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