gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2014 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "exceptions.h"
  22 #include "breakpoint.h"
  23 #include "target.h"
  24 #include "inferior.h"
  25 #include "annotate.h"
  26 #include "ui-out.h"
  27 #include "serial.h"
  28 #include "gdbthread.h"
  29
  30 const struct gdb_exception exception_none = { 0, GDB_NO_ERROR, NULL };
  31
  32 /* Possible catcher states.  */
  33 enum catcher_state {
  34   /* Initial state, a new catcher has just been created.  */
  35   CATCHER_CREATED,
  36   /* The catch code is running.  */
  37   CATCHER_RUNNING,
  38   CATCHER_RUNNING_1,
  39   /* The catch code threw an exception.  */
  40   CATCHER_ABORTING
  41 };
  42
  43 /* Possible catcher actions.  */
  44 enum catcher_action {
  45   CATCH_ITER,
  46   CATCH_ITER_1,
  47   CATCH_THROWING
  48 };
  49
  50 struct catcher
  51 {
  52   enum catcher_state state;
  53   /* Jump buffer pointing back at the exception handler.  */
  54   EXCEPTIONS_SIGJMP_BUF buf;
  55   /* Status buffer belonging to the exception handler.  */
  56   volatile struct gdb_exception *exception;
  57   /* Saved/current state.  */
  58   int mask;
  59   struct cleanup *saved_cleanup_chain;
  60   /* Back link.  */
  61   struct catcher *prev;
  62 };
  63
  64 /* Where to go for throw_exception().  */
  65 static struct catcher *current_catcher;
  66
  67 /* Return length of current_catcher list.  */
  68
  69 static int
  70 catcher_list_size (void)
  71 {
  72   int size;
  73   struct catcher *catcher;
  74
  75   for (size = 0, catcher = current_catcher;
  76        catcher != NULL;
  77        catcher = catcher->prev)
  78     ++size;
  79
  80   return size;
  81 }
  82
  83 EXCEPTIONS_SIGJMP_BUF *
  84 exceptions_state_mc_init (volatile struct gdb_exception *exception,
  85                           return_mask mask)
  86 {
  87   struct catcher *new_catcher = XCNEW (struct catcher);
  88
  89   /* Start with no exception, save it's address.  */
  90   exception->reason = 0;
  91   exception->error = GDB_NO_ERROR;
  92   exception->message = NULL;
  93   new_catcher->exception = exception;
  94
  95   new_catcher->mask = mask;
  96
  97   /* Prevent error/quit during FUNC from calling cleanups established
  98      prior to here.  */
  99   new_catcher->saved_cleanup_chain = save_cleanups ();
 100
 101   /* Push this new catcher on the top.  */
 102   new_catcher->prev = current_catcher;
 103   current_catcher = new_catcher;
 104   new_catcher->state = CATCHER_CREATED;
 105
 106   return &new_catcher->buf;
 107 }
 108
 109 static void
 110 catcher_pop (void)
 111 {
 112   struct catcher *old_catcher = current_catcher;
 113
 114   current_catcher = old_catcher->prev;
 115
 116   /* Restore the cleanup chain, the error/quit messages, and the uiout
 117      builder, to their original states.  */
 118
 119   restore_cleanups (old_catcher->saved_cleanup_chain);
 120
 121   xfree (old_catcher);
 122 }
 123
 124 /* Catcher state machine.  Returns non-zero if the m/c should be run
 125    again, zero if it should abort.  */
 126
 127 static int
 128 exceptions_state_mc (enum catcher_action action)
 129 {
 130   switch (current_catcher->state)
 131     {
 132     case CATCHER_CREATED:
 133       switch (action)
 134         {
 135         case CATCH_ITER:
 136           /* Allow the code to run the catcher.  */
 137           current_catcher->state = CATCHER_RUNNING;
 138           return 1;
 139         default:
 140           internal_error (__FILE__, __LINE__, _("bad state"));
 141         }
 142     case CATCHER_RUNNING:
 143       switch (action)
 144         {
 145         case CATCH_ITER:
 146           /* No error/quit has occured.  Just clean up.  */
 147           catcher_pop ();
 148           return 0;
 149         case CATCH_ITER_1:
 150           current_catcher->state = CATCHER_RUNNING_1;
 151           return 1;
 152         case CATCH_THROWING:
 153           current_catcher->state = CATCHER_ABORTING;
 154           /* See also throw_exception.  */
 155           return 1;
 156         default:
 157           internal_error (__FILE__, __LINE__, _("bad switch"));
 158         }
 159     case CATCHER_RUNNING_1:
 160       switch (action)
 161         {
 162         case CATCH_ITER:
 163           /* The did a "break" from the inner while loop.  */
 164           catcher_pop ();
 165           return 0;
 166         case CATCH_ITER_1:
 167           current_catcher->state = CATCHER_RUNNING;
 168           return 0;
 169         case CATCH_THROWING:
 170           current_catcher->state = CATCHER_ABORTING;
 171           /* See also throw_exception.  */
 172           return 1;
 173         default:
 174           internal_error (__FILE__, __LINE__, _("bad switch"));
 175         }
 176     case CATCHER_ABORTING:
 177       switch (action)
 178         {
 179         case CATCH_ITER:
 180           {
 181             struct gdb_exception exception = *current_catcher->exception;
 182
 183             if (current_catcher->mask & RETURN_MASK (exception.reason))
 184               {
 185                 /* Exit normally if this catcher can handle this
 186                    exception.  The caller analyses the func return
 187                    values.  */
 188                 catcher_pop ();
 189                 return 0;
 190               }
 191             /* The caller didn't request that the event be caught,
 192                relay the event to the next containing
 193                catch_errors().  */
 194             catcher_pop ();
 195             throw_exception (exception);
 196           }
 197         default:
 198           internal_error (__FILE__, __LINE__, _("bad state"));
 199         }
 200     default:
 201       internal_error (__FILE__, __LINE__, _("bad switch"));
 202     }
 203 }
 204
 205 int
 206 exceptions_state_mc_action_iter (void)
 207 {
 208   return exceptions_state_mc (CATCH_ITER);
 209 }
 210
 211 int
 212 exceptions_state_mc_action_iter_1 (void)
 213 {
 214   return exceptions_state_mc (CATCH_ITER_1);
 215 }
 216
 217 /* Return EXCEPTION to the nearest containing catch_errors().  */
 218
 219 void
 220 throw_exception (struct gdb_exception exception)
 221 {
 222   clear_quit_flag ();
 223   immediate_quit = 0;
 224
 225   do_cleanups (all_cleanups ());
 226
 227   /* Jump to the containing catch_errors() call, communicating REASON
 228      to that call via setjmp's return value.  Note that REASON can't
 229      be zero, by definition in defs.h.  */
 230   exceptions_state_mc (CATCH_THROWING);
 231   *current_catcher->exception = exception;
 232   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 233 }
 234
 235 static void
 236 print_flush (void)
 237 {
 238   struct serial *gdb_stdout_serial;
 239
 240   if (deprecated_error_begin_hook)
 241     deprecated_error_begin_hook ();
 242   target_terminal_ours ();
 243
 244   /* We want all output to appear now, before we print the error.  We
 245      have 3 levels of buffering we have to flush (it's possible that
 246      some of these should be changed to flush the lower-level ones
 247      too):  */
 248
 249   /* 1.  The _filtered buffer.  */
 250   wrap_here ("");
 251
 252   /* 2.  The stdio buffer.  */
 253   gdb_flush (gdb_stdout);
 254   gdb_flush (gdb_stderr);
 255
 256   /* 3.  The system-level buffer.  */
 257   gdb_stdout_serial = serial_fdopen (1);
 258   if (gdb_stdout_serial)
 259     {
 260       serial_drain_output (gdb_stdout_serial);
 261       serial_un_fdopen (gdb_stdout_serial);
 262     }
 263
 264   annotate_error_begin ();
 265 }
 266
 267 static void
 268 print_exception (struct ui_file *file, struct gdb_exception e)
 269 {
 270   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 271      as that way the MI's behavior is preserved.  */
 272   const char *start;
 273   const char *end;
 274
 275   for (start = e.message; start != NULL; start = end)
 276     {
 277       end = strchr (start, '\n');
 278       if (end == NULL)
 279         fputs_filtered (start, file);
 280       else
 281         {
 282           end++;
 283           ui_file_write (file, start, end - start);
 284         }
 285     }
 286   fprintf_filtered (file, "\n");
 287
 288   /* Now append the annotation.  */
 289   switch (e.reason)
 290     {
 291     case RETURN_QUIT:
 292       annotate_quit ();
 293       break;
 294     case RETURN_ERROR:
 295       /* Assume that these are all errors.  */
 296       annotate_error ();
 297       break;
 298     default:
 299       internal_error (__FILE__, __LINE__, _("Bad switch."));
 300     }
 301 }
 302
 303 void
 304 exception_print (struct ui_file *file, struct gdb_exception e)
 305 {
 306   if (e.reason < 0 && e.message != NULL)
 307     {
 308       print_flush ();
 309       print_exception (file, e);
 310     }
 311 }
 312
 313 void
 314 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 315                    const char *prefix, ...)
 316 {
 317   if (e.reason < 0 && e.message != NULL)
 318     {
 319       va_list args;
 320
 321       print_flush ();
 322
 323       /* Print the prefix.  */
 324       va_start (args, prefix);
 325       vfprintf_filtered (file, prefix, args);
 326       va_end (args);
 327
 328       print_exception (file, e);
 329     }
 330 }
 331
 332 /* A stack of exception messages.
 333    This is needed to handle nested calls to throw_it: we don't want to
 334    xfree space for a message before it's used.
 335    This can happen if we throw an exception during a cleanup:
 336    An outer TRY_CATCH may have an exception message it wants to print,
 337    but while doing cleanups further calls to throw_it are made.
 338
 339    This is indexed by the size of the current_catcher list.
 340    It is a dynamically allocated array so that we don't care how deeply
 341    GDB nests its TRY_CATCHs.  */
 342 static char **exception_messages;
 343
 344 /* The number of currently allocated entries in exception_messages.  */
 345 static int exception_messages_size;
 346
 347 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 348 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 349           va_list ap)
 350 {
 351   struct gdb_exception e;
 352   char *new_message;
 353   int depth = catcher_list_size ();
 354
 355   gdb_assert (depth > 0);
 356
 357   /* Note: The new message may use an old message's text.  */
 358   new_message = xstrvprintf (fmt, ap);
 359
 360   if (depth > exception_messages_size)
 361     {
 362       int old_size = exception_messages_size;
 363
 364       exception_messages_size = depth + 10;
 365       exception_messages = (char **) xrealloc (exception_messages,
 366                                                exception_messages_size
 367                                                * sizeof (char *));
 368       memset (exception_messages + old_size, 0,
 369               (exception_messages_size - old_size) * sizeof (char *));
 370     }
 371
 372   xfree (exception_messages[depth - 1]);
 373   exception_messages[depth - 1] = new_message;
 374
 375   /* Create the exception.  */
 376   e.reason = reason;
 377   e.error = error;
 378   e.message = new_message;
 379
 380   /* Throw the exception.  */
 381   throw_exception (e);
 382 }
 383
 384 void
 385 throw_verror (enum errors error, const char *fmt, va_list ap)
 386 {
 387   throw_it (RETURN_ERROR, error, fmt, ap);
 388 }
 389
 390 void
 391 throw_vquit (const char *fmt, va_list ap)
 392 {
 393   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 394 }
 395
 396 void
 397 throw_error (enum errors error, const char *fmt, ...)
 398 {
 399   va_list args;
 400
 401   va_start (args, fmt);
 402   throw_verror (error, fmt, args);
 403   va_end (args);
 404 }
 405
 406 void
 407 throw_quit (const char *fmt, ...)
 408 {
 409   va_list args;
 410
 411   va_start (args, fmt);
 412   throw_vquit (fmt, args);
 413   va_end (args);
 414 }
 415
 416 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 417    handler.  If an exception (enum return_reason) is thrown using
 418    throw_exception() than all cleanups installed since
 419    catch_exceptions() was entered are invoked, the (-ve) exception
 420    value is then returned by catch_exceptions.  If FUNC() returns
 421    normally (with a positive or zero return value) then that value is
 422    returned by catch_exceptions().  It is an internal_error() for
 423    FUNC() to return a negative value.
 424
 425    See exceptions.h for further usage details.
 426
 427    Must not be called with immediate_quit in effect (bad things might
 428    happen, say we got a signal in the middle of a memcpy to quit_return).
 429    This is an OK restriction; with very few exceptions immediate_quit can
 430    be replaced by judicious use of QUIT.  */
 431
 432 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 433    error() et al. could maintain a set of flags that indicate the
 434    current state of each of the longjmp buffers.  This would give the
 435    longjmp code the chance to detect a longjmp botch (before it gets
 436    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 437    code also randomly used a SET_TOP_LEVEL macro that directly
 438    initialized the longjmp buffers.  */
 439
 440 int
 441 catch_exceptions (struct ui_out *uiout,
 442                   catch_exceptions_ftype *func,
 443                   void *func_args,
 444                   return_mask mask)
 445 {
 446   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 447 }
 448
 449 int
 450 catch_exceptions_with_msg (struct ui_out *func_uiout,
 451                            catch_exceptions_ftype *func,
 452                            void *func_args,
 453                            char **gdberrmsg,
 454                            return_mask mask)
 455 {
 456   volatile struct gdb_exception exception;
 457   volatile int val = 0;
 458   struct ui_out *saved_uiout;
 459
 460   /* Save and override the global ``struct ui_out'' builder.  */
 461   saved_uiout = current_uiout;
 462   current_uiout = func_uiout;
 463
 464   TRY_CATCH (exception, RETURN_MASK_ALL)
 465     {
 466       val = (*func) (current_uiout, func_args);
 467     }
 468
 469   /* Restore the global builder.  */
 470   current_uiout = saved_uiout;
 471
 472   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 473     {
 474       /* The caller didn't request that the event be caught.
 475          Rethrow.  */
 476       throw_exception (exception);
 477     }
 478
 479   exception_print (gdb_stderr, exception);
 480   gdb_assert (val >= 0);
 481   gdb_assert (exception.reason <= 0);
 482   if (exception.reason < 0)
 483     {
 484       /* If caller wants a copy of the low-level error message, make
 485          one.  This is used in the case of a silent error whereby the
 486          caller may optionally want to issue the message.  */
 487       if (gdberrmsg != NULL)
 488         {
 489           if (exception.message != NULL)
 490             *gdberrmsg = xstrdup (exception.message);
 491           else
 492             *gdberrmsg = NULL;
 493         }
 494       return exception.reason;
 495     }
 496   return val;
 497 }
 498
 499 /* This function is superseded by catch_exceptions().  */
 500
 501 int
 502 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 503               return_mask mask)
 504 {
 505   volatile int val = 0;
 506   volatile struct gdb_exception exception;
 507   struct ui_out *saved_uiout;
 508
 509   /* Save the global ``struct ui_out'' builder.  */
 510   saved_uiout = current_uiout;
 511
 512   TRY_CATCH (exception, RETURN_MASK_ALL)
 513     {
 514       val = func (func_args);
 515     }
 516
 517   /* Restore the global builder.  */
 518   current_uiout = saved_uiout;
 519
 520   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 521     {
 522       /* The caller didn't request that the event be caught.
 523          Rethrow.  */
 524       throw_exception (exception);
 525     }
 526
 527   exception_fprintf (gdb_stderr, exception, "%s", errstring);
 528   if (exception.reason != 0)
 529     return 0;
 530   return val;
 531 }