gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986, 1988-2012 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 "gdb_assert.h"
  28 #include "gdb_string.h"
  29 #include "serial.h"
  30 #include "gdbthread.h"
  31
  32 const struct gdb_exception exception_none = { 0, GDB_NO_ERROR, NULL };
  33
  34 /* Possible catcher states.  */
  35 enum catcher_state {
  36   /* Initial state, a new catcher has just been created.  */
  37   CATCHER_CREATED,
  38   /* The catch code is running.  */
  39   CATCHER_RUNNING,
  40   CATCHER_RUNNING_1,
  41   /* The catch code threw an exception.  */
  42   CATCHER_ABORTING
  43 };
  44
  45 /* Possible catcher actions.  */
  46 enum catcher_action {
  47   CATCH_ITER,
  48   CATCH_ITER_1,
  49   CATCH_THROWING
  50 };
  51
  52 struct catcher
  53 {
  54   enum catcher_state state;
  55   /* Jump buffer pointing back at the exception handler.  */
  56   EXCEPTIONS_SIGJMP_BUF buf;
  57   /* Status buffer belonging to the exception handler.  */
  58   volatile struct gdb_exception *exception;
  59   /* Saved/current state.  */
  60   int mask;
  61   struct cleanup *saved_cleanup_chain;
  62   /* Back link.  */
  63   struct catcher *prev;
  64 };
  65
  66 /* Where to go for throw_exception().  */
  67 static struct catcher *current_catcher;
  68
  69 /* Return length of current_catcher list.  */
  70
  71 static int
  72 catcher_list_size (void)
  73 {
  74   int size;
  75   struct catcher *catcher;
  76
  77   for (size = 0, catcher = current_catcher;
  78        catcher != NULL;
  79        catcher = catcher->prev)
  80     ++size;
  81
  82   return size;
  83 }
  84
  85 EXCEPTIONS_SIGJMP_BUF *
  86 exceptions_state_mc_init (volatile struct gdb_exception *exception,
  87                           return_mask mask)
  88 {
  89   struct catcher *new_catcher = XZALLOC (struct catcher);
  90
  91   /* Start with no exception, save it's address.  */
  92   exception->reason = 0;
  93   exception->error = GDB_NO_ERROR;
  94   exception->message = NULL;
  95   new_catcher->exception = exception;
  96
  97   new_catcher->mask = mask;
  98
  99   /* Prevent error/quit during FUNC from calling cleanups established
 100      prior to here.  */
 101   new_catcher->saved_cleanup_chain = save_cleanups ();
 102
 103   /* Push this new catcher on the top.  */
 104   new_catcher->prev = current_catcher;
 105   current_catcher = new_catcher;
 106   new_catcher->state = CATCHER_CREATED;
 107
 108   return &new_catcher->buf;
 109 }
 110
 111 static void
 112 catcher_pop (void)
 113 {
 114   struct catcher *old_catcher = current_catcher;
 115
 116   current_catcher = old_catcher->prev;
 117
 118   /* Restore the cleanup chain, the error/quit messages, and the uiout
 119      builder, to their original states.  */
 120
 121   restore_cleanups (old_catcher->saved_cleanup_chain);
 122
 123   xfree (old_catcher);
 124 }
 125
 126 /* Catcher state machine.  Returns non-zero if the m/c should be run
 127    again, zero if it should abort.  */
 128
 129 static int
 130 exceptions_state_mc (enum catcher_action action)
 131 {
 132   switch (current_catcher->state)
 133     {
 134     case CATCHER_CREATED:
 135       switch (action)
 136         {
 137         case CATCH_ITER:
 138           /* Allow the code to run the catcher.  */
 139           current_catcher->state = CATCHER_RUNNING;
 140           return 1;
 141         default:
 142           internal_error (__FILE__, __LINE__, _("bad state"));
 143         }
 144     case CATCHER_RUNNING:
 145       switch (action)
 146         {
 147         case CATCH_ITER:
 148           /* No error/quit has occured.  Just clean up.  */
 149           catcher_pop ();
 150           return 0;
 151         case CATCH_ITER_1:
 152           current_catcher->state = CATCHER_RUNNING_1;
 153           return 1;
 154         case CATCH_THROWING:
 155           current_catcher->state = CATCHER_ABORTING;
 156           /* See also throw_exception.  */
 157           return 1;
 158         default:
 159           internal_error (__FILE__, __LINE__, _("bad switch"));
 160         }
 161     case CATCHER_RUNNING_1:
 162       switch (action)
 163         {
 164         case CATCH_ITER:
 165           /* The did a "break" from the inner while loop.  */
 166           catcher_pop ();
 167           return 0;
 168         case CATCH_ITER_1:
 169           current_catcher->state = CATCHER_RUNNING;
 170           return 0;
 171         case CATCH_THROWING:
 172           current_catcher->state = CATCHER_ABORTING;
 173           /* See also throw_exception.  */
 174           return 1;
 175         default:
 176           internal_error (__FILE__, __LINE__, _("bad switch"));
 177         }
 178     case CATCHER_ABORTING:
 179       switch (action)
 180         {
 181         case CATCH_ITER:
 182           {
 183             struct gdb_exception exception = *current_catcher->exception;
 184
 185             if (current_catcher->mask & RETURN_MASK (exception.reason))
 186               {
 187                 /* Exit normally if this catcher can handle this
 188                    exception.  The caller analyses the func return
 189                    values.  */
 190                 catcher_pop ();
 191                 return 0;
 192               }
 193             /* The caller didn't request that the event be caught,
 194                relay the event to the next containing
 195                catch_errors().  */
 196             catcher_pop ();
 197             throw_exception (exception);
 198           }
 199         default:
 200           internal_error (__FILE__, __LINE__, _("bad state"));
 201         }
 202     default:
 203       internal_error (__FILE__, __LINE__, _("bad switch"));
 204     }
 205 }
 206
 207 int
 208 exceptions_state_mc_action_iter (void)
 209 {
 210   return exceptions_state_mc (CATCH_ITER);
 211 }
 212
 213 int
 214 exceptions_state_mc_action_iter_1 (void)
 215 {
 216   return exceptions_state_mc (CATCH_ITER_1);
 217 }
 218
 219 /* Return EXCEPTION to the nearest containing catch_errors().  */
 220
 221 void
 222 throw_exception (struct gdb_exception exception)
 223 {
 224   clear_quit_flag ();
 225   immediate_quit = 0;
 226
 227   do_cleanups (all_cleanups ());
 228
 229   /* Jump to the containing catch_errors() call, communicating REASON
 230      to that call via setjmp's return value.  Note that REASON can't
 231      be zero, by definition in defs.h.  */
 232   exceptions_state_mc (CATCH_THROWING);
 233   *current_catcher->exception = exception;
 234   EXCEPTIONS_SIGLONGJMP (current_catcher->buf, exception.reason);
 235 }
 236
 237 void
 238 deprecated_throw_reason (enum return_reason reason)
 239 {
 240   struct gdb_exception exception;
 241
 242   memset (&exception, 0, sizeof exception);
 243
 244   exception.reason = reason;
 245   switch (reason)
 246     {
 247     case RETURN_QUIT:
 248       break;
 249     case RETURN_ERROR:
 250       exception.error = GENERIC_ERROR;
 251       break;
 252     default:
 253       internal_error (__FILE__, __LINE__, _("bad switch"));
 254     }
 255
 256   throw_exception (exception);
 257 }
 258
 259 static void
 260 print_flush (void)
 261 {
 262   struct serial *gdb_stdout_serial;
 263
 264   if (deprecated_error_begin_hook)
 265     deprecated_error_begin_hook ();
 266   target_terminal_ours ();
 267
 268   /* We want all output to appear now, before we print the error.  We
 269      have 3 levels of buffering we have to flush (it's possible that
 270      some of these should be changed to flush the lower-level ones
 271      too):  */
 272
 273   /* 1.  The _filtered buffer.  */
 274   wrap_here ("");
 275
 276   /* 2.  The stdio buffer.  */
 277   gdb_flush (gdb_stdout);
 278   gdb_flush (gdb_stderr);
 279
 280   /* 3.  The system-level buffer.  */
 281   gdb_stdout_serial = serial_fdopen (1);
 282   if (gdb_stdout_serial)
 283     {
 284       serial_drain_output (gdb_stdout_serial);
 285       serial_un_fdopen (gdb_stdout_serial);
 286     }
 287
 288   annotate_error_begin ();
 289 }
 290
 291 static void
 292 print_exception (struct ui_file *file, struct gdb_exception e)
 293 {
 294   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 295      as that way the MI's behavior is preserved.  */
 296   const char *start;
 297   const char *end;
 298
 299   for (start = e.message; start != NULL; start = end)
 300     {
 301       end = strchr (start, '\n');
 302       if (end == NULL)
 303         fputs_filtered (start, file);
 304       else
 305         {
 306           end++;
 307           ui_file_write (file, start, end - start);
 308         }
 309     }
 310   fprintf_filtered (file, "\n");
 311
 312   /* Now append the annotation.  */
 313   switch (e.reason)
 314     {
 315     case RETURN_QUIT:
 316       annotate_quit ();
 317       break;
 318     case RETURN_ERROR:
 319       /* Assume that these are all errors.  */
 320       annotate_error ();
 321       break;
 322     default:
 323       internal_error (__FILE__, __LINE__, _("Bad switch."));
 324     }
 325 }
 326
 327 void
 328 exception_print (struct ui_file *file, struct gdb_exception e)
 329 {
 330   if (e.reason < 0 && e.message != NULL)
 331     {
 332       print_flush ();
 333       print_exception (file, e);
 334     }
 335 }
 336
 337 void
 338 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 339                    const char *prefix, ...)
 340 {
 341   if (e.reason < 0 && e.message != NULL)
 342     {
 343       va_list args;
 344
 345       print_flush ();
 346
 347       /* Print the prefix.  */
 348       va_start (args, prefix);
 349       vfprintf_filtered (file, prefix, args);
 350       va_end (args);
 351
 352       print_exception (file, e);
 353     }
 354 }
 355
 356 static void
 357 print_any_exception (struct ui_file *file, const char *prefix,
 358                      struct gdb_exception e)
 359 {
 360   if (e.reason < 0 && e.message != NULL)
 361     {
 362       target_terminal_ours ();
 363       wrap_here ("");           /* Force out any buffered output.  */
 364       gdb_flush (gdb_stdout);
 365       annotate_error_begin ();
 366
 367       /* Print the prefix.  */
 368       if (prefix != NULL && prefix[0] != '\0')
 369         fputs_filtered (prefix, file);
 370       print_exception (file, e);
 371     }
 372 }
 373
 374 /* A stack of exception messages.
 375    This is needed to handle nested calls to throw_it: we don't want to
 376    xfree space for a message before it's used.
 377    This can happen if we throw an exception during a cleanup:
 378    An outer TRY_CATCH may have an exception message it wants to print,
 379    but while doing cleanups further calls to throw_it are made.
 380
 381    This is indexed by the size of the current_catcher list.
 382    It is a dynamically allocated array so that we don't care how deeply
 383    GDB nests its TRY_CATCHs.  */
 384 static char **exception_messages;
 385
 386 /* The number of currently allocated entries in exception_messages.  */
 387 static int exception_messages_size;
 388
 389 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 390 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 391           va_list ap)
 392 {
 393   struct gdb_exception e;
 394   char *new_message;
 395   int depth = catcher_list_size ();
 396
 397   gdb_assert (depth > 0);
 398
 399   /* Note: The new message may use an old message's text.  */
 400   new_message = xstrvprintf (fmt, ap);
 401
 402   if (depth > exception_messages_size)
 403     {
 404       int old_size = exception_messages_size;
 405
 406       exception_messages_size = depth + 10;
 407       exception_messages = (char **) xrealloc (exception_messages,
 408                                                exception_messages_size
 409                                                * sizeof (char *));
 410       memset (exception_messages + old_size, 0,
 411               (exception_messages_size - old_size) * sizeof (char *));
 412     }
 413
 414   xfree (exception_messages[depth - 1]);
 415   exception_messages[depth - 1] = new_message;
 416
 417   /* Create the exception.  */
 418   e.reason = reason;
 419   e.error = error;
 420   e.message = new_message;
 421
 422   /* Throw the exception.  */
 423   throw_exception (e);
 424 }
 425
 426 void
 427 throw_verror (enum errors error, const char *fmt, va_list ap)
 428 {
 429   throw_it (RETURN_ERROR, error, fmt, ap);
 430 }
 431
 432 void
 433 throw_vfatal (const char *fmt, va_list ap)
 434 {
 435   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 436 }
 437
 438 void
 439 throw_error (enum errors error, const char *fmt, ...)
 440 {
 441   va_list args;
 442
 443   va_start (args, fmt);
 444   throw_it (RETURN_ERROR, error, fmt, args);
 445   va_end (args);
 446 }
 447
 448 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 449    handler.  If an exception (enum return_reason) is thrown using
 450    throw_exception() than all cleanups installed since
 451    catch_exceptions() was entered are invoked, the (-ve) exception
 452    value is then returned by catch_exceptions.  If FUNC() returns
 453    normally (with a positive or zero return value) then that value is
 454    returned by catch_exceptions().  It is an internal_error() for
 455    FUNC() to return a negative value.
 456
 457    See exceptions.h for further usage details.
 458
 459    Must not be called with immediate_quit in effect (bad things might
 460    happen, say we got a signal in the middle of a memcpy to quit_return).
 461    This is an OK restriction; with very few exceptions immediate_quit can
 462    be replaced by judicious use of QUIT.  */
 463
 464 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 465    error() et al. could maintain a set of flags that indicate the
 466    current state of each of the longjmp buffers.  This would give the
 467    longjmp code the chance to detect a longjmp botch (before it gets
 468    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 469    code also randomly used a SET_TOP_LEVEL macro that directly
 470    initialized the longjmp buffers.  */
 471
 472 int
 473 catch_exceptions (struct ui_out *uiout,
 474                   catch_exceptions_ftype *func,
 475                   void *func_args,
 476                   return_mask mask)
 477 {
 478   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 479 }
 480
 481 int
 482 catch_exceptions_with_msg (struct ui_out *func_uiout,
 483                            catch_exceptions_ftype *func,
 484                            void *func_args,
 485                            char **gdberrmsg,
 486                            return_mask mask)
 487 {
 488   volatile struct gdb_exception exception;
 489   volatile int val = 0;
 490   struct ui_out *saved_uiout;
 491
 492   /* Save and override the global ``struct ui_out'' builder.  */
 493   saved_uiout = current_uiout;
 494   current_uiout = func_uiout;
 495
 496   TRY_CATCH (exception, RETURN_MASK_ALL)
 497     {
 498       val = (*func) (current_uiout, func_args);
 499     }
 500
 501   /* Restore the global builder.  */
 502   current_uiout = saved_uiout;
 503
 504   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 505     {
 506       /* The caller didn't request that the event be caught.
 507          Rethrow.  */
 508       throw_exception (exception);
 509     }
 510
 511   print_any_exception (gdb_stderr, NULL, exception);
 512   gdb_assert (val >= 0);
 513   gdb_assert (exception.reason <= 0);
 514   if (exception.reason < 0)
 515     {
 516       /* If caller wants a copy of the low-level error message, make
 517          one.  This is used in the case of a silent error whereby the
 518          caller may optionally want to issue the message.  */
 519       if (gdberrmsg != NULL)
 520         {
 521           if (exception.message != NULL)
 522             *gdberrmsg = xstrdup (exception.message);
 523           else
 524             *gdberrmsg = NULL;
 525         }
 526       return exception.reason;
 527     }
 528   return val;
 529 }
 530
 531 /* This function is superseded by catch_exceptions().  */
 532
 533 int
 534 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 535               return_mask mask)
 536 {
 537   volatile int val = 0;
 538   volatile struct gdb_exception exception;
 539   struct ui_out *saved_uiout;
 540
 541   /* Save the global ``struct ui_out'' builder.  */
 542   saved_uiout = current_uiout;
 543
 544   TRY_CATCH (exception, RETURN_MASK_ALL)
 545     {
 546       val = func (func_args);
 547     }
 548
 549   /* Restore the global builder.  */
 550   current_uiout = saved_uiout;
 551
 552   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 553     {
 554       /* The caller didn't request that the event be caught.
 555          Rethrow.  */
 556       throw_exception (exception);
 557     }
 558
 559   print_any_exception (gdb_stderr, errstring, exception);
 560   if (exception.reason != 0)
 561     return 0;
 562   return val;
 563 }
 564
 565 int
 566 catch_command_errors (catch_command_errors_ftype * command,
 567                       char *arg, int from_tty, return_mask mask)
 568 {
 569   volatile struct gdb_exception e;
 570
 571   TRY_CATCH (e, mask)
 572     {
 573       command (arg, from_tty);
 574     }
 575   print_any_exception (gdb_stderr, NULL, e);
 576   if (e.reason < 0)
 577     return 0;
 578   return 1;
 579 }