// -*- C++ -*- Allocate exception objects.
// Copyright (C) 2001-2015 Free Software Foundation, Inc.
//
// This file is part of GCC.
//
// GCC is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3, or (at your option)
// any later version.
//
// GCC is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
// This is derived from the C++ ABI for IA-64. Where we diverge
// for cross-architecture compatibility are noted with "@@@".
#include <bits/c++config.h>
#include <cstdlib>
#if _GLIBCXX_HOSTED
#include <cstring>
#endif
#include <climits>
#include <exception>
#include "unwind-cxx.h"
#include <ext/concurrence.h>
#include <new>
#if _GLIBCXX_HOSTED
using std::free;
using std::malloc;
using std::memset;
#else
// In a freestanding environment, these functions may not be available
// -- but for now, we assume that they are.
extern "C" void *malloc (std::size_t);
extern "C" void free(void *);
extern "C" void *memset (void *, int, std::size_t);
#endif
using namespace __cxxabiv1;
// ??? How to control these parameters.
// Guess from the size of basic types how large a buffer is reasonable.
// Note that the basic c++ exception header has 13 pointers and 2 ints,
// so on a system with PSImode pointers we're talking about 56 bytes
// just for overhead.
#if INT_MAX == 32767
# define EMERGENCY_OBJ_SIZE 128
# define EMERGENCY_OBJ_COUNT 16
#elif !defined (_GLIBCXX_LLP64) && LONG_MAX == 2147483647
# define EMERGENCY_OBJ_SIZE 512
# define EMERGENCY_OBJ_COUNT 32
#else
# define EMERGENCY_OBJ_SIZE 1024
# define EMERGENCY_OBJ_COUNT 64
#endif
#ifndef __GTHREADS
# undef EMERGENCY_OBJ_COUNT
# define EMERGENCY_OBJ_COUNT 4
#endif
namespace
{
// A fixed-size heap, variable size object allocator
class pool
{
public:
pool();
void *allocate (std::size_t);
void free (void *);
bool in_pool (void *);
private:
struct free_entry {
std::size_t size;
free_entry *next;
};
struct allocated_entry {
std::size_t size;
char data[] __attribute__((aligned));
};
// A single mutex controlling emergency allocations.
__gnu_cxx::__mutex emergency_mutex;
// The free-list
free_entry *first_free_entry;
// The arena itself - we need to keep track of these only
// to implement in_pool.
char *arena;
std::size_t arena_size;
};
pool::pool()
{
// Allocate the arena - we could add a GLIBCXX_EH_ARENA_SIZE environment
// to make this tunable.
arena_size = (EMERGENCY_OBJ_SIZE * EMERGENCY_OBJ_COUNT
+ EMERGENCY_OBJ_COUNT * sizeof (__cxa_dependent_exception));
arena = (char *)malloc (arena_size);
if (!arena)
{
// If the allocation failed go without an emergency pool.
arena_size = 0;
first_free_entry = NULL;
return;
}
// Populate the free-list with a single entry covering the whole arena
first_free_entry = reinterpret_cast <free_entry *> (arena);
new (first_free_entry) free_entry;
first_free_entry->size = arena_size;
first_free_entry->next = NULL;
}
void *pool::allocate (std::size_t size)
{
__gnu_cxx::__scoped_lock sentry(emergency_mutex);
// We need an additional size_t member plus the padding to
// ensure proper alignment of data.
size += offsetof (allocated_entry, data);
// And we need to at least hand out objects of the size of
// a freelist entry.
if (size < sizeof (free_entry))
size = sizeof (free_entry);
// And we need to align objects we hand out to the maximum
// alignment required on the target (this really aligns the
// tail which will become a new freelist entry).
size = ((size + __alignof__ (allocated_entry::data) - 1)
& ~(__alignof__ (allocated_entry::data) - 1));
// Search for an entry of proper size on the freelist.
free_entry **e;
for (e = &first_free_entry;
*e && (*e)->size < size;
e = &(*e)->next)
;
if (!*e)
return NULL;
allocated_entry *x;
if ((*e)->size - size >= sizeof (free_entry))
{
// Slit block if it is too large.
free_entry *f = reinterpret_cast <free_entry *>
(reinterpret_cast <char *> (*e) + size);
std::size_t sz = (*e)->size;
free_entry *next = (*e)->next;
new (f) free_entry;
f->next = next;
f->size = sz - size;
x = reinterpret_cast <allocated_entry *> (*e);
new (x) allocated_entry;
x->size = size;
*e = f;
}
else
{
// Exact size match or too small overhead for a free entry.
std::size_t sz = (*e)->size;
free_entry *next = (*e)->next;
x = reinterpret_cast <allocated_entry *> (*e);
new (x) allocated_entry;
x->size = sz;
*e = next;
}
return &x->data;
}
void pool::free (void *data)
{
__gnu_cxx::__scoped_lock sentry(emergency_mutex);
allocated_entry *e = reinterpret_cast <allocated_entry *>
(reinterpret_cast <char *> (data) - offsetof (allocated_entry, data));
std::size_t sz = e->size;
if (!first_free_entry)
{
// If the free list is empty just put the entry there.
free_entry *f = reinterpret_cast <free_entry *> (e);
new (f) free_entry;
f->size = sz;
f->next = NULL;
first_free_entry = f;
}
else if (reinterpret_cast <char *> (e) + sz
== reinterpret_cast <char *> (first_free_entry))
{
// Check if we can merge with the first free entry being right
// after us.
free_entry *f = reinterpret_cast <free_entry *> (e);
new (f) free_entry;
f->size = sz + first_free_entry->size;
f->next = first_free_entry->next;
first_free_entry = f;
}
else
{
// Else search for a free item we can merge with at its end.
free_entry **fe;
for (fe = &first_free_entry;
(*fe)->next
&& (reinterpret_cast <char *> ((*fe)->next)
> reinterpret_cast <char *> (e) + sz);
fe = &(*fe)->next)
;
if (reinterpret_cast <char *> (*fe) + (*fe)->size
== reinterpret_cast <char *> (e))
/* Merge with the freelist entry. */
(*fe)->size += sz;
else
{
// Else put it after it which keeps the freelist sorted.
free_entry *f = reinterpret_cast <free_entry *> (e);
new (f) free_entry;
f->size = sz;
f->next = (*fe)->next;
(*fe)->next = f;
}
}
}
bool pool::in_pool (void *ptr)
{
char *p = reinterpret_cast <char *> (ptr);
return (p > arena
&& p < arena + arena_size);
}
pool emergency_pool;
}
extern "C" void *
__cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
{
void *ret;
thrown_size += sizeof (__cxa_refcounted_exception);
ret = malloc (thrown_size);
if (!ret)
ret = emergency_pool.allocate (thrown_size);
if (!ret)
std::terminate ();
memset (ret, 0, sizeof (__cxa_refcounted_exception));
return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
}
extern "C" void
__cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
{
char *ptr = (char *) vptr - sizeof (__cxa_refcounted_exception);
if (emergency_pool.in_pool (ptr))
emergency_pool.free (ptr);
else
free (ptr);
}
extern "C" __cxa_dependent_exception*
__cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
{
__cxa_dependent_exception *ret;
ret = static_cast<__cxa_dependent_exception*>
(malloc (sizeof (__cxa_dependent_exception)));
if (!ret)
ret = static_cast <__cxa_dependent_exception*>
(emergency_pool.allocate (sizeof (__cxa_dependent_exception)));
if (!ret)
std::terminate ();
memset (ret, 0, sizeof (__cxa_dependent_exception));
return ret;
}
extern "C" void
__cxxabiv1::__cxa_free_dependent_exception
(__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
{
if (emergency_pool.in_pool (vptr))
emergency_pool.free (vptr);
else
free (vptr);
}