libstdc++-v3/libsupc++/eh_alloc.cc

   1 // -*- C++ -*- Allocate exception objects.
   2 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008
   3 // Free Software Foundation, Inc.
   4 //
   5 // This file is part of GCC.
   6 //
   7 // GCC 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 2, or (at your option)
  10 // any later version.
  11 //
  12 // GCC 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 GCC; see the file COPYING.  If not, write to
  19 // the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  20 // Boston, MA 02110-1301, USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 // This is derived from the C++ ABI for IA-64.  Where we diverge
  32 // for cross-architecture compatibility are noted with "@@@".
  33
  34 #include <bits/c++config.h>
  35 #include <cstdlib>
  36 #if _GLIBCXX_HOSTED
  37 #include <cstring>
  38 #endif
  39 #include <climits>
  40 #include <exception>
  41 #include "unwind-cxx.h"
  42 #include <ext/concurrence.h>
  43
  44 #if _GLIBCXX_HOSTED
  45 using std::free;
  46 using std::malloc;
  47 using std::memset;
  48 #else
  49 // In a freestanding environment, these functions may not be available
  50 // -- but for now, we assume that they are.
  51 extern "C" void *malloc (std::size_t);
  52 extern "C" void free(void *);
  53 extern "C" void *memset (void *, int, std::size_t);
  54 #endif
  55
  56 using namespace __cxxabiv1;
  57
  58 // ??? How to control these parameters.
  59
  60 // Guess from the size of basic types how large a buffer is reasonable.
  61 // Note that the basic c++ exception header has 13 pointers and 2 ints,
  62 // so on a system with PSImode pointers we're talking about 56 bytes
  63 // just for overhead.
  64
  65 #if INT_MAX == 32767
  66 # define EMERGENCY_OBJ_SIZE     128
  67 # define EMERGENCY_OBJ_COUNT    16
  68 #elif LONG_MAX == 2147483647
  69 # define EMERGENCY_OBJ_SIZE     512
  70 # define EMERGENCY_OBJ_COUNT    32
  71 #else
  72 # define EMERGENCY_OBJ_SIZE     1024
  73 # define EMERGENCY_OBJ_COUNT    64
  74 #endif
  75
  76 #ifndef __GTHREADS
  77 # undef EMERGENCY_OBJ_COUNT
  78 # define EMERGENCY_OBJ_COUNT    4
  79 #endif
  80
  81 #if INT_MAX == 32767 || EMERGENCY_OBJ_COUNT <= 32
  82 typedef unsigned int bitmask_type;
  83 #else
  84 typedef unsigned long bitmask_type;
  85 #endif
  86
  87
  88 typedef char one_buffer[EMERGENCY_OBJ_SIZE] __attribute__((aligned));
  89 static one_buffer emergency_buffer[EMERGENCY_OBJ_COUNT];
  90 static bitmask_type emergency_used;
  91
  92 static __cxa_dependent_exception dependents_buffer[EMERGENCY_OBJ_COUNT];
  93 static bitmask_type dependents_used;
  94
  95 namespace
  96 {
  97   // A single mutex controlling emergency allocations.
  98   __gnu_cxx::__mutex emergency_mutex;
  99 }
 100
 101 extern "C" void *
 102 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) throw()
 103 {
 104   void *ret;
 105
 106   thrown_size += sizeof (__cxa_exception);
 107   ret = malloc (thrown_size);
 108
 109   if (! ret)
 110     {
 111       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 112
 113       bitmask_type used = emergency_used;
 114       unsigned int which = 0;
 115
 116       if (thrown_size > EMERGENCY_OBJ_SIZE)
 117         goto failed;
 118       while (used & 1)
 119         {
 120           used >>= 1;
 121           if (++which >= EMERGENCY_OBJ_COUNT)
 122             goto failed;
 123         }
 124
 125       emergency_used |= (bitmask_type)1 << which;
 126       ret = &emergency_buffer[which][0];
 127
 128     failed:;
 129
 130       if (!ret)
 131         std::terminate ();
 132     }
 133
 134   // We have an uncaught exception as soon as we allocate memory.  This
 135   // yields uncaught_exception() true during the copy-constructor that
 136   // initializes the exception object.  See Issue 475.
 137   __cxa_eh_globals *globals = __cxa_get_globals ();
 138   globals->uncaughtExceptions += 1;
 139
 140   memset (ret, 0, sizeof (__cxa_exception));
 141
 142   return (void *)((char *)ret + sizeof (__cxa_exception));
 143 }
 144
 145
 146 extern "C" void
 147 __cxxabiv1::__cxa_free_exception(void *vptr) throw()
 148 {
 149   char *base = (char *) emergency_buffer;
 150   char *ptr = (char *) vptr;
 151   if (ptr >= base
 152       && ptr < base + sizeof (emergency_buffer))
 153     {
 154       const unsigned int which
 155         = (unsigned) (ptr - base) / EMERGENCY_OBJ_SIZE;
 156
 157       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 158       emergency_used &= ~((bitmask_type)1 << which);
 159     }
 160   else
 161     free (ptr - sizeof (__cxa_exception));
 162 }
 163
 164
 165 extern "C" __cxa_dependent_exception*
 166 __cxxabiv1::__cxa_allocate_dependent_exception() throw()
 167 {
 168   __cxa_dependent_exception *ret;
 169
 170   ret = static_cast<__cxa_dependent_exception*>
 171     (malloc (sizeof (__cxa_dependent_exception)));
 172
 173   if (!ret)
 174     {
 175       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 176
 177       bitmask_type used = dependents_used;
 178       unsigned int which = 0;
 179
 180       while (used & 1)
 181         {
 182           used >>= 1;
 183           if (++which >= EMERGENCY_OBJ_COUNT)
 184             goto failed;
 185         }
 186
 187       dependents_used |= (bitmask_type)1 << which;
 188       ret = &dependents_buffer[which];
 189
 190     failed:;
 191
 192       if (!ret)
 193         std::terminate ();
 194     }
 195
 196   // We have an uncaught exception as soon as we allocate memory.  This
 197   // yields uncaught_exception() true during the copy-constructor that
 198   // initializes the exception object.  See Issue 475.
 199   __cxa_eh_globals *globals = __cxa_get_globals ();
 200   globals->uncaughtExceptions += 1;
 201
 202   memset (ret, 0, sizeof (__cxa_dependent_exception));
 203
 204   return ret;
 205 }
 206
 207
 208 extern "C" void
 209 __cxxabiv1::__cxa_free_dependent_exception
 210   (__cxa_dependent_exception *vptr) throw()
 211 {
 212   char *base = (char *) dependents_buffer;
 213   char *ptr = (char *) vptr;
 214   if (ptr >= base
 215       && ptr < base + sizeof (dependents_buffer))
 216     {
 217       const unsigned int which
 218         = (unsigned) (ptr - base) / sizeof (__cxa_dependent_exception);
 219
 220       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 221       dependents_used &= ~((bitmask_type)1 << which);
 222     }
 223   else
 224     free (vptr);
 225 }