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 "gdb_assert.h"
  28 #include <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 = XCNEW (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 static void
 238 print_flush (void)
 239 {
 240   struct serial *gdb_stdout_serial;
 241
 242   if (deprecated_error_begin_hook)
 243     deprecated_error_begin_hook ();
 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   wrap_here ("");
 253
 254   /* 2.  The stdio buffer.  */
 255   gdb_flush (gdb_stdout);
 256   gdb_flush (gdb_stderr);
 257
 258   /* 3.  The system-level buffer.  */
 259   gdb_stdout_serial = serial_fdopen (1);
 260   if (gdb_stdout_serial)
 261     {
 262       serial_drain_output (gdb_stdout_serial);
 263       serial_un_fdopen (gdb_stdout_serial);
 264     }
 265
 266   annotate_error_begin ();
 267 }
 268
 269 static void
 270 print_exception (struct ui_file *file, struct gdb_exception e)
 271 {
 272   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 273      as that way the MI's behavior is preserved.  */
 274   const char *start;
 275   const char *end;
 276
 277   for (start = e.message; start != NULL; start = end)
 278     {
 279       end = strchr (start, '\n');
 280       if (end == NULL)
 281         fputs_filtered (start, file);
 282       else
 283         {
 284           end++;
 285           ui_file_write (file, start, end - start);
 286         }
 287     }
 288   fprintf_filtered (file, "\n");
 289
 290   /* Now append the annotation.  */
 291   switch (e.reason)
 292     {
 293     case RETURN_QUIT:
 294       annotate_quit ();
 295       break;
 296     case RETURN_ERROR:
 297       /* Assume that these are all errors.  */
 298       annotate_error ();
 299       break;
 300     default:
 301       internal_error (__FILE__, __LINE__, _("Bad switch."));
 302     }
 303 }
 304
 305 void
 306 exception_print (struct ui_file *file, struct gdb_exception e)
 307 {
 308   if (e.reason < 0 && e.message != NULL)
 309     {
 310       print_flush ();
 311       print_exception (file, e);
 312     }
 313 }
 314
 315 void
 316 exception_fprintf (struct ui_file *file, struct gdb_exception e,
 317                    const char *prefix, ...)
 318 {
 319   if (e.reason < 0 && e.message != NULL)
 320     {
 321       va_list args;
 322
 323       print_flush ();
 324
 325       /* Print the prefix.  */
 326       va_start (args, prefix);
 327       vfprintf_filtered (file, prefix, args);
 328       va_end (args);
 329
 330       print_exception (file, e);
 331     }
 332 }
 333
 334 /* A stack of exception messages.
 335    This is needed to handle nested calls to throw_it: we don't want to
 336    xfree space for a message before it's used.
 337    This can happen if we throw an exception during a cleanup:
 338    An outer TRY_CATCH may have an exception message it wants to print,
 339    but while doing cleanups further calls to throw_it are made.
 340
 341    This is indexed by the size of the current_catcher list.
 342    It is a dynamically allocated array so that we don't care how deeply
 343    GDB nests its TRY_CATCHs.  */
 344 static char **exception_messages;
 345
 346 /* The number of currently allocated entries in exception_messages.  */
 347 static int exception_messages_size;
 348
 349 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 350 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 351           va_list ap)
 352 {
 353   struct gdb_exception e;
 354   char *new_message;
 355   int depth = catcher_list_size ();
 356
 357   gdb_assert (depth > 0);
 358
 359   /* Note: The new message may use an old message's text.  */
 360   new_message = xstrvprintf (fmt, ap);
 361
 362   if (depth > exception_messages_size)
 363     {
 364       int old_size = exception_messages_size;
 365
 366       exception_messages_size = depth + 10;
 367       exception_messages = (char **) xrealloc (exception_messages,
 368                                                exception_messages_size
 369                                                * sizeof (char *));
 370       memset (exception_messages + old_size, 0,
 371               (exception_messages_size - old_size) * sizeof (char *));
 372     }
 373
 374   xfree (exception_messages[depth - 1]);
 375   exception_messages[depth - 1] = new_message;
 376
 377   /* Create the exception.  */
 378   e.reason = reason;
 379   e.error = error;
 380   e.message = new_message;
 381
 382   /* Throw the exception.  */
 383   throw_exception (e);
 384 }
 385
 386 void
 387 throw_verror (enum errors error, const char *fmt, va_list ap)
 388 {
 389   throw_it (RETURN_ERROR, error, fmt, ap);
 390 }
 391
 392 void
 393 throw_vquit (const char *fmt, va_list ap)
 394 {
 395   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 396 }
 397
 398 void
 399 throw_error (enum errors error, const char *fmt, ...)
 400 {
 401   va_list args;
 402
 403   va_start (args, fmt);
 404   throw_verror (error, fmt, args);
 405   va_end (args);
 406 }
 407
 408 void
 409 throw_quit (const char *fmt, ...)
 410 {
 411   va_list args;
 412
 413   va_start (args, fmt);
 414   throw_vquit (fmt, args);
 415   va_end (args);
 416 }
 417
 418 /* Call FUNC(UIOUT, FUNC_ARGS) but wrapped within an exception
 419    handler.  If an exception (enum return_reason) is thrown using
 420    throw_exception() than all cleanups installed since
 421    catch_exceptions() was entered are invoked, the (-ve) exception
 422    value is then returned by catch_exceptions.  If FUNC() returns
 423    normally (with a positive or zero return value) then that value is
 424    returned by catch_exceptions().  It is an internal_error() for
 425    FUNC() to return a negative value.
 426
 427    See exceptions.h for further usage details.
 428
 429    Must not be called with immediate_quit in effect (bad things might
 430    happen, say we got a signal in the middle of a memcpy to quit_return).
 431    This is an OK restriction; with very few exceptions immediate_quit can
 432    be replaced by judicious use of QUIT.  */
 433
 434 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 435    error() et al. could maintain a set of flags that indicate the
 436    current state of each of the longjmp buffers.  This would give the
 437    longjmp code the chance to detect a longjmp botch (before it gets
 438    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 439    code also randomly used a SET_TOP_LEVEL macro that directly
 440    initialized the longjmp buffers.  */
 441
 442 int
 443 catch_exceptions (struct ui_out *uiout,
 444                   catch_exceptions_ftype *func,
 445                   void *func_args,
 446                   return_mask mask)
 447 {
 448   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 449 }
 450
 451 int
 452 catch_exceptions_with_msg (struct ui_out *func_uiout,
 453                            catch_exceptions_ftype *func,
 454                            void *func_args,
 455                            char **gdberrmsg,
 456                            return_mask mask)
 457 {
 458   volatile struct gdb_exception exception;
 459   volatile int val = 0;
 460   struct ui_out *saved_uiout;
 461
 462   /* Save and override the global ``struct ui_out'' builder.  */
 463   saved_uiout = current_uiout;
 464   current_uiout = func_uiout;
 465
 466   TRY_CATCH (exception, RETURN_MASK_ALL)
 467     {
 468       val = (*func) (current_uiout, func_args);
 469     }
 470
 471   /* Restore the global builder.  */
 472   current_uiout = saved_uiout;
 473
 474   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 475     {
 476       /* The caller didn't request that the event be caught.
 477          Rethrow.  */
 478       throw_exception (exception);
 479     }
 480
 481   exception_print (gdb_stderr, exception);
 482   gdb_assert (val >= 0);
 483   gdb_assert (exception.reason <= 0);
 484   if (exception.reason < 0)
 485     {
 486       /* If caller wants a copy of the low-level error message, make
 487          one.  This is used in the case of a silent error whereby the
 488          caller may optionally want to issue the message.  */
 489       if (gdberrmsg != NULL)
 490         {
 491           if (exception.message != NULL)
 492             *gdberrmsg = xstrdup (exception.message);
 493           else
 494             *gdberrmsg = NULL;
 495         }
 496       return exception.reason;
 497     }
 498   return val;
 499 }
 500
 501 /* This function is superseded by catch_exceptions().  */
 502
 503 int
 504 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 505               return_mask mask)
 506 {
 507   volatile int val = 0;
 508   volatile struct gdb_exception exception;
 509   struct ui_out *saved_uiout;
 510
 511   /* Save the global ``struct ui_out'' builder.  */
 512   saved_uiout = current_uiout;
 513
 514   TRY_CATCH (exception, RETURN_MASK_ALL)
 515     {
 516       val = func (func_args);
 517     }
 518
 519   /* Restore the global builder.  */
 520   current_uiout = saved_uiout;
 521
 522   if (exception.reason < 0 && (mask & RETURN_MASK (exception.reason)) == 0)
 523     {
 524       /* The caller didn't request that the event be caught.
 525          Rethrow.  */
 526       throw_exception (exception);
 527     }
 528
 529   exception_fprintf (gdb_stderr, exception, "%s", errstring);
 530   if (exception.reason != 0)
 531     return 0;
 532   return val;
 533 }