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   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 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   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
 243   if (target_supports_terminal_ours ())
 244     target_terminal_ours ();
 245
 246   /* We want all output to appear now, before we print the error.  We
 247      have 3 levels of buffering we have to flush (it's possible that
 248      some of these should be changed to flush the lower-level ones
 249      too):  */
 250
 251   /* 1.  The _filtered buffer.  */
 252   if (filtered_printing_initialized ())
 253     wrap_here ("");
 254
 255   /* 2.  The stdio buffer.  */
 256   gdb_flush (gdb_stdout);
 257   gdb_flush (gdb_stderr);
 258
 259   /* 3.  The system-level buffer.  */
 260   gdb_stdout_serial = serial_fdopen (1);
 261   if (gdb_stdout_serial)
 262     {
 263       serial_drain_output (gdb_stdout_serial);
 264       serial_un_fdopen (gdb_stdout_serial);
 265     }
 266
 267   annotate_error_begin ();
 268 }
 269
 270 static void
 271 print_exception (struct ui_file *file, struct gdb_exception e)
 272 {
 273   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 274      as that way the MI's behavior is preserved.  */
 275   const char *start;
 276   const char *end;
 277
 278   for (start = e.message; start != NULL; start = end)
 279     {
 280       end = strchr (start, '\n');
 281       if (end == NULL)
 282         fputs_filtered (start, file);
 283       else
 284         {
 285           end++;
 286           ui_file_write (file, start, end - start);
 287         }
 288     }
 289   fprintf_filtered (file, "\n");
 290
 291   /* Now append the annotation.  */
 292   switch (e.reason)
 293     {
 294     case RETURN_QUIT:
 295       annotate_quit ();
 296       break;
 297     case RETURN_ERROR:
 298       /* Assume that these are all errors.  */
 299       annotate_error ();
 300       break;
 301     default:
 302       internal_error (__FILE__, __LINE__, _("Bad switch."));
 303     }
 304 }
 305
 306 void
 307 exception_print (struct ui_file *file, struct gdb_exception e)
 308 {
 309   if (e.reason < 0 && e.message != NULL)
 310     {
 311       print_flush ();
 312       print_exception (file, e);
 313     }
 314 }
 315
 316 void
 317 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 318                    const char *prefix, ...)
 319 {
 320   if (e.reason < 0 && e.message != NULL)
 321     {
 322       va_list args;
 323
 324       print_flush ();
 325
 326       /* Print the prefix.  */
 327       va_start (args, prefix);
 328       vfprintf_filtered (file, prefix, args);
 329       va_end (args);
 330
 331       print_exception (file, e);
 332     }
 333 }
 334
 335 /* A stack of exception messages.
 336    This is needed to handle nested calls to throw_it: we don't want to
 337    xfree space for a message before it's used.
 338    This can happen if we throw an exception during a cleanup:
 339    An outer TRY_CATCH may have an exception message it wants to print,
 340    but while doing cleanups further calls to throw_it are made.
 341
 342    This is indexed by the size of the current_catcher list.
 343    It is a dynamically allocated array so that we don't care how deeply
 344    GDB nests its TRY_CATCHs.  */
 345 static char **exception_messages;
 346
 347 /* The number of currently allocated entries in exception_messages.  */
 348 static int exception_messages_size;
 349
 350 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 351 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 352           va_list ap)
 353 {
 354   struct gdb_exception e;
 355   char *new_message;
 356   int depth = catcher_list_size ();
 357
 358   gdb_assert (depth > 0);
 359
 360   /* Note: The new message may use an old message's text.  */
 361   new_message = xstrvprintf (fmt, ap);
 362
 363   if (depth > exception_messages_size)
 364     {
 365       int old_size = exception_messages_size;
 366
 367       exception_messages_size = depth + 10;
 368       exception_messages = (char **) xrealloc (exception_messages,
 369                                                exception_messages_size
 370                                                * sizeof (char *));
 371       memset (exception_messages + old_size, 0,
 372               (exception_messages_size - old_size) * sizeof (char *));
 373     }
 374
 375   xfree (exception_messages[depth - 1]);
 376   exception_messages[depth - 1] = new_message;
 377
 378   /* Create the exception.  */
 379   e.reason = reason;
 380   e.error = error;
 381   e.message = new_message;
 382
 383   /* Throw the exception.  */
 384   throw_exception (e);
 385 }
 386
 387 void
 388 throw_verror (enum errors error, const char *fmt, va_list ap)
 389 {
 390   throw_it (RETURN_ERROR, error, fmt, ap);
 391 }
 392
 393 void
 394 throw_vquit (const char *fmt, va_list ap)
 395 {
 396   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 397 }
 398
 399 void
 400 throw_error (enum errors error, const char *fmt, ...)
 401 {
 402   va_list args;
 403
 404   va_start (args, fmt);
 405   throw_verror (error, fmt, args);
 406   va_end (args);
 407 }
 408
 409 void
 410 throw_quit (const char *fmt, ...)
 411 {
 412   va_list args;
 413
 414   va_start (args, fmt);
 415   throw_vquit (fmt, args);
 416   va_end (args);
 417 }
 418
 419 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 420    handler.  If an exception (enum return_reason) is thrown using
 421    throw_exception() than all cleanups installed since
 422    catch_exceptions() was entered are invoked, the (-ve) exception
 423    value is then returned by catch_exceptions.  If FUNC() returns
 424    normally (with a positive or zero return value) then that value is
 425    returned by catch_exceptions().  It is an internal_error() for
 426    FUNC() to return a negative value.
 427
 428    See exceptions.h for further usage details.
 429
 430    Must not be called with immediate_quit in effect (bad things might
 431    happen, say we got a signal in the middle of a memcpy to quit_return).
 432    This is an OK restriction; with very few exceptions immediate_quit can
 433    be replaced by judicious use of QUIT.  */
 434
 435 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 436    error() et al. could maintain a set of flags that indicate the
 437    current state of each of the longjmp buffers.  This would give the
 438    longjmp code the chance to detect a longjmp botch (before it gets
 439    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 440    code also randomly used a SET_TOP_LEVEL macro that directly
 441    initialized the longjmp buffers.  */
 442
 443 int
 444 catch_exceptions (struct ui_out *uiout,
 445                   catch_exceptions_ftype *func,
 446                   void *func_args,
 447                   return_mask mask)
 448 {
 449   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 450 }
 451
 452 int
 453 catch_exceptions_with_msg (struct ui_out *func_uiout,
 454                            catch_exceptions_ftype *func,
 455                            void *func_args,
 456                            char **gdberrmsg,
 457                            return_mask mask)
 458 {
 459   volatile struct gdb_exception exception;
 460   volatile int val = 0;
 461   struct ui_out *saved_uiout;
 462
 463   /* Save and override the global ``struct ui_out'' builder.  */
 464   saved_uiout = current_uiout;
 465   current_uiout = func_uiout;
 466
 467   TRY_CATCH (exception, RETURN_MASK_ALL)
 468     {
 469       val = (*func) (current_uiout, func_args);
 470     }
 471
 472   /* Restore the global builder.  */
 473   current_uiout = saved_uiout;
 474
 475   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 476     {
 477       /* The caller didn't request that the event be caught.
 478          Rethrow.  */
 479       throw_exception (exception);
 480     }
 481
 482   exception_print (gdb_stderr, exception);
 483   gdb_assert (val >= 0);
 484   gdb_assert (exception.reason <= 0);
 485   if (exception.reason < 0)
 486     {
 487       /* If caller wants a copy of the low-level error message, make
 488          one.  This is used in the case of a silent error whereby the
 489          caller may optionally want to issue the message.  */
 490       if (gdberrmsg != NULL)
 491         {
 492           if (exception.message != NULL)
 493             *gdberrmsg = xstrdup (exception.message);
 494           else
 495             *gdberrmsg = NULL;
 496         }
 497       return exception.reason;
 498     }
 499   return val;
 500 }
 501
 502 /* This function is superseded by catch_exceptions().  */
 503
 504 int
 505 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 506               return_mask mask)
 507 {
 508   volatile int val = 0;
 509   volatile struct gdb_exception exception;
 510   struct ui_out *saved_uiout;
 511
 512   /* Save the global ``struct ui_out'' builder.  */
 513   saved_uiout = current_uiout;
 514
 515   TRY_CATCH (exception, RETURN_MASK_ALL)
 516     {
 517       val = func (func_args);
 518     }
 519
 520   /* Restore the global builder.  */
 521   current_uiout = saved_uiout;
 522
 523   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 524     {
 525       /* The caller didn't request that the event be caught.
 526          Rethrow.  */
 527       throw_exception (exception);
 528     }
 529
 530   exception_fprintf (gdb_stderr, exception, "%s", errstring);
 531   if (exception.reason != 0)
 532     return 0;
 533   return val;
 534 }