412    throw_exception() than all cleanups installed since
 413    catch_exceptions() was entered are invoked, the (-ve) exception
 414    value is then returned by catch_exceptions.  If FUNC() returns
 415    normally (with a positive or zero return value) then that value is
 416    returned by catch_exceptions().  It is an internal_error() for
 417    FUNC() to return a negative value.
 418
 419    See exceptions.h for further usage details.
 420
 421    Must not be called with immediate_quit in effect (bad things might
 422    happen, say we got a signal in the middle of a memcpy to quit_return).
 423    This is an OK restriction; with very few exceptions immediate_quit can
 424    be replaced by judicious use of QUIT.  */
 425
 426 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 427    error() et al. could maintain a set of flags that indicate the
 428    current state of each of the longjmp buffers.  This would give the
 429    longjmp code the chance to detect a longjmp botch (before it gets
 430    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 431    code also randomly used a SET_TOP_LEVEL macro that directly
 432    initialized the longjmp buffers.  */
 433
 434 int
 435 catch_exceptions (struct ui_out *uiout,
 436                   catch_exceptions_ftype *func,
 437                   void *func_args,
 438                   return_mask mask)
 439 {
 440   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 441 }
 442
 443 int
 444 catch_exceptions_with_msg (struct ui_out *func_uiout,
 445                            catch_exceptions_ftype *func,
 446                            void *func_args,
 447                            char **gdberrmsg,
 448                            return_mask mask)
 449 {
 450   volatile struct gdb_exception exception;
 451   volatile int val = 0;
 452   struct ui_out *saved_uiout;
 453
 454   /* Save and override the global ``struct ui_out'' builder.  */
 455   saved_uiout = current_uiout;
 456   current_uiout = func_uiout;
 457
 458   TRY_CATCH (exception, RETURN_MASK_ALL)
 459     {
 460       val = (*func) (current_uiout, func_args);
 461     }
 462
 463   /* Restore the global builder.  */
 464   current_uiout = saved_uiout;
 465
 466   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 467     {
 468       /* The caller didn't request that the event be caught.
 469          Rethrow.  */
 470       throw_exception (exception);
 471     }
 472
 473   print_any_exception (gdb_stderr, NULL, exception);
 474   gdb_assert (val >= 0);
 475   gdb_assert (exception.reason <= 0);
 476   if (exception.reason < 0)
 477     {
 478       /* If caller wants a copy of the low-level error message, make
 479          one.  This is used in the case of a silent error whereby the
 480          caller may optionally want to issue the message.  */
 481       if (gdberrmsg != NULL)
 482         {
 483           if (exception.message != NULL)
 484             *gdberrmsg = xstrdup (exception.message);
 485           else
 486             *gdberrmsg = NULL;
 487         }
 488       return exception.reason;
 489     }
 490   return val;
 491 }
 492
 493 /* This function is superseded by catch_exceptions().  */
 494
 495 int
 496 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 497               return_mask mask)
 498 {
 499   volatile int val = 0;
 500   volatile struct gdb_exception exception;
 501   struct ui_out *saved_uiout;
 502
 503   /* Save the global ``struct ui_out'' builder.  */
 504   saved_uiout = current_uiout;
 505
 506   TRY_CATCH (exception, RETURN_MASK_ALL)
 507     {
 508       val = func (func_args);
 509     }
 510
 511   /* Restore the global builder.  */
 512   current_uiout = saved_uiout;
 513
 514   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 515     {
 516       /* The caller didn't request that the event be caught.
 517          Rethrow.  */
 518       throw_exception (exception);
 519     }
 520
 521   print_any_exception (gdb_stderr, errstring, exception);
 522   if (exception.reason != 0)
 523     return 0;
 524   return val;
 525 }
 526
 527 int
 528 catch_command_errors (catch_command_errors_ftype * command,
 529                       char *arg, int from_tty, return_mask mask)
 530 {
 531   volatile struct gdb_exception e;
 532
 533   TRY_CATCH (e, mask)
 534     {
 535       command (arg, from_tty);
 536     }
 537   print_any_exception (gdb_stderr, NULL, e);
 538   if (e.reason < 0)
 539     return 0;
 540   return 1;
 541 }