gcc/cp/exception.cc

   1 // Functions for Exception Support for -*- C++ -*-
   2 // Copyright (C) 1994, 1995, 1996 Free Software Foundation
   3
   4 // This file is part of GNU CC.
   5
   6 // GNU CC is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 2, or (at your option)
   9 // any later version.
  10
  11 // GNU CC is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // You should have received a copy of the GNU General Public License
  17 // along with GNU CC; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330,
  19 // Boston, MA 02111-1307, USA.
  20
  21 // As a special exception, if you link this library with other files,
  22 // some of which are compiled with GCC, to produce an executable,
  23 // this library does not by itself cause the resulting executable
  24 // to be covered by the GNU General Public License.
  25 // This exception does not however invalidate any other reasons why
  26 // the executable file might be covered by the GNU General Public License.
  27
  28 #pragma implementation "exception"
  29
  30 #include "typeinfo"
  31 #include "exception"
  32 #include <stddef.h>
  33
  34 /* Define terminate, unexpected, set_terminate, set_unexpected as
  35    well as the default terminate func and default unexpected func.  */
  36
  37 extern terminate_handler __terminate_func __attribute__((__noreturn__));
  38
  39 void
  40 terminate ()
  41 {
  42   __terminate_func ();
  43 }
  44
  45 void
  46 __default_unexpected ()
  47 {
  48   terminate ();
  49 }
  50
  51 static unexpected_handler __unexpected_func __attribute__((__noreturn__))
  52   = __default_unexpected;
  53
  54 terminate_handler
  55 set_terminate (terminate_handler func)
  56 {
  57   terminate_handler old = __terminate_func;
  58
  59   __terminate_func = func;
  60   return old;
  61 }
  62
  63 unexpected_handler
  64 set_unexpected (unexpected_handler func)
  65 {
  66   unexpected_handler old = __unexpected_func;
  67
  68   __unexpected_func = func;
  69   return old;
  70 }
  71
  72 void
  73 unexpected ()
  74 {
  75   __unexpected_func ();
  76 }
  77
  78 /* C++-specific state about the current exception.
  79    This must match init_exception_processing().
  80
  81    Note that handlers and caught are not redundant; when rethrown, an
  82    exception can have multiple active handlers and still be considered
  83    uncaught.  */
  84
  85 struct cp_eh_info
  86 {
  87   void *value;
  88   void *type;
  89   void (*cleanup)(void *, int);
  90   bool caught;
  91   cp_eh_info *next;
  92   long handlers;
  93 };
  94
  95 /* Language-specific EH info pointer, defined in libgcc2. */
  96
  97 extern "C" cp_eh_info **__get_eh_info ();       // actually void **
  98
  99 /* Is P the type_info node for a pointer of some kind?  */
 100
 101 extern bool __is_pointer (void *);
 102
 103 /* Compiler hook to return a pointer to the info for the current exception.
 104    Used by get_eh_info ().  */
 105
 106 extern "C" cp_eh_info *
 107 __cp_exception_info (void)
 108 {
 109   return *__get_eh_info ();
 110 }
 111
 112 /* Allocate a buffer for a cp_eh_info and an exception object of size SIZE,
 113    and return a pointer to the beginning of the object's space.  */
 114
 115 extern "C" void * malloc (size_t);
 116 extern "C" void *
 117 __eh_alloc (size_t size)
 118 {
 119   void *p = malloc (size);
 120   if (p == 0)
 121     terminate ();
 122   return p;
 123 }
 124
 125 /* Free the memory for an cp_eh_info and associated exception, given
 126    a pointer to the cp_eh_info.  */
 127
 128 extern "C" void free (void *);
 129 extern "C" void
 130 __eh_free (void *p)
 131 {
 132   free (p);
 133 }
 134
 135 /* Compiler hook to push a new exception onto the stack.
 136    Used by expand_throw().  */
 137
 138 extern "C" void
 139 __cp_push_exception (void *value, void *type, void (*cleanup)(void *, int))
 140 {
 141   cp_eh_info *p = (cp_eh_info *) __eh_alloc (sizeof (cp_eh_info));
 142
 143   p->value = value;
 144   p->type = type;
 145   p->cleanup = cleanup;
 146   p->handlers = 0;
 147   p->caught = false;
 148
 149   cp_eh_info **q = __get_eh_info ();
 150
 151   p->next = *q;
 152   *q = p;
 153 }
 154
 155 /* Compiler hook to pop an exception that has been finalized.  Used by
 156    push_eh_cleanup().  P is the info for the exception caught by the
 157    current catch block.  */
 158
 159 extern "C" void
 160 __cp_pop_exception (cp_eh_info *p)
 161 {
 162   cp_eh_info **q = __get_eh_info ();
 163
 164   --p->handlers;
 165
 166   /* Don't really pop if there are still active handlers for our exception,
 167      or if our exception is being rethrown (i.e. if the active exception is
 168      our exception and it is uncaught).  */
 169   if (p->handlers != 0
 170       || (p == *q && !p->caught))
 171     return;
 172
 173   for (; *q; q = &((*q)->next))
 174     if (*q == p)
 175       break;
 176
 177   if (! *q)
 178     terminate ();
 179
 180   *q = p->next;
 181
 182   if (p->cleanup)
 183     /* 2 is a magic value for destructors; see build_delete().  */
 184     p->cleanup (p->value, 2);
 185
 186   if (! __is_pointer (p->type))
 187     __eh_free (p->value);
 188
 189   __eh_free (p);
 190 }
 191
 192 extern "C" void
 193 __uncatch_exception (void)
 194 {
 195   cp_eh_info *p = __cp_exception_info ();
 196   if (p == 0)
 197     terminate ();
 198   p->caught = false;
 199 }
 200
 201 /* As per [except.unexpected]:
 202    If an exception is thrown, we check it against the spec.  If it doesn't
 203    match, we call unexpected ().  If unexpected () throws, we check that
 204    exception against the spec.  If it doesn't match, if the spec allows
 205    bad_exception we throw that; otherwise we call terminate ().
 206
 207    The compiler treats an exception spec as a try block with a generic
 208    handler that just calls this function with a list of the allowed
 209    exception types, so we have an active exception that can be rethrown.
 210
 211    This function does not return.  */
 212
 213 extern "C" void
 214 __check_eh_spec (int n, const void **spec)
 215 {
 216   cp_eh_info *p = __cp_exception_info ();
 217
 218   for (int i = 0; i < n; ++i)
 219     {
 220       if (__throw_type_match_rtti (spec[i], p->type, p->value))
 221         throw;
 222     }
 223
 224   try
 225     {
 226       unexpected ();
 227     }
 228   catch (...)
 229     {
 230       // __exception_info is an artificial var pushed into each catch block.
 231       if (p != __exception_info)
 232         {
 233           p = __exception_info;
 234           for (int i = 0; i < n; ++i)
 235             {
 236               if (__throw_type_match_rtti (spec[i], p->type, p->value))
 237                 throw;
 238             }
 239         }
 240
 241       const type_info &bad_exc = typeid (bad_exception);
 242       for (int i = 0; i < n; ++i)
 243         {
 244           if (__throw_type_match_rtti (spec[i], &bad_exc, p->value))
 245             throw bad_exception ();
 246         }
 247
 248       terminate ();
 249     }
 250 }
 251
 252 extern "C" void
 253 __throw_bad_cast (void)
 254 {
 255   throw bad_cast ();
 256 }
 257
 258 extern "C" void
 259 __throw_bad_typeid (void)
 260 {
 261   throw bad_typeid ();
 262 }
 263
 264 /* Has the current exception been caught?  */
 265
 266 bool
 267 uncaught_exception ()
 268 {
 269   cp_eh_info *p = __cp_exception_info ();
 270   return p && ! p->caught;
 271 }
 272
 273 const char * exception::
 274 what () const
 275 {
 276   return typeid (*this).name ();
 277 }