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   struct ui_out *saved_uiout;
  77   struct cleanup *saved_cleanup_chain;
  78   /* Back link.  */
  79   struct catcher *prev;
  80 };
  81
  82 /* Where to go for throw_exception().  */
  83 static struct catcher *current_catcher;
  84
  85 static SIGJMP_BUF *
  86 catcher_init (struct ui_out *func_uiout,
  87               volatile struct exception *exception,
  88               return_mask mask)
  89 {
  90   struct catcher *new_catcher = XZALLOC (struct catcher);
  91
  92   /* Start with no exception, save it's address.  */
  93   exception->reason = 0;
  94   exception->error = NO_ERROR;
  95   exception->message = NULL;
  96   new_catcher->exception = exception;
  97
  98   new_catcher->mask = mask;
  99
 100   /* Override the global ``struct ui_out'' builder.  */
 101   new_catcher->saved_uiout = uiout;
 102   uiout = func_uiout;
 103
 104   /* Prevent error/quit during FUNC from calling cleanups established
 105      prior to here. */
 106   new_catcher->saved_cleanup_chain = save_cleanups ();
 107
 108   /* Push this new catcher on the top.  */
 109   new_catcher->prev = current_catcher;
 110   current_catcher = new_catcher;
 111   new_catcher->state = CATCHER_CREATED;
 112
 113   return &new_catcher->buf;
 114 }
 115
 116 static void
 117 catcher_pop (void)
 118 {
 119   struct catcher *old_catcher = current_catcher;
 120   current_catcher = old_catcher->prev;
 121
 122   /* Restore the cleanup chain, the error/quit messages, and the uiout
 123      builder, to their original states. */
 124
 125   restore_cleanups (old_catcher->saved_cleanup_chain);
 126
 127   uiout = old_catcher->saved_uiout;
 128
 129   xfree (old_catcher);
 130 }
 131
 132 /* Catcher state machine.  Returns non-zero if the m/c should be run
 133    again, zero if it should abort.  */
 134
 135 int
 136 catcher_state_machine (enum catcher_action action)
 137 {
 138   switch (current_catcher->state)
 139     {
 140     case CATCHER_CREATED:
 141       switch (action)
 142         {
 143         case CATCH_ITER:
 144           /* Allow the code to run the catcher.  */
 145           current_catcher->state = CATCHER_RUNNING;
 146           return 1;
 147         default:
 148           internal_error (__FILE__, __LINE__, "bad state");
 149         }
 150     case CATCHER_RUNNING:
 151       switch (action)
 152         {
 153         case CATCH_ITER:
 154           /* No error/quit has occured.  Just clean up.  */
 155           catcher_pop ();
 156           return 0;
 157         case CATCH_ITER_1:
 158           current_catcher->state = CATCHER_RUNNING_1;
 159           return 1;
 160         case CATCH_THROWING:
 161           current_catcher->state = CATCHER_ABORTING;
 162           /* See also throw_exception.  */
 163           return 1;
 164         default:
 165           internal_error (__FILE__, __LINE__, "bad switch");
 166         }
 167     case CATCHER_RUNNING_1:
 168       switch (action)
 169         {
 170         case CATCH_ITER:
 171           /* The did a "break" from the inner while loop.  */
 172           catcher_pop ();
 173           return 0;
 174         case CATCH_ITER_1:
 175           current_catcher->state = CATCHER_RUNNING;
 176           return 0;
 177         case CATCH_THROWING:
 178           current_catcher->state = CATCHER_ABORTING;
 179           /* See also throw_exception.  */
 180           return 1;
 181         default:
 182           internal_error (__FILE__, __LINE__, "bad switch");
 183         }
 184     case CATCHER_ABORTING:
 185       switch (action)
 186         {
 187         case CATCH_ITER:
 188           {
 189             struct exception exception = *current_catcher->exception;
 190             if (current_catcher->mask & RETURN_MASK (exception.reason))
 191               {
 192                 /* Exit normally if this catcher can handle this
 193                    exception.  The caller analyses the func return
 194                    values.  */
 195                 catcher_pop ();
 196                 return 0;
 197               }
 198             /* The caller didn't request that the event be caught,
 199                relay the event to the next containing
 200                catch_errors(). */
 201             catcher_pop ();
 202             throw_exception (exception);
 203           }
 204         default:
 205           internal_error (__FILE__, __LINE__, "bad state");
 206         }
 207     default:
 208       internal_error (__FILE__, __LINE__, "bad switch");
 209     }
 210 }
 211
 212 /* Return EXCEPTION to the nearest containing catch_errors().  */
 213
 214 NORETURN void
 215 throw_exception (struct exception exception)
 216 {
 217   quit_flag = 0;
 218   immediate_quit = 0;
 219
 220   /* Perhaps it would be cleaner to do this via the cleanup chain (not sure
 221      I can think of a reason why that is vital, though).  */
 222   bpstat_clear_actions (stop_bpstat);   /* Clear queued breakpoint commands */
 223
 224   disable_current_display ();
 225   do_cleanups (ALL_CLEANUPS);
 226   if (target_can_async_p () && !target_executing)
 227     do_exec_cleanups (ALL_CLEANUPS);
 228   if (sync_execution)
 229     do_exec_error_cleanups (ALL_CLEANUPS);
 230
 231   /* Jump to the containing catch_errors() call, communicating REASON
 232      to that call via setjmp's return value.  Note that REASON can't
 233      be zero, by definition in defs.h. */
 234   catcher_state_machine (CATCH_THROWING);
 235   *current_catcher->exception = exception;
 236   SIGLONGJMP (current_catcher->buf, exception.reason);
 237 }
 238
 239 static char *last_message;
 240
 241 NORETURN void
 242 throw_reason (enum return_reason reason)
 243 {
 244   struct exception exception;
 245   memset (&exception, 0, sizeof exception);
 246
 247   exception.reason = reason;
 248   switch (reason)
 249     {
 250     case RETURN_QUIT:
 251       break;
 252     case RETURN_ERROR:
 253       exception.error = GENERIC_ERROR;
 254       break;
 255     default:
 256       internal_error (__FILE__, __LINE__, "bad switch");
 257     }
 258
 259   throw_exception (exception);
 260 }
 261
 262 static void
 263 print_flush (void)
 264 {
 265   if (deprecated_error_begin_hook)
 266     deprecated_error_begin_hook ();
 267   target_terminal_ours ();
 268   wrap_here ("");               /* Force out any buffered output */
 269   gdb_flush (gdb_stdout);
 270   annotate_error_begin ();
 271 }
 272
 273 static void
 274 print_exception (struct ui_file *file, struct exception e)
 275 {
 276   /* KLUGE: cagney/2005-01-13: Write the string out one line at a time
 277      as that way the MI's behavior is preserved.  */
 278   const char *start;
 279   const char *end;
 280   for (start = e.message; start != NULL; start = end)
 281     {
 282       end = strchr (start, '\n');
 283       if (end == NULL)
 284         fputs_filtered (start, file);
 285       else
 286         {
 287           end++;
 288           ui_file_write (file, start, end - start);
 289         }
 290     }
 291   fprintf_filtered (file, "\n");
 292
 293   /* Now append the annotation.  */
 294   switch (e.reason)
 295     {
 296     case RETURN_QUIT:
 297       annotate_quit ();
 298       break;
 299     case RETURN_ERROR:
 300       /* Assume that these are all errors.  */
 301       annotate_error ();
 302       break;
 303     default:
 304       internal_error (__FILE__, __LINE__, _("Bad switch."));
 305     }
 306 }
 307
 308 void
 309 exception_print (struct ui_file *file, struct exception e)
 310 {
 311   if (e.reason < 0 && e.message != NULL)
 312     {
 313       print_flush ();
 314       print_exception (file, e);
 315     }
 316 }
 317
 318 void
 319 exception_fprintf (struct ui_file *file, struct exception e,
 320                    const char *prefix, ...)
 321 {
 322   if (e.reason < 0 && e.message != NULL)
 323     {
 324       va_list args;
 325
 326       print_flush ();
 327
 328       /* Print the prefix.  */
 329       va_start (args, prefix);
 330       vfprintf_filtered (file, prefix, args);
 331       va_end (args);
 332
 333       print_exception (file, e);
 334     }
 335 }
 336
 337 void
 338 print_any_exception (struct ui_file *file, const char *prefix,
 339                      struct exception e)
 340 {
 341   if (e.reason < 0 && e.message != NULL)
 342     {
 343       target_terminal_ours ();
 344       wrap_here ("");           /* Force out any buffered output */
 345       gdb_flush (gdb_stdout);
 346       annotate_error_begin ();
 347
 348       /* Print the prefix.  */
 349       if (prefix != NULL && prefix[0] != '\0')
 350         fputs_filtered (prefix, file);
 351       print_exception (file, e);
 352     }
 353 }
 354
 355 NORETURN static void
 356 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 357           va_list ap) ATTR_NORETURN;
 358 NORETURN static void
 359 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 360           va_list ap)
 361 {
 362   struct exception e;
 363   char *new_message;
 364
 365   /* Save the message.  Create the new message before deleting the
 366      old, the new message may include the old message text.  */
 367   new_message = xstrvprintf (fmt, ap);
 368   xfree (last_message);
 369   last_message = new_message;
 370
 371   /* Create the exception.  */
 372   e.reason = reason;
 373   e.error = error;
 374   e.message = last_message;
 375
 376   /* Throw the exception.  */
 377   throw_exception (e);
 378 }
 379
 380 NORETURN void
 381 throw_verror (enum errors error, const char *fmt, va_list ap)
 382 {
 383   throw_it (RETURN_ERROR, error, fmt, ap);
 384 }
 385
 386 NORETURN void
 387 throw_vfatal (const char *fmt, va_list ap)
 388 {
 389   throw_it (RETURN_QUIT, NO_ERROR, fmt, ap);
 390 }
 391
 392 NORETURN void
 393 throw_error (enum errors error, const char *fmt, ...)
 394 {
 395   va_list args;
 396   va_start (args, fmt);
 397   throw_it (RETURN_ERROR, error, fmt, args);
 398   va_end (args);
 399 }
 400
 401 /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
 402    errors.  Set FUNC_CAUGHT to an ``enum return_reason'' if the
 403    function is aborted (using throw_exception() or zero if the
 404    function returns normally.  Set FUNC_VAL to the value returned by
 405    the function or 0 if the function was aborted.
 406
 407    Must not be called with immediate_quit in effect (bad things might
 408    happen, say we got a signal in the middle of a memcpy to quit_return).
 409    This is an OK restriction; with very few exceptions immediate_quit can
 410    be replaced by judicious use of QUIT.
 411
 412    MASK specifies what to catch; it is normally set to
 413    RETURN_MASK_ALL, if for no other reason than that the code which
 414    calls catch_errors might not be set up to deal with a quit which
 415    isn't caught.  But if the code can deal with it, it generally
 416    should be RETURN_MASK_ERROR, unless for some reason it is more
 417    useful to abort only the portion of the operation inside the
 418    catch_errors.  Note that quit should return to the command line
 419    fairly quickly, even if some further processing is being done.  */
 420
 421 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 422    error() et.al. could maintain a set of flags that indicate the the
 423    current state of each of the longjmp buffers.  This would give the
 424    longjmp code the chance to detect a longjmp botch (before it gets
 425    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 426    code also randomly used a SET_TOP_LEVEL macro that directly
 427    initialize the longjmp buffers. */
 428
 429 /* MAYBE: cagney/1999-11-05: Should the catch_errors and cleanups code
 430    be consolidated into a single file instead of being distributed
 431    between utils.c and top.c? */
 432
 433 int
 434 catch_exceptions (struct ui_out *uiout,
 435                   catch_exceptions_ftype *func,
 436                   void *func_args,
 437                   return_mask mask)
 438 {
 439   return catch_exceptions_with_msg (uiout, func, func_args, NULL, mask);
 440 }
 441
 442 struct exception
 443 catch_exception (struct ui_out *uiout,
 444                  catch_exception_ftype *func,
 445                  void *func_args,
 446                  return_mask mask)
 447 {
 448   volatile struct exception exception;
 449   SIGJMP_BUF *catch;
 450   catch = catcher_init (uiout, &exception, mask);
 451   for (SIGSETJMP ((*catch));
 452        catcher_state_machine (CATCH_ITER);)
 453     (*func) (uiout, func_args);
 454   return exception;
 455 }
 456
 457 int
 458 catch_exceptions_with_msg (struct ui_out *uiout,
 459                            catch_exceptions_ftype *func,
 460                            void *func_args,
 461                            char **gdberrmsg,
 462                            return_mask mask)
 463 {
 464   volatile struct exception exception;
 465   volatile int val = 0;
 466   SIGJMP_BUF *catch = catcher_init (uiout, &exception, mask);
 467   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 468     val = (*func) (uiout, func_args);
 469   print_any_exception (gdb_stderr, NULL, exception);
 470   gdb_assert (val >= 0);
 471   gdb_assert (exception.reason <= 0);
 472   if (exception.reason < 0)
 473     {
 474       /* If caller wants a copy of the low-level error message, make
 475          one.  This is used in the case of a silent error whereby the
 476          caller may optionally want to issue the message.  */
 477       if (gdberrmsg != NULL)
 478         {
 479           if (exception.message != NULL)
 480             *gdberrmsg = xstrdup (exception.message);
 481           else
 482             *gdberrmsg = NULL;
 483         }
 484       return exception.reason;
 485     }
 486   return val;
 487 }
 488
 489 int
 490 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 491               return_mask mask)
 492 {
 493   volatile int val = 0;
 494   volatile struct exception exception;
 495   SIGJMP_BUF *catch = catcher_init (uiout, &exception, mask);
 496   /* This illustrates how it is possible to nest the mechanism and
 497      hence catch "break".  Of course this doesn't address the need to
 498      also catch "return".  */
 499   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 500     val = func (func_args);
 501   print_any_exception (gdb_stderr, errstring, exception);
 502   if (exception.reason != 0)
 503     return 0;
 504   return val;
 505 }
 506
 507 int
 508 catch_command_errors (catch_command_errors_ftype * command,
 509                       char *arg, int from_tty, return_mask mask)
 510 {
 511   volatile struct exception e;
 512   SIGJMP_BUF *catch = catcher_init (uiout, &e, mask);
 513   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 514     command (arg, from_tty);
 515   print_any_exception (gdb_stderr, NULL, e);
 516   if (e.reason < 0)
 517     return 0;
 518   return 1;
 519 }