gdb/common/common-exceptions.c

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2015 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 "common-defs.h"
  21 #include "common-exceptions.h"
  22
  23 /* Possible catcher states.  */
  24 enum catcher_state {
  25   /* Initial state, a new catcher has just been created.  */
  26   CATCHER_CREATED,
  27   /* The catch code is running.  */
  28   CATCHER_RUNNING,
  29   CATCHER_RUNNING_1,
  30   /* The catch code threw an exception.  */
  31   CATCHER_ABORTING
  32 };
  33
  34 /* Possible catcher actions.  */
  35 enum catcher_action {
  36   CATCH_ITER,
  37   CATCH_ITER_1,
  38   CATCH_THROWING
  39 };
  40
  41 struct catcher
  42 {
  43   enum catcher_state state;
  44   /* Jump buffer pointing back at the exception handler.  */
  45   SIGJMP_BUF buf;
  46   /* Status buffer belonging to the exception handler.  */
  47   volatile struct gdb_exception *exception;
  48   /* Saved/current state.  */
  49   int mask;
  50   struct cleanup *saved_cleanup_chain;
  51   /* Back link.  */
  52   struct catcher *prev;
  53 };
  54
  55 /* Where to go for throw_exception().  */
  56 static struct catcher *current_catcher;
  57
  58 /* Return length of current_catcher list.  */
  59
  60 static int
  61 catcher_list_size (void)
  62 {
  63   int size;
  64   struct catcher *catcher;
  65
  66   for (size = 0, catcher = current_catcher;
  67        catcher != NULL;
  68        catcher = catcher->prev)
  69     ++size;
  70
  71   return size;
  72 }
  73
  74 SIGJMP_BUF *
  75 exceptions_state_mc_init (volatile struct gdb_exception *exception,
  76                           return_mask mask)
  77 {
  78   struct catcher *new_catcher = XCNEW (struct catcher);
  79
  80   /* Start with no exception, save it's address.  */
  81   exception->reason = 0;
  82   exception->error = GDB_NO_ERROR;
  83   exception->message = NULL;
  84   new_catcher->exception = exception;
  85
  86   new_catcher->mask = mask;
  87
  88   /* Prevent error/quit during FUNC from calling cleanups established
  89      prior to here.  */
  90   new_catcher->saved_cleanup_chain = save_cleanups ();
  91
  92   /* Push this new catcher on the top.  */
  93   new_catcher->prev = current_catcher;
  94   current_catcher = new_catcher;
  95   new_catcher->state = CATCHER_CREATED;
  96
  97   return &new_catcher->buf;
  98 }
  99
 100 static void
 101 catcher_pop (void)
 102 {
 103   struct catcher *old_catcher = current_catcher;
 104
 105   current_catcher = old_catcher->prev;
 106
 107   /* Restore the cleanup chain, the error/quit messages, and the uiout
 108      builder, to their original states.  */
 109
 110   restore_cleanups (old_catcher->saved_cleanup_chain);
 111
 112   xfree (old_catcher);
 113 }
 114
 115 /* Catcher state machine.  Returns non-zero if the m/c should be run
 116    again, zero if it should abort.  */
 117
 118 static int
 119 exceptions_state_mc (enum catcher_action action)
 120 {
 121   switch (current_catcher->state)
 122     {
 123     case CATCHER_CREATED:
 124       switch (action)
 125         {
 126         case CATCH_ITER:
 127           /* Allow the code to run the catcher.  */
 128           current_catcher->state = CATCHER_RUNNING;
 129           return 1;
 130         default:
 131           internal_error (__FILE__, __LINE__, _("bad state"));
 132         }
 133     case CATCHER_RUNNING:
 134       switch (action)
 135         {
 136         case CATCH_ITER:
 137           /* No error/quit has occured.  Just clean up.  */
 138           catcher_pop ();
 139           return 0;
 140         case CATCH_ITER_1:
 141           current_catcher->state = CATCHER_RUNNING_1;
 142           return 1;
 143         case CATCH_THROWING:
 144           current_catcher->state = CATCHER_ABORTING;
 145           /* See also throw_exception.  */
 146           return 1;
 147         default:
 148           internal_error (__FILE__, __LINE__, _("bad switch"));
 149         }
 150     case CATCHER_RUNNING_1:
 151       switch (action)
 152         {
 153         case CATCH_ITER:
 154           /* The did a "break" from the inner while loop.  */
 155           catcher_pop ();
 156           return 0;
 157         case CATCH_ITER_1:
 158           current_catcher->state = CATCHER_RUNNING;
 159           return 0;
 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_ABORTING:
 168       switch (action)
 169         {
 170         case CATCH_ITER:
 171           {
 172             struct gdb_exception exception = *current_catcher->exception;
 173
 174             if (current_catcher->mask & RETURN_MASK (exception.reason))
 175               {
 176                 /* Exit normally if this catcher can handle this
 177                    exception.  The caller analyses the func return
 178                    values.  */
 179                 catcher_pop ();
 180                 return 0;
 181               }
 182             /* The caller didn't request that the event be caught,
 183                relay the event to the next containing
 184                catch_errors().  */
 185             catcher_pop ();
 186             throw_exception (exception);
 187           }
 188         default:
 189           internal_error (__FILE__, __LINE__, _("bad state"));
 190         }
 191     default:
 192       internal_error (__FILE__, __LINE__, _("bad switch"));
 193     }
 194 }
 195
 196 int
 197 exceptions_state_mc_action_iter (void)
 198 {
 199   return exceptions_state_mc (CATCH_ITER);
 200 }
 201
 202 int
 203 exceptions_state_mc_action_iter_1 (void)
 204 {
 205   return exceptions_state_mc (CATCH_ITER_1);
 206 }
 207
 208 /* Return EXCEPTION to the nearest containing catch_errors().  */
 209
 210 void
 211 throw_exception (struct gdb_exception exception)
 212 {
 213   prepare_to_throw_exception ();
 214
 215   do_cleanups (all_cleanups ());
 216
 217   /* Jump to the containing catch_errors() call, communicating REASON
 218      to that call via setjmp's return value.  Note that REASON can't
 219      be zero, by definition in defs.h.  */
 220   exceptions_state_mc (CATCH_THROWING);
 221   *current_catcher->exception = exception;
 222   SIGLONGJMP (current_catcher->buf, exception.reason);
 223 }
 224
 225 /* A stack of exception messages.
 226    This is needed to handle nested calls to throw_it: we don't want to
 227    xfree space for a message before it's used.
 228    This can happen if we throw an exception during a cleanup:
 229    An outer TRY_CATCH may have an exception message it wants to print,
 230    but while doing cleanups further calls to throw_it are made.
 231
 232    This is indexed by the size of the current_catcher list.
 233    It is a dynamically allocated array so that we don't care how deeply
 234    GDB nests its TRY_CATCHs.  */
 235 static char **exception_messages;
 236
 237 /* The number of currently allocated entries in exception_messages.  */
 238 static int exception_messages_size;
 239
 240 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 241 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 242           va_list ap)
 243 {
 244   struct gdb_exception e;
 245   char *new_message;
 246   int depth = catcher_list_size ();
 247
 248   gdb_assert (depth > 0);
 249
 250   /* Note: The new message may use an old message's text.  */
 251   new_message = xstrvprintf (fmt, ap);
 252
 253   if (depth > exception_messages_size)
 254     {
 255       int old_size = exception_messages_size;
 256
 257       exception_messages_size = depth + 10;
 258       exception_messages = (char **) xrealloc (exception_messages,
 259                                                exception_messages_size
 260                                                * sizeof (char *));
 261       memset (exception_messages + old_size, 0,
 262               (exception_messages_size - old_size) * sizeof (char *));
 263     }
 264
 265   xfree (exception_messages[depth - 1]);
 266   exception_messages[depth - 1] = new_message;
 267
 268   /* Create the exception.  */
 269   e.reason = reason;
 270   e.error = error;
 271   e.message = new_message;
 272
 273   /* Throw the exception.  */
 274   throw_exception (e);
 275 }
 276
 277 void
 278 throw_verror (enum errors error, const char *fmt, va_list ap)
 279 {
 280   throw_it (RETURN_ERROR, error, fmt, ap);
 281 }
 282
 283 void
 284 throw_vquit (const char *fmt, va_list ap)
 285 {
 286   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 287 }
 288
 289 void
 290 throw_error (enum errors error, const char *fmt, ...)
 291 {
 292   va_list args;
 293
 294   va_start (args, fmt);
 295   throw_verror (error, fmt, args);
 296   va_end (args);
 297 }
 298
 299 void
 300 throw_quit (const char *fmt, ...)
 301 {
 302   va_list args;
 303
 304   va_start (args, fmt);
 305   throw_vquit (fmt, args);
 306   va_end (args);
 307 }