gdb/exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright 1986, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   4    1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free
   5    Software Foundation, Inc.
   6
   7    This file is part of GDB.
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 2 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program; if not, write to the Free Software
  21    Foundation, Inc., 59 Temple Place - Suite 330,
  22    Boston, MA 02111-1307, USA.  */
  23
  24 #include "defs.h"
  25 #include "exceptions.h"
  26 #include <setjmp.h>
  27 #include "breakpoint.h"
  28 #include "target.h"
  29 #include "inferior.h"
  30 #include "annotate.h"
  31 #include "ui-out.h"
  32 #include "gdb_assert.h"
  33 #include "gdb_string.h"
  34
  35 const struct exception exception_none = { 0, NO_ERROR, NULL };
  36
  37 /* One should use catch_errors rather than manipulating these
  38    directly.  */
  39 #if defined(HAVE_SIGSETJMP)
  40 #define SIGJMP_BUF              sigjmp_buf
  41 #define SIGSETJMP(buf)          sigsetjmp((buf), 1)
  42 #define SIGLONGJMP(buf,val)     siglongjmp((buf), (val))
  43 #else
  44 #define SIGJMP_BUF              jmp_buf
  45 #define SIGSETJMP(buf)          setjmp(buf)
  46 #define SIGLONGJMP(buf,val)     longjmp((buf), (val))
  47 #endif
  48
  49 /* Possible catcher states.  */
  50 enum catcher_state {
  51   /* Initial state, a new catcher has just been created.  */
  52   CATCHER_CREATED,
  53   /* The catch code is running.  */
  54   CATCHER_RUNNING,
  55   CATCHER_RUNNING_1,
  56   /* The catch code threw an exception.  */
  57   CATCHER_ABORTING
  58 };
  59
  60 /* Possible catcher actions.  */
  61 enum catcher_action {
  62   CATCH_ITER,
  63   CATCH_ITER_1,
  64   CATCH_THROWING
  65 };
  66
  67 struct catcher
  68 {
  69   enum catcher_state state;
  70   /* Jump buffer pointing back at the exception handler.  */
  71   SIGJMP_BUF buf;
  72   /* Status buffer belonging to the exception handler.  */
  73   volatile struct exception *exception;
  74   /* Saved/current state.  */
  75   int mask;
  76   char *saved_error_pre_print;
  77   char *saved_quit_pre_print;
  78   struct ui_out *saved_uiout;
  79   struct cleanup *saved_cleanup_chain;
  80   /* Back link.  */
  81   struct catcher *prev;
  82 };
  83
  84 /* Where to go for throw_exception().  */
  85 static struct catcher *current_catcher;
  86
  87 static SIGJMP_BUF *
  88 catcher_init (struct ui_out *func_uiout,
  89               char *errstring,
  90               volatile struct exception *exception,
  91               return_mask mask)
  92 {
  93   struct catcher *new_catcher = XZALLOC (struct catcher);
  94
  95   /* Start with no exception, save it's address.  */
  96   exception->reason = 0;
  97   exception->error = NO_ERROR;
  98   exception->message = NULL;
  99   new_catcher->exception = exception;
 100
 101   new_catcher->mask = mask;
 102
 103   /* Override error/quit messages during FUNC. */
 104   new_catcher->saved_error_pre_print = error_pre_print;
 105   new_catcher->saved_quit_pre_print = quit_pre_print;
 106   if (mask & RETURN_MASK_ERROR)
 107     error_pre_print = errstring;
 108   if (mask & RETURN_MASK_QUIT)
 109     quit_pre_print = errstring;
 110
 111   /* Override the global ``struct ui_out'' builder.  */
 112   new_catcher->saved_uiout = uiout;
 113   uiout = func_uiout;
 114
 115   /* Prevent error/quit during FUNC from calling cleanups established
 116      prior to here. */
 117   new_catcher->saved_cleanup_chain = save_cleanups ();
 118
 119   /* Push this new catcher on the top.  */
 120   new_catcher->prev = current_catcher;
 121   current_catcher = new_catcher;
 122   new_catcher->state = CATCHER_CREATED;
 123
 124   return &new_catcher->buf;
 125 }
 126
 127 static void
 128 catcher_pop (void)
 129 {
 130   struct catcher *old_catcher = current_catcher;
 131   current_catcher = old_catcher->prev;
 132
 133   /* Restore the cleanup chain, the error/quit messages, and the uiout
 134      builder, to their original states. */
 135
 136   restore_cleanups (old_catcher->saved_cleanup_chain);
 137
 138   uiout = old_catcher->saved_uiout;
 139
 140   quit_pre_print = old_catcher->saved_quit_pre_print;
 141   error_pre_print = old_catcher->saved_error_pre_print;
 142
 143   xfree (old_catcher);
 144 }
 145
 146 /* Catcher state machine.  Returns non-zero if the m/c should be run
 147    again, zero if it should abort.  */
 148
 149 int
 150 catcher_state_machine (enum catcher_action action)
 151 {
 152   switch (current_catcher->state)
 153     {
 154     case CATCHER_CREATED:
 155       switch (action)
 156         {
 157         case CATCH_ITER:
 158           /* Allow the code to run the catcher.  */
 159           current_catcher->state = CATCHER_RUNNING;
 160           return 1;
 161         default:
 162           internal_error (__FILE__, __LINE__, "bad state");
 163         }
 164     case CATCHER_RUNNING:
 165       switch (action)
 166         {
 167         case CATCH_ITER:
 168           /* No error/quit has occured.  Just clean up.  */
 169           catcher_pop ();
 170           return 0;
 171         case CATCH_ITER_1:
 172           current_catcher->state = CATCHER_RUNNING_1;
 173           return 1;
 174         case CATCH_THROWING:
 175           current_catcher->state = CATCHER_ABORTING;
 176           /* See also throw_exception.  */
 177           return 1;
 178         default:
 179           internal_error (__FILE__, __LINE__, "bad switch");
 180         }
 181     case CATCHER_RUNNING_1:
 182       switch (action)
 183         {
 184         case CATCH_ITER:
 185           /* The did a "break" from the inner while loop.  */
 186           catcher_pop ();
 187           return 0;
 188         case CATCH_ITER_1:
 189           current_catcher->state = CATCHER_RUNNING;
 190           return 0;
 191         case CATCH_THROWING:
 192           current_catcher->state = CATCHER_ABORTING;
 193           /* See also throw_exception.  */
 194           return 1;
 195         default:
 196           internal_error (__FILE__, __LINE__, "bad switch");
 197         }
 198     case CATCHER_ABORTING:
 199       switch (action)
 200         {
 201         case CATCH_ITER:
 202           {
 203             struct exception exception = *current_catcher->exception;
 204             if (current_catcher->mask & RETURN_MASK (exception.reason))
 205               {
 206                 /* Exit normally if this catcher can handle this
 207                    exception.  The caller analyses the func return
 208                    values.  */
 209                 catcher_pop ();
 210                 return 0;
 211               }
 212             /* The caller didn't request that the event be caught,
 213                relay the event to the next containing
 214                catch_errors(). */
 215             catcher_pop ();
 216             throw_exception (exception);
 217           }
 218         default:
 219           internal_error (__FILE__, __LINE__, "bad state");
 220         }
 221     default:
 222       internal_error (__FILE__, __LINE__, "bad switch");
 223     }
 224 }
 225
 226 /* Return EXCEPTION to the nearest containing catch_errors().  */
 227
 228 NORETURN void
 229 throw_exception (struct exception exception)
 230 {
 231   quit_flag = 0;
 232   immediate_quit = 0;
 233
 234   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 235      I can think of a reason why that is vital, though).  */
 236   bpstat_clear_actions (stop_bpstat);   /* Clear queued breakpoint commands */
 237
 238   disable_current_display ();
 239   do_cleanups (ALL_CLEANUPS);
 240   if (target_can_async_p () && !target_executing)
 241     do_exec_cleanups (ALL_CLEANUPS);
 242   if (sync_execution)
 243     do_exec_error_cleanups (ALL_CLEANUPS);
 244
 245   /* Jump to the containing catch_errors() call, communicating REASON
 246      to that call via setjmp's return value.  Note that REASON can't
 247      be zero, by definition in defs.h. */
 248   catcher_state_machine (CATCH_THROWING);
 249   *current_catcher->exception = exception;
 250   SIGLONGJMP (current_catcher->buf, exception.reason);
 251 }
 252
 253 static char *last_message;
 254
 255 NORETURN void
 256 throw_reason (enum return_reason reason)
 257 {
 258   struct exception exception;
 259   memset (&exception, 0, sizeof exception);
 260
 261   exception.reason = reason;
 262   switch (reason)
 263     {
 264     case RETURN_QUIT:
 265       break;
 266     case RETURN_ERROR:
 267       exception.error = GENERIC_ERROR;
 268       break;
 269     default:
 270       internal_error (__FILE__, __LINE__, "bad switch");
 271     }
 272
 273   throw_exception (exception);
 274 }
 275
 276 static void
 277 print_flush (void)
 278 {
 279   if (deprecated_error_begin_hook)
 280     deprecated_error_begin_hook ();
 281   target_terminal_ours ();
 282   wrap_here ("");               /* Force out any buffered output */
 283   gdb_flush (gdb_stdout);
 284   annotate_error_begin ();
 285 }
 286
 287 static void
 288 print_exception (struct ui_file *file, struct exception e)
 289 {
 290   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 291      as that way the MI's behavior is preserved.  */
 292   const char *start;
 293   const char *end;
 294   for (start = e.message; start != NULL; start = end)
 295     {
 296       end = strchr (start, '\n');
 297       if (end == NULL)
 298         fputs_filtered (start, file);
 299       else
 300         {
 301           end++;
 302           ui_file_write (file, start, end - start);
 303         }
 304     }
 305   fprintf_filtered (file, "\n");
 306
 307   /* Now append the annotation.  */
 308   switch (e.reason)
 309     {
 310     case RETURN_QUIT:
 311       annotate_quit ();
 312       break;
 313     case RETURN_ERROR:
 314       /* Assume that these are all errors.  */
 315       annotate_error ();
 316       break;
 317     default:
 318       internal_error (__FILE__, __LINE__, _("Bad switch."));
 319     }
 320 }
 321
 322 void
 323 exception_print (struct ui_file *file, struct exception e)
 324 {
 325   if (e.reason < 0 && e.message != NULL)
 326     {
 327       print_flush ();
 328       print_exception (file, e);
 329     }
 330 }
 331
 332 void
 333 exception_fprintf (struct ui_file *file, struct exception e,
 334                    const char *prefix, ...)
 335 {
 336   if (e.reason < 0 && e.message != NULL)
 337     {
 338       va_list args;
 339
 340       print_flush ();
 341
 342       /* Print the prefix.  */
 343       va_start (args, prefix);
 344       vfprintf_filtered (file, prefix, args);
 345       va_end (args);
 346
 347       print_exception (file, e);
 348     }
 349 }
 350
 351 void
 352 print_any_exception (struct ui_file *file, const char *prefix,
 353                      struct exception e)
 354 {
 355   if (e.reason < 0 && e.message != NULL)
 356     {
 357       target_terminal_ours ();
 358       wrap_here ("");           /* Force out any buffered output */
 359       gdb_flush (gdb_stdout);
 360       annotate_error_begin ();
 361
 362       /* Print the prefix.  */
 363       if (prefix != NULL && prefix[0] != '\0')
 364         fputs_filtered (prefix, file);
 365       print_exception (file, e);
 366     }
 367 }
 368
 369 NORETURN static void
 370 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 371           va_list ap) ATTR_NORETURN;
 372 NORETURN static void
 373 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 374           va_list ap)
 375 {
 376   struct exception e;
 377
 378   /* Save the message.  */
 379   xfree (last_message);
 380   last_message = xstrvprintf (fmt, ap);
 381
 382   /* Create the exception.  */
 383   e.reason = reason;
 384   e.error = error;
 385   e.message = last_message;
 386
 387   /* Throw the exception.  */
 388   throw_exception (e);
 389 }
 390
 391 NORETURN void
 392 throw_verror (enum errors error, const char *fmt, va_list ap)
 393 {
 394   throw_it (RETURN_ERROR, error, fmt, ap);
 395 }
 396
 397 NORETURN void
 398 throw_vfatal (const char *fmt, va_list ap)
 399 {
 400   throw_it (RETURN_QUIT, NO_ERROR, fmt, ap);
 401 }
 402
 403 NORETURN void
 404 throw_error (enum errors error, const char *fmt, ...)
 405 {
 406   va_list args;
 407   va_start (args, fmt);
 408   throw_it (RETURN_ERROR, error, fmt, args);
 409   va_end (args);
 410 }
 411
 412 /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
 413    errors.  Set FUNC_CAUGHT to an ``enum return_reason'' if the
 414    function is aborted (using throw_exception() or zero if the
 415    function returns normally.  Set FUNC_VAL to the value returned by
 416    the function or 0 if the function was aborted.
 417
 418    Must not be called with immediate_quit in effect (bad things might
 419    happen, say we got a signal in the middle of a memcpy to quit_return).
 420    This is an OK restriction; with very few exceptions immediate_quit can
 421    be replaced by judicious use of QUIT.
 422
 423    MASK specifies what to catch; it is normally set to
 424    RETURN_MASK_ALL, if for no other reason than that the code which
 425    calls catch_errors might not be set up to deal with a quit which
 426    isn't caught.  But if the code can deal with it, it generally
 427    should be RETURN_MASK_ERROR, unless for some reason it is more
 428    useful to abort only the portion of the operation inside the
 429    catch_errors.  Note that quit should return to the command line
 430    fairly quickly, even if some further processing is being done.  */
 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 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    initialize the longjmp buffers. */
 439
 440 /* MAYBE: cagney/1999-11-05: Should the catch_errors and cleanups code
 441    be consolidated into a single file instead of being distributed
 442    between utils.c and top.c? */
 443
 444 int
 445 catch_exceptions (struct ui_out *uiout,
 446                   catch_exceptions_ftype *func,
 447                   void *func_args,
 448                   return_mask mask)
 449 {
 450   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 451 }
 452
 453 struct exception
 454 catch_exception (struct ui_out *uiout,
 455                  catch_exception_ftype *func,
 456                  void *func_args,
 457                  return_mask mask)
 458 {
 459   volatile struct exception exception;
 460   SIGJMP_BUF *catch;
 461   catch = catcher_init (uiout, NULL, &exception, mask);
 462   for (SIGSETJMP ((*catch));
 463        catcher_state_machine (CATCH_ITER);)
 464     (*func) (uiout, func_args);
 465   return exception;
 466 }
 467
 468 int
 469 catch_exceptions_with_msg (struct ui_out *uiout,
 470                            catch_exceptions_ftype *func,
 471                            void *func_args,
 472                            char **gdberrmsg,
 473                            return_mask mask)
 474 {
 475   volatile struct exception exception;
 476   volatile int val = 0;
 477   SIGJMP_BUF *catch = catcher_init (uiout, NULL, &exception, mask);
 478   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 479     val = (*func) (uiout, func_args);
 480   print_any_exception (gdb_stderr, NULL, 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 int
 501 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 502               return_mask mask)
 503 {
 504   volatile int val = 0;
 505   volatile struct exception exception;
 506   SIGJMP_BUF *catch = catcher_init (uiout, errstring, &exception, mask);
 507   /* This illustrates how it is possible to nest the mechanism and
 508      hence catch "break".  Of course this doesn't address the need to
 509      also catch "return".  */
 510   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 511     val = func (func_args);
 512   print_any_exception (gdb_stderr, errstring, exception);
 513   if (exception.reason != 0)
 514     return 0;
 515   return val;
 516 }
 517
 518 int
 519 catch_command_errors (catch_command_errors_ftype * command,
 520                       char *arg, int from_tty, return_mask mask)
 521 {
 522   volatile struct exception e;
 523   SIGJMP_BUF *catch = catcher_init (uiout, NULL, &e, mask);
 524   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 525     command (arg, from_tty);
 526   print_any_exception (gdb_stderr, NULL, e);
 527   if (e.reason < 0)
 528     return 0;
 529   return 1;
 530 }