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

   1 // -*- C++ -*- Allocate exception objects.
   2 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006
   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 namespace
  93 {
  94   // A single mutex controlling emergency allocations.
  95   __gnu_cxx::__mutex emergency_mutex;
  96 }
  97
  98 extern "C" void *
  99 __cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) throw()
 100 {
 101   void *ret;
 102
 103   thrown_size += sizeof (__cxa_exception);
 104   ret = malloc (thrown_size);
 105
 106   if (! ret)
 107     {
 108       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 109
 110       bitmask_type used = emergency_used;
 111       unsigned int which = 0;
 112
 113       if (thrown_size > EMERGENCY_OBJ_SIZE)
 114         goto failed;
 115       while (used & 1)
 116         {
 117           used >>= 1;
 118           if (++which >= EMERGENCY_OBJ_COUNT)
 119             goto failed;
 120         }
 121
 122       emergency_used |= (bitmask_type)1 << which;
 123       ret = &emergency_buffer[which][0];
 124
 125     failed:;
 126
 127       if (!ret)
 128         std::terminate ();
 129     }
 130
 131   // We have an uncaught exception as soon as we allocate memory.  This
 132   // yields uncaught_exception() true during the copy-constructor that
 133   // initializes the exception object.  See Issue 475.
 134   __cxa_eh_globals *globals = __cxa_get_globals ();
 135   globals->uncaughtExceptions += 1;
 136
 137   memset (ret, 0, sizeof (__cxa_exception));
 138
 139   return (void *)((char *)ret + sizeof (__cxa_exception));
 140 }
 141
 142
 143 extern "C" void
 144 __cxxabiv1::__cxa_free_exception(void *vptr) throw()
 145 {
 146   char *ptr = (char *) vptr;
 147   if (ptr >= &emergency_buffer[0][0]
 148       && ptr < &emergency_buffer[0][0] + sizeof (emergency_buffer))
 149     {
 150       const unsigned int which
 151         = (unsigned)(ptr - &emergency_buffer[0][0]) / EMERGENCY_OBJ_SIZE;
 152
 153       __gnu_cxx::__scoped_lock sentry(emergency_mutex);
 154       emergency_used &= ~((bitmask_type)1 << which);
 155     }
 156   else
 157     free (ptr - sizeof (__cxa_exception));
 158 }