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- // -*- C++ -*- Allocate exception objects.
- // Copyright (C) 2001-2022 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 __gnu_cxx
- {
- void __freeres();
- }
- namespace
- {
- // A fixed-size heap, variable size object allocator
- class pool
- {
- public:
- pool();
- _GLIBCXX_NODISCARD 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;
- friend void __gnu_cxx::__freeres();
- };
- 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))
- {
- // Split 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
- || (reinterpret_cast <char *> (e) + sz
- < reinterpret_cast <char *> (first_free_entry)))
- {
- // If the free list is empty or the entry is before the
- // first element and cannot be merged with it add it as
- // the first free entry.
- free_entry *f = reinterpret_cast <free_entry *> (e);
- new (f) free_entry;
- f->size = sz;
- f->next = first_free_entry;
- 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 we can merge the next block into us do so and continue
- // with the cases below.
- if (reinterpret_cast <char *> (e) + sz
- == reinterpret_cast <char *> ((*fe)->next))
- {
- sz += (*fe)->next->size;
- (*fe)->next = (*fe)->next->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;
- }
- namespace __gnu_cxx
- {
- void
- __freeres()
- {
- if (emergency_pool.arena)
- {
- ::free(emergency_pool.arena);
- emergency_pool.arena = 0;
- }
- }
- }
- 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);
- }
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