gcc/libstdc++-v3/libsupc++/guard.cc

202 lines
5.2 KiB
C++

// Copyright (C) 2002, 2004, 2006 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 2, 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.
// You should have received a copy of the GNU General Public License
// along with GCC; see the file COPYING. If not, write to
// the Free Software Foundation, 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301, USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
// Written by Mark Mitchell, CodeSourcery LLC, <mark@codesourcery.com>
// Thread support written by Jason Merrill, Red Hat Inc. <jason@redhat.com>
#include <bits/c++config.h>
#include <cxxabi.h>
#include <exception>
#include <new>
#include <ext/atomicity.h>
#include <ext/concurrence.h>
// The IA64/generic ABI uses the first byte of the guard variable.
// The ARM EABI uses the least significant bit.
// Thread-safe static local initialization support.
#ifdef __GTHREADS
namespace
{
// A single mutex controlling all static initializations.
static __gnu_cxx::__recursive_mutex* static_mutex;
typedef char fake_recursive_mutex[sizeof(__gnu_cxx::__recursive_mutex)]
__attribute__ ((aligned(__alignof__(__gnu_cxx::__recursive_mutex))));
fake_recursive_mutex fake_mutex;
static void init()
{ static_mutex = new (&fake_mutex) __gnu_cxx::__recursive_mutex(); }
__gnu_cxx::__recursive_mutex&
get_static_mutex()
{
static __gthread_once_t once = __GTHREAD_ONCE_INIT;
__gthread_once(&once, init);
return *static_mutex;
}
}
#ifndef _GLIBCXX_GUARD_TEST_AND_ACQUIRE
inline bool
__test_and_acquire (__cxxabiv1::__guard *g)
{
bool b = _GLIBCXX_GUARD_TEST (g);
_GLIBCXX_READ_MEM_BARRIER;
return b;
}
#define _GLIBCXX_GUARD_TEST_AND_ACQUIRE(G) __test_and_acquire (G)
#endif
#ifndef _GLIBCXX_GUARD_SET_AND_RELEASE
inline void
__set_and_release (__cxxabiv1::__guard *g)
{
_GLIBCXX_WRITE_MEM_BARRIER;
_GLIBCXX_GUARD_SET (g);
}
#define _GLIBCXX_GUARD_SET_AND_RELEASE(G) __set_and_release (G)
#endif
#else /* !__GTHREADS */
#undef _GLIBCXX_GUARD_TEST_AND_ACQUIRE
#undef _GLIBCXX_GUARD_SET_AND_RELEASE
#define _GLIBCXX_GUARD_SET_AND_RELEASE(G) _GLIBCXX_GUARD_SET (G)
#endif /* __GTHREADS */
namespace __gnu_cxx
{
// 6.7[stmt.dcl]/4: If control re-enters the declaration (recursively)
// while the object is being initialized, the behavior is undefined.
// Since we already have a library function to handle locking, we might
// as well check for this situation and throw an exception.
// We use the second byte of the guard variable to remember that we're
// in the middle of an initialization.
class recursive_init_error: public std::exception
{
public:
recursive_init_error() throw() { }
virtual ~recursive_init_error() throw ();
};
recursive_init_error::~recursive_init_error() throw() { }
}
namespace __cxxabiv1
{
static inline int
recursion_push (__guard* g)
{ return ((char *)g)[1]++; }
static inline void
recursion_pop (__guard* g)
{ --((char *)g)[1]; }
static int
acquire (__guard *g)
{
if (_GLIBCXX_GUARD_TEST (g))
return 0;
if (recursion_push (g))
{
#ifdef __EXCEPTIONS
throw __gnu_cxx::recursive_init_error();
#else
// Use __builtin_trap so we don't require abort().
__builtin_trap ();
#endif
}
return 1;
}
extern "C"
int __cxa_guard_acquire (__guard *g)
{
#ifdef __GTHREADS
// If the target can reorder loads, we need to insert a read memory
// barrier so that accesses to the guarded variable happen after the
// guard test.
if (_GLIBCXX_GUARD_TEST_AND_ACQUIRE (g))
return 0;
if (__gthread_active_p ())
{
// Simple wrapper for exception safety.
struct mutex_wrapper
{
bool unlock;
mutex_wrapper() : unlock(true)
{ get_static_mutex().lock(); }
~mutex_wrapper()
{
if (unlock)
static_mutex->unlock();
}
};
mutex_wrapper mw;
if (acquire (g))
{
mw.unlock = false;
return 1;
}
return 0;
}
#endif
return acquire (g);
}
extern "C"
void __cxa_guard_abort (__guard *g)
{
recursion_pop (g);
#ifdef __GTHREADS
if (__gthread_active_p ())
static_mutex->unlock();
#endif
}
extern "C"
void __cxa_guard_release (__guard *g)
{
recursion_pop (g);
_GLIBCXX_GUARD_SET_AND_RELEASE (g);
#ifdef __GTHREADS
if (__gthread_active_p ())
static_mutex->unlock();
#endif
}
}