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// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2005, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
// Author: Paul Menage <opensource@google.com>
//
// Some wrappers for pthread functions so that we can be LD_PRELOADed
// against non-pthreads apps.
//
// This module will behave very strangely if some pthreads functions
// exist and others don't.
#include "config.h"
#include <assert.h>
#include <string.h> // for memcmp
#include <stdio.h> // for __isthreaded on FreeBSD
// We don't actually need strings. But including this header seems to
// stop the compiler trying to short-circuit our pthreads existence
// tests and claiming that the address of a function is always
// non-zero. I have no idea why ...
#include <string>
#include "maybe_threads.h"
#include "base/basictypes.h"
// __THROW is defined in glibc systems. It means, counter-intuitively,
// "This function will never throw an exception." It's an optional
// optimization tool, but we may need to use it to match glibc prototypes.
#ifndef __THROW // I guess we're not on a glibc system
# define __THROW // __THROW is just an optimization, so ok to make it ""
#endif
// These are the methods we're going to conditionally include.
extern "C" {
int pthread_key_create (pthread_key_t*, void (*)(void*))
__THROW ATTRIBUTE_WEAK;
void *pthread_getspecific(pthread_key_t)
__THROW ATTRIBUTE_WEAK;
int pthread_setspecific(pthread_key_t, const void*)
__THROW ATTRIBUTE_WEAK;
int pthread_once(pthread_once_t *, void (*)(void))
ATTRIBUTE_WEAK;
}
#define MAX_PERTHREAD_VALS 16
static void *perftools_pthread_specific_vals[MAX_PERTHREAD_VALS];
static int next_key;
// NOTE: it's similar to bitcast defined in basic_types.h with
// exception of ignoring sizes mismatch
template <typename T1, typename T2>
static T2 memcpy_cast(const T1 &input) {
T2 output;
size_t s = sizeof(input);
if (sizeof(output) < s) {
s = sizeof(output);
}
memcpy(&output, &input, s);
return output;
}
int perftools_pthread_key_create(pthread_key_t *key,
void (*destr_function) (void *)) {
if (pthread_key_create) {
return pthread_key_create(key, destr_function);
} else {
assert(next_key < MAX_PERTHREAD_VALS);
*key = memcpy_cast<int, pthread_key_t>(next_key++);
return 0;
}
}
void *perftools_pthread_getspecific(pthread_key_t key) {
if (pthread_getspecific) {
return pthread_getspecific(key);
} else {
return perftools_pthread_specific_vals[memcpy_cast<pthread_key_t, int>(key)];
}
}
int perftools_pthread_setspecific(pthread_key_t key, void *val) {
if (pthread_setspecific) {
return pthread_setspecific(key, val);
} else {
perftools_pthread_specific_vals[memcpy_cast<pthread_key_t, int>(key)] = val;
return 0;
}
}
static pthread_once_t pthread_once_init = PTHREAD_ONCE_INIT;
int perftools_pthread_once(pthread_once_t *ctl,
void (*init_routine) (void)) {
#ifdef __FreeBSD__
// On __FreeBSD__, calling pthread_once on a system that is not
// linked with -pthread is silently a noop. :-( Luckily, we have a
// workaround: FreeBSD exposes __isthreaded in <stdio.h>, which is
// set to 1 when the first thread is spawned. So on those systems,
// we can use our own separate pthreads-once mechanism, which is
// used until __isthreaded is 1 (which will never be true if the app
// is not linked with -pthread).
static bool pthread_once_ran_before_threads = false;
if (pthread_once_ran_before_threads) {
return 0;
}
if (!__isthreaded) {
init_routine();
pthread_once_ran_before_threads = true;
return 0;
}
#endif
if (pthread_once) {
return pthread_once(ctl, init_routine);
} else {
if (memcmp(ctl, &pthread_once_init, sizeof(*ctl)) == 0) {
init_routine();
++*(char*)(ctl); // make it so it's no longer equal to init
}
return 0;
}
}
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