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 Free Software
   5    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 that 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   if (annotation_level > 1)
 246     switch (exception.reason)
 247       {
 248       case RETURN_QUIT:
 249         annotate_quit ();
 250         break;
 251       case RETURN_ERROR:
 252         /* Assume that these are all errors.  */
 253         annotate_error ();
 254         break;
 255       default:
 256         internal_error (__FILE__, __LINE__, "Bad switch.");
 257       }
 258
 259   /* Jump to the containing catch_errors() call, communicating REASON
 260      to that call via setjmp's return value.  Note that REASON can't
 261      be zero, by definition in defs.h. */
 262   catcher_state_machine (CATCH_THROWING);
 263   *current_catcher->exception = exception;
 264   SIGLONGJMP (current_catcher->buf, exception.reason);
 265 }
 266
 267 NORETURN void
 268 throw_reason (enum return_reason reason)
 269 {
 270   struct exception exception;
 271   memset (&exception, 0, sizeof exception);
 272
 273   exception.reason = reason;
 274   switch (reason)
 275     {
 276     case RETURN_QUIT:
 277       break;
 278     case RETURN_ERROR:
 279       exception.error = GENERIC_ERROR;
 280       exception.message = error_last_message ();
 281       break;
 282     default:
 283       internal_error (__FILE__, __LINE__, "bad switch");
 284     }
 285
 286   throw_exception (exception);
 287 }
 288
 289 /* Call FUNC() with args FUNC_UIOUT and FUNC_ARGS, catching any
 290    errors.  Set FUNC_CAUGHT to an ``enum return_reason'' if the
 291    function is aborted (using throw_exception() or zero if the
 292    function returns normally.  Set FUNC_VAL to the value returned by
 293    the function or 0 if the function was aborted.
 294
 295    Must not be called with immediate_quit in effect (bad things might
 296    happen, say we got a signal in the middle of a memcpy to quit_return).
 297    This is an OK restriction; with very few exceptions immediate_quit can
 298    be replaced by judicious use of QUIT.
 299
 300    MASK specifies what to catch; it is normally set to
 301    RETURN_MASK_ALL, if for no other reason than that the code which
 302    calls catch_errors might not be set up to deal with a quit which
 303    isn't caught.  But if the code can deal with it, it generally
 304    should be RETURN_MASK_ERROR, unless for some reason it is more
 305    useful to abort only the portion of the operation inside the
 306    catch_errors.  Note that quit should return to the command line
 307    fairly quickly, even if some further processing is being done.  */
 308
 309 /* MAYBE: cagney/1999-11-05: catch_errors() in conjunction with
 310    error() et.al. could maintain a set of flags that indicate the the
 311    current state of each of the longjmp buffers.  This would give the
 312    longjmp code the chance to detect a longjmp botch (before it gets
 313    to longjmperror()).  Prior to 1999-11-05 this wasn't possible as
 314    code also randomly used a SET_TOP_LEVEL macro that directly
 315    initialize the longjmp buffers. */
 316
 317 /* MAYBE: cagney/1999-11-05: Should the catch_errors and cleanups code
 318    be consolidated into a single file instead of being distributed
 319    between utils.c and top.c? */
 320
 321 int
 322 catch_exceptions (struct ui_out *uiout,
 323                   catch_exceptions_ftype *func,
 324                   void *func_args,
 325                   char *errstring,
 326                   return_mask mask)
 327 {
 328   return catch_exceptions_with_msg (uiout, func, func_args, errstring,
 329                                     NULL, mask);
 330 }
 331
 332 struct exception
 333 catch_exception (struct ui_out *uiout,
 334                  catch_exception_ftype *func,
 335                  void *func_args,
 336                  return_mask mask)
 337 {
 338   volatile struct exception exception;
 339   SIGJMP_BUF *catch;
 340   catch = catcher_init (uiout, NULL, &exception, mask);
 341   for (SIGSETJMP ((*catch));
 342        catcher_state_machine (CATCH_ITER);)
 343     (*func) (uiout, func_args);
 344   return exception;
 345 }
 346
 347 int
 348 catch_exceptions_with_msg (struct ui_out *uiout,
 349                            catch_exceptions_ftype *func,
 350                            void *func_args,
 351                            char *errstring,
 352                            char **gdberrmsg,
 353                            return_mask mask)
 354 {
 355   volatile struct exception exception;
 356   volatile int val = 0;
 357   SIGJMP_BUF *catch = catcher_init (uiout, errstring, &exception, mask);
 358   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 359     val = (*func) (uiout, func_args);
 360   gdb_assert (val >= 0);
 361   gdb_assert (exception.reason <= 0);
 362   if (exception.reason < 0)
 363     {
 364       /* If caller wants a copy of the low-level error message, make
 365          one.  This is used in the case of a silent error whereby the
 366          caller may optionally want to issue the message.  */
 367       if (gdberrmsg != NULL)
 368         *gdberrmsg = exception.message;
 369       return exception.reason;
 370     }
 371   return val;
 372 }
 373
 374 int
 375 catch_errors (catch_errors_ftype *func, void *func_args, char *errstring,
 376               return_mask mask)
 377 {
 378   volatile int val = 0;
 379   volatile struct exception exception;
 380   SIGJMP_BUF *catch = catcher_init (uiout, errstring, &exception, mask);
 381   /* This illustrates how it is possible to nest the mechanism and
 382      hence catch "break".  Of course this doesn't address the need to
 383      also catch "return".  */
 384   for (SIGSETJMP ((*catch)); catcher_state_machine (CATCH_ITER);)
 385     val = func (func_args);
 386   if (exception.reason != 0)
 387     return 0;
 388   return val;
 389 }
 390
 391 struct captured_command_args
 392   {
 393     catch_command_errors_ftype *command;
 394     char *arg;
 395     int from_tty;
 396   };
 397
 398 static int
 399 do_captured_command (void *data)
 400 {
 401   struct captured_command_args *context = data;
 402   context->command (context->arg, context->from_tty);
 403   /* FIXME: cagney/1999-11-07: Technically this do_cleanups() call
 404      isn't needed.  Instead an assertion check could be made that
 405      simply confirmed that the called function correctly cleaned up
 406      after itself.  Unfortunately, old code (prior to 1999-11-04) in
 407      main.c was calling SET_TOP_LEVEL(), calling the command function,
 408      and then *always* calling do_cleanups().  For the moment we
 409      remain ``bug compatible'' with that old code..  */
 410   do_cleanups (ALL_CLEANUPS);
 411   return 1;
 412 }
 413
 414 int
 415 catch_command_errors (catch_command_errors_ftype * command,
 416                       char *arg, int from_tty, return_mask mask)
 417 {
 418   struct captured_command_args args;
 419   args.command = command;
 420   args.arg = arg;
 421   args.from_tty = from_tty;
 422   return catch_errors (do_captured_command, &args, "", mask);
 423 }