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

   1 // -*- C++ -*- Allocate exception objects.
   2 // Copyright (C) 2001-2014 Free Software Foundation, Inc.
   3 //
   4 // This file is part of GCC.
   5 //
   6 // GCC 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 3, or (at your option)
   9 // any later version.
  10 //
  11 // GCC 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 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 // This is derived from the C++ ABI for IA-64.  Where we diverge
  26 // for cross-architecture compatibility are noted with "@@@".
  27
  28 #include <bits/c++config.h>
  29 #include <cstdlib>
  30 #if _GLIBCXX_HOSTED
  31 #include <cstring>
  32 #endif
  33 #include <climits>
  34 #include <exception>
  35 #include "unwind-cxx.h"
  36 #include <ext/concurrence.h>
  37
  38 #if _GLIBCXX_HOSTED
  39 using std::free;
  40 using std::malloc;
  41 using std::memset;
  42 #else
  43 // In a freestanding environment, these functions may not be available
  44 // -- but for now, we assume that they are.
  45 extern "C" void *malloc (std::size_t);
  46 extern "C" void free(void *);
  47 extern "C" void *memset (void *, int, std::size_t);
  48 #endif
  49
  50 using namespace __cxxabiv1;
  51
  52 // ??? How to control these parameters.
  53
  54 // Guess from the size of basic types how large a buffer is reasonable.
  55 // Note that the basic c++ exception header has 13 pointers and 2 ints,
  56 // so on a system with PSImode pointers we're talking about 56 bytes
  57 // just for overhead.
  58
  59 #if INT_MAX == 32767
  60 # define EMERGENCY_OBJ_SIZE     128
  61 # define EMERGENCY_OBJ_COUNT    16
  62 #elif !defined (_GLIBCXX_LLP64) && LONG_MAX == 2147483647
  63 # define EMERGENCY_OBJ_SIZE     512
  64 # define EMERGENCY_OBJ_COUNT    32
  65 #else
  66 # define EMERGENCY_OBJ_SIZE     1024
  67 # define EMERGENCY_OBJ_COUNT    64
  68 #endif
  69
  70 #ifndef __GTHREADS
  71 # undef EMERGENCY_OBJ_COUNT
  72 # define EMERGENCY_OBJ_COUNT    4
  73 #endif
  74
  75 #if INT_MAX == 32767 || EMERGENCY_OBJ_COUNT <= 32
  76 typedef unsigned int bitmask_type;
  77 #else
  78 #if defined (_GLIBCXX_LLP64)
  79 typedef unsigned long long bitmask_type;
  80 #else
  81 typedef unsigned long bitmask_type;
  82 #endif
  83 #endif
  84
  85
  86 typedef char one_buffer[EMERGENCY_OBJ_SIZE] __attribute__((aligned));
  87 static one_buffer emergency_buffer[EMERGENCY_OBJ_COUNT];
  88 static bitmask_type emergency_used;
  89
  90 static __cxa_dependent_exception dependents_buffer[EMERGENCY_OBJ_COUNT];
  91 static bitmask_type dependents_used;
  92
  93 namespace
  94 {
  95   // A single mutex controlling emergency allocations.
  96   __gnu_cxx::__mutex emergency_mutex;
  97 }
  98
  99 extern "C" void *
 100 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
 101 {
 102   void *ret;
 103
 104   thrown_size += sizeof (__cxa_refcounted_exception);
 105   ret = malloc (thrown_size);
 106
 107   if (! ret)
 108     {
 109       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 110
 111       bitmask_type used = emergency_used;
 112       unsigned int which = 0;
 113
 114       if (thrown_size > EMERGENCY_OBJ_SIZE)
 115         goto failed;
 116       while (used & 1)
 117         {
 118           used >>= 1;
 119           if (++which >= EMERGENCY_OBJ_COUNT)
 120             goto failed;
 121         }
 122
 123       emergency_used |= (bitmask_type)1 << which;
 124       ret = &emergency_buffer[which][0];
 125
 126     failed:;
 127
 128       if (!ret)
 129         std::terminate ();
 130     }
 131
 132   memset (ret, 0, sizeof (__cxa_refcounted_exception));
 133
 134   return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
 135 }
 136
 137
 138 extern "C" void
 139 __cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
 140 {
 141   char *base = (char *) emergency_buffer;
 142   char *ptr = (char *) vptr;
 143   if (ptr >= base
 144       && ptr < base + sizeof (emergency_buffer))
 145     {
 146       const unsigned int which
 147         = (unsigned) (ptr - base) / EMERGENCY_OBJ_SIZE;
 148
 149       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 150       emergency_used &= ~((bitmask_type)1 << which);
 151     }
 152   else
 153     free (ptr - sizeof (__cxa_refcounted_exception));
 154 }
 155
 156
 157 extern "C" __cxa_dependent_exception*
 158 __cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
 159 {
 160   __cxa_dependent_exception *ret;
 161
 162   ret = static_cast<__cxa_dependent_exception*>
 163     (malloc (sizeof (__cxa_dependent_exception)));
 164
 165   if (!ret)
 166     {
 167       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 168
 169       bitmask_type used = dependents_used;
 170       unsigned int which = 0;
 171
 172       while (used & 1)
 173         {
 174           used >>= 1;
 175           if (++which >= EMERGENCY_OBJ_COUNT)
 176             goto failed;
 177         }
 178
 179       dependents_used |= (bitmask_type)1 << which;
 180       ret = &dependents_buffer[which];
 181
 182     failed:;
 183
 184       if (!ret)
 185         std::terminate ();
 186     }
 187
 188   memset (ret, 0, sizeof (__cxa_dependent_exception));
 189
 190   return ret;
 191 }
 192
 193
 194 extern "C" void
 195 __cxxabiv1::__cxa_free_dependent_exception
 196   (__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
 197 {
 198   char *base = (char *) dependents_buffer;
 199   char *ptr = (char *) vptr;
 200   if (ptr >= base
 201       && ptr < base + sizeof (dependents_buffer))
 202     {
 203       const unsigned int which
 204         = (unsigned) (ptr - base) / sizeof (__cxa_dependent_exception);
 205
 206       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 207       dependents_used &= ~((bitmask_type)1 << which);
 208     }
 209   else
 210     free (vptr);
 211 }