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

   1 // -*- C++ -*- Allocate exception objects.
   2 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009, 2011
   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 3, 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 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 // This is derived from the C++ ABI for IA-64.  Where we diverge
  27 // for cross-architecture compatibility are noted with "@@@".
  28
  29 #include <bits/c++config.h>
  30 #include <cstdlib>
  31 #if _GLIBCXX_HOSTED
  32 #include <cstring>
  33 #endif
  34 #include <climits>
  35 #include <exception>
  36 #include "unwind-cxx.h"
  37 #include <ext/concurrence.h>
  38
  39 #if _GLIBCXX_HOSTED
  40 using std::free;
  41 using std::malloc;
  42 using std::memset;
  43 #else
  44 // In a freestanding environment, these functions may not be available
  45 // -- but for now, we assume that they are.
  46 extern "C" void *malloc (std::size_t);
  47 extern "C" void free(void *);
  48 extern "C" void *memset (void *, int, std::size_t);
  49 #endif
  50
  51 using namespace __cxxabiv1;
  52
  53 // ??? How to control these parameters.
  54
  55 // Guess from the size of basic types how large a buffer is reasonable.
  56 // Note that the basic c++ exception header has 13 pointers and 2 ints,
  57 // so on a system with PSImode pointers we're talking about 56 bytes
  58 // just for overhead.
  59
  60 #if INT_MAX == 32767
  61 # define EMERGENCY_OBJ_SIZE     128
  62 # define EMERGENCY_OBJ_COUNT    16
  63 #elif LONG_MAX == 2147483647
  64 # define EMERGENCY_OBJ_SIZE     512
  65 # define EMERGENCY_OBJ_COUNT    32
  66 #else
  67 # define EMERGENCY_OBJ_SIZE     1024
  68 # define EMERGENCY_OBJ_COUNT    64
  69 #endif
  70
  71 #ifndef __GTHREADS
  72 # undef EMERGENCY_OBJ_COUNT
  73 # define EMERGENCY_OBJ_COUNT    4
  74 #endif
  75
  76 #if INT_MAX == 32767 || EMERGENCY_OBJ_COUNT <= 32
  77 typedef unsigned int bitmask_type;
  78 #else
  79 typedef unsigned long bitmask_type;
  80 #endif
  81
  82
  83 typedef char one_buffer[EMERGENCY_OBJ_SIZE] __attribute__((aligned));
  84 static one_buffer emergency_buffer[EMERGENCY_OBJ_COUNT];
  85 static bitmask_type emergency_used;
  86
  87 static __cxa_dependent_exception dependents_buffer[EMERGENCY_OBJ_COUNT];
  88 static bitmask_type dependents_used;
  89
  90 namespace
  91 {
  92   // A single mutex controlling emergency allocations.
  93   __gnu_cxx::__mutex emergency_mutex;
  94 }
  95
  96 extern "C" void *
  97 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
  98 {
  99   void *ret;
 100
 101   thrown_size += sizeof (__cxa_refcounted_exception);
 102   ret = malloc (thrown_size);
 103
 104   if (! ret)
 105     {
 106       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 107
 108       bitmask_type used = emergency_used;
 109       unsigned int which = 0;
 110
 111       if (thrown_size > EMERGENCY_OBJ_SIZE)
 112         goto failed;
 113       while (used & 1)
 114         {
 115           used >>= 1;
 116           if (++which >= EMERGENCY_OBJ_COUNT)
 117             goto failed;
 118         }
 119
 120       emergency_used |= (bitmask_type)1 << which;
 121       ret = &emergency_buffer[which][0];
 122
 123     failed:;
 124
 125       if (!ret)
 126         std::terminate ();
 127     }
 128
 129   // We have an uncaught exception as soon as we allocate memory.  This
 130   // yields uncaught_exception() true during the copy-constructor that
 131   // initializes the exception object.  See Issue 475.
 132   __cxa_eh_globals *globals = __cxa_get_globals ();
 133   globals->uncaughtExceptions += 1;
 134
 135   memset (ret, 0, sizeof (__cxa_refcounted_exception));
 136
 137   return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
 138 }
 139
 140
 141 extern "C" void
 142 __cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
 143 {
 144   char *base = (char *) emergency_buffer;
 145   char *ptr = (char *) vptr;
 146   if (ptr >= base
 147       && ptr < base + sizeof (emergency_buffer))
 148     {
 149       const unsigned int which
 150         = (unsigned) (ptr - base) / EMERGENCY_OBJ_SIZE;
 151
 152       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 153       emergency_used &= ~((bitmask_type)1 << which);
 154     }
 155   else
 156     free (ptr - sizeof (__cxa_refcounted_exception));
 157 }
 158
 159
 160 extern "C" __cxa_dependent_exception*
 161 __cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
 162 {
 163   __cxa_dependent_exception *ret;
 164
 165   ret = static_cast<__cxa_dependent_exception*>
 166     (malloc (sizeof (__cxa_dependent_exception)));
 167
 168   if (!ret)
 169     {
 170       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 171
 172       bitmask_type used = dependents_used;
 173       unsigned int which = 0;
 174
 175       while (used & 1)
 176         {
 177           used >>= 1;
 178           if (++which >= EMERGENCY_OBJ_COUNT)
 179             goto failed;
 180         }
 181
 182       dependents_used |= (bitmask_type)1 << which;
 183       ret = &dependents_buffer[which];
 184
 185     failed:;
 186
 187       if (!ret)
 188         std::terminate ();
 189     }
 190
 191   // We have an uncaught exception as soon as we allocate memory.  This
 192   // yields uncaught_exception() true during the copy-constructor that
 193   // initializes the exception object.  See Issue 475.
 194   __cxa_eh_globals *globals = __cxa_get_globals ();
 195   globals->uncaughtExceptions += 1;
 196
 197   memset (ret, 0, sizeof (__cxa_dependent_exception));
 198
 199   return ret;
 200 }
 201
 202
 203 extern "C" void
 204 __cxxabiv1::__cxa_free_dependent_exception
 205   (__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
 206 {
 207   char *base = (char *) dependents_buffer;
 208   char *ptr = (char *) vptr;
 209   if (ptr >= base
 210       && ptr < base + sizeof (dependents_buffer))
 211     {
 212       const unsigned int which
 213         = (unsigned) (ptr - base) / sizeof (__cxa_dependent_exception);
 214
 215       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 216       dependents_used &= ~((bitmask_type)1 << which);
 217     }
 218   else
 219     free (vptr);
 220 }