gdbsupport/common-exceptions.cc

   1 /* Exception (throw catch) mechanism, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2020 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 #include <forward_list>
  23
  24 /* Possible catcher states.  */
  25 enum catcher_state {
  26   /* Initial state, a new catcher has just been created.  */
  27   CATCHER_CREATED,
  28   /* The catch code is running.  */
  29   CATCHER_RUNNING,
  30   CATCHER_RUNNING_1,
  31   /* The catch code threw an exception.  */
  32   CATCHER_ABORTING
  33 };
  34
  35 /* Possible catcher actions.  */
  36 enum catcher_action {
  37   CATCH_ITER,
  38   CATCH_ITER_1,
  39   CATCH_THROWING
  40 };
  41
  42 struct catcher
  43 {
  44   enum catcher_state state = CATCHER_CREATED;
  45   /* Jump buffer pointing back at the exception handler.  */
  46   jmp_buf buf;
  47   /* Status buffer belonging to the exception handler.  */
  48   struct gdb_exception exception;
  49 };
  50
  51 /* Where to go for throw_exception().  */
  52 static std::forward_list<struct catcher> catchers;
  53
  54 jmp_buf *
  55 exceptions_state_mc_init ()
  56 {
  57   catchers.emplace_front ();
  58   return &catchers.front ().buf;
  59 }
  60
  61 /* Catcher state machine.  Returns non-zero if the m/c should be run
  62    again, zero if it should abort.  */
  63
  64 static int
  65 exceptions_state_mc (enum catcher_action action)
  66 {
  67   switch (catchers.front ().state)
  68     {
  69     case CATCHER_CREATED:
  70       switch (action)
  71         {
  72         case CATCH_ITER:
  73           /* Allow the code to run the catcher.  */
  74           catchers.front ().state = CATCHER_RUNNING;
  75           return 1;
  76         default:
  77           internal_error (__FILE__, __LINE__, _("bad state"));
  78         }
  79     case CATCHER_RUNNING:
  80       switch (action)
  81         {
  82         case CATCH_ITER:
  83           /* No error/quit has occured.  */
  84           return 0;
  85         case CATCH_ITER_1:
  86           catchers.front ().state = CATCHER_RUNNING_1;
  87           return 1;
  88         case CATCH_THROWING:
  89           catchers.front ().state = CATCHER_ABORTING;
  90           /* See also throw_exception.  */
  91           return 1;
  92         default:
  93           internal_error (__FILE__, __LINE__, _("bad switch"));
  94         }
  95     case CATCHER_RUNNING_1:
  96       switch (action)
  97         {
  98         case CATCH_ITER:
  99           /* The did a "break" from the inner while loop.  */
 100           return 0;
 101         case CATCH_ITER_1:
 102           catchers.front ().state = CATCHER_RUNNING;
 103           return 0;
 104         case CATCH_THROWING:
 105           catchers.front ().state = CATCHER_ABORTING;
 106           /* See also throw_exception.  */
 107           return 1;
 108         default:
 109           internal_error (__FILE__, __LINE__, _("bad switch"));
 110         }
 111     case CATCHER_ABORTING:
 112       switch (action)
 113         {
 114         case CATCH_ITER:
 115           {
 116             /* Exit normally if this catcher can handle this
 117                exception.  The caller analyses the func return
 118                values.  */
 119             return 0;
 120           }
 121         default:
 122           internal_error (__FILE__, __LINE__, _("bad state"));
 123         }
 124     default:
 125       internal_error (__FILE__, __LINE__, _("bad switch"));
 126     }
 127 }
 128
 129 int
 130 exceptions_state_mc_catch (struct gdb_exception *exception,
 131                            int mask)
 132 {
 133   *exception = std::move (catchers.front ().exception);
 134   catchers.pop_front ();
 135
 136   if (exception->reason < 0)
 137     {
 138       if (mask & RETURN_MASK (exception->reason))
 139         {
 140           /* Exit normally and let the caller handle the
 141              exception.  */
 142           return 1;
 143         }
 144
 145       /* The caller didn't request that the event be caught, relay the
 146          event to the next exception_catch/CATCH_SJLJ.  */
 147       throw_exception_sjlj (*exception);
 148     }
 149
 150   /* No exception was thrown.  */
 151   return 0;
 152 }
 153
 154 int
 155 exceptions_state_mc_action_iter (void)
 156 {
 157   return exceptions_state_mc (CATCH_ITER);
 158 }
 159
 160 int
 161 exceptions_state_mc_action_iter_1 (void)
 162 {
 163   return exceptions_state_mc (CATCH_ITER_1);
 164 }
 165
 166 /* Return EXCEPTION to the nearest containing CATCH_SJLJ block.  */
 167
 168 void
 169 throw_exception_sjlj (const struct gdb_exception &exception)
 170 {
 171   /* Jump to the nearest CATCH_SJLJ block, communicating REASON to
 172      that call via setjmp's return value.  Note that REASON can't be
 173      zero, by definition in common-exceptions.h.  */
 174   exceptions_state_mc (CATCH_THROWING);
 175   enum return_reason reason = exception.reason;
 176   catchers.front ().exception = exception;
 177   longjmp (catchers.front ().buf, reason);
 178 }
 179
 180 /* Implementation of throw_exception that uses C++ try/catch.  */
 181
 182 void
 183 throw_exception (gdb_exception &&exception)
 184 {
 185   if (exception.reason == RETURN_QUIT)
 186     throw gdb_exception_quit (std::move (exception));
 187   else if (exception.reason == RETURN_ERROR)
 188     throw gdb_exception_error (std::move (exception));
 189   else
 190     gdb_assert_not_reached ("invalid return reason");
 191 }
 192
 193 static void ATTRIBUTE_NORETURN ATTRIBUTE_PRINTF (3, 0)
 194 throw_it (enum return_reason reason, enum errors error, const char *fmt,
 195           va_list ap)
 196 {
 197   if (reason == RETURN_QUIT)
 198     throw gdb_exception_quit (fmt, ap);
 199   else if (reason == RETURN_ERROR)
 200     throw gdb_exception_error (error, fmt, ap);
 201   else
 202     gdb_assert_not_reached ("invalid return reason");
 203 }
 204
 205 void
 206 throw_verror (enum errors error, const char *fmt, va_list ap)
 207 {
 208   throw_it (RETURN_ERROR, error, fmt, ap);
 209 }
 210
 211 void
 212 throw_vquit (const char *fmt, va_list ap)
 213 {
 214   throw_it (RETURN_QUIT, GDB_NO_ERROR, fmt, ap);
 215 }
 216
 217 void
 218 throw_error (enum errors error, const char *fmt, ...)
 219 {
 220   va_list args;
 221
 222   va_start (args, fmt);
 223   throw_verror (error, fmt, args);
 224   va_end (args);
 225 }
 226
 227 void
 228 throw_quit (const char *fmt, ...)
 229 {
 230   va_list args;
 231
 232   va_start (args, fmt);
 233   throw_vquit (fmt, args);
 234   va_end (args);
 235 }