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 !defined (_GLIBCXX_LLP64) && 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 #if defined (_GLIBCXX_LLP64)
  80 typedef unsigned long long bitmask_type;
  81 #else
  82 typedef unsigned long bitmask_type;
  83 #endif
  84 #endif
  85
  86
  87 typedef char one_buffer[EMERGENCY_OBJ_SIZE] __attribute__((aligned));
  88 static one_buffer emergency_buffer[EMERGENCY_OBJ_COUNT];
  89 static bitmask_type emergency_used;
  90
  91 static __cxa_dependent_exception dependents_buffer[EMERGENCY_OBJ_COUNT];
  92 static bitmask_type dependents_used;
  93
  94 namespace
  95 {
  96   // A single mutex controlling emergency allocations.
  97   __gnu_cxx::__mutex emergency_mutex;
  98 }
  99
 100 extern "C" void *
 101 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
 102 {
 103   void *ret;
 104
 105   thrown_size += sizeof (__cxa_refcounted_exception);
 106   ret = malloc (thrown_size);
 107
 108   if (! ret)
 109     {
 110       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 111
 112       bitmask_type used = emergency_used;
 113       unsigned int which = 0;
 114
 115       if (thrown_size > EMERGENCY_OBJ_SIZE)
 116         goto failed;
 117       while (used & 1)
 118         {
 119           used >>= 1;
 120           if (++which >= EMERGENCY_OBJ_COUNT)
 121             goto failed;
 122         }
 123
 124       emergency_used |= (bitmask_type)1 << which;
 125       ret = &emergency_buffer[which][0];
 126
 127     failed:;
 128
 129       if (!ret)
 130         std::terminate ();
 131     }
 132
 133   // We have an uncaught exception as soon as we allocate memory.  This
 134   // yields uncaught_exception() true during the copy-constructor that
 135   // initializes the exception object.  See Issue 475.
 136   __cxa_eh_globals *globals = __cxa_get_globals ();
 137   globals->uncaughtExceptions += 1;
 138
 139   memset (ret, 0, sizeof (__cxa_refcounted_exception));
 140
 141   return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
 142 }
 143
 144
 145 extern "C" void
 146 __cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
 147 {
 148   char *base = (char *) emergency_buffer;
 149   char *ptr = (char *) vptr;
 150   if (ptr >= base
 151       && ptr < base + sizeof (emergency_buffer))
 152     {
 153       const unsigned int which
 154         = (unsigned) (ptr - base) / EMERGENCY_OBJ_SIZE;
 155
 156       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 157       emergency_used &= ~((bitmask_type)1 << which);
 158     }
 159   else
 160     free (ptr - sizeof (__cxa_refcounted_exception));
 161 }
 162
 163
 164 extern "C" __cxa_dependent_exception*
 165 __cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
 166 {
 167   __cxa_dependent_exception *ret;
 168
 169   ret = static_cast<__cxa_dependent_exception*>
 170     (malloc (sizeof (__cxa_dependent_exception)));
 171
 172   if (!ret)
 173     {
 174       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 175
 176       bitmask_type used = dependents_used;
 177       unsigned int which = 0;
 178
 179       while (used & 1)
 180         {
 181           used >>= 1;
 182           if (++which >= EMERGENCY_OBJ_COUNT)
 183             goto failed;
 184         }
 185
 186       dependents_used |= (bitmask_type)1 << which;
 187       ret = &dependents_buffer[which];
 188
 189     failed:;
 190
 191       if (!ret)
 192         std::terminate ();
 193     }
 194
 195   // We have an uncaught exception as soon as we allocate memory.  This
 196   // yields uncaught_exception() true during the copy-constructor that
 197   // initializes the exception object.  See Issue 475.
 198   __cxa_eh_globals *globals = __cxa_get_globals ();
 199   globals->uncaughtExceptions += 1;
 200
 201   memset (ret, 0, sizeof (__cxa_dependent_exception));
 202
 203   return ret;
 204 }
 205
 206
 207 extern "C" void
 208 __cxxabiv1::__cxa_free_dependent_exception
 209   (__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
 210 {
 211   char *base = (char *) dependents_buffer;
 212   char *ptr = (char *) vptr;
 213   if (ptr >= base
 214       && ptr < base + sizeof (dependents_buffer))
 215     {
 216       const unsigned int which
 217         = (unsigned) (ptr - base) / sizeof (__cxa_dependent_exception);
 218
 219       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 220       dependents_used &= ~((bitmask_type)1 << which);
 221     }
 222   else
 223     free (vptr);
 224 }