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GCC will insert various calls to pthread functions when compiling C++ code with static initializers, even when the user doesn't link their program against libpthread explicitly. This is used to make static initializers thread-safe, e.g. when building a library that does not itself use thread functionality and thus does not link against libpthread - but is intended to be used with other code that does use libpthread explicitly. This makes these symbols available in libc.
130 lines
4.2 KiB
C++
130 lines
4.2 KiB
C++
/*
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* Copyright (c) 2021, the SerenityOS developers.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/Atomic.h>
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#include <LibPthread/pthread.h>
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#include <unistd.h>
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#ifndef _DYNAMIC_LOADER
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extern "C" {
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static constexpr int max_keys = PTHREAD_KEYS_MAX;
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struct KeyTable {
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KeyDestructor destructors[max_keys] { nullptr };
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int next { 0 };
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pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
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};
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struct SpecificTable {
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void* values[max_keys] { nullptr };
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};
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static KeyTable s_keys;
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__thread SpecificTable t_specifics;
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int __pthread_key_create(pthread_key_t* key, KeyDestructor destructor)
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{
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int ret = 0;
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__pthread_mutex_lock(&s_keys.mutex);
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if (s_keys.next >= max_keys) {
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ret = EAGAIN;
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} else {
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*key = s_keys.next++;
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s_keys.destructors[*key] = destructor;
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ret = 0;
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}
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__pthread_mutex_unlock(&s_keys.mutex);
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return ret;
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}
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int pthread_key_create(pthread_key_t*, KeyDestructor) __attribute__((weak, alias("__pthread_key_create")));
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int __pthread_key_delete(pthread_key_t key)
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{
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if (key < 0 || key >= max_keys)
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return EINVAL;
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__pthread_mutex_lock(&s_keys.mutex);
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s_keys.destructors[key] = nullptr;
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__pthread_mutex_unlock(&s_keys.mutex);
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return 0;
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}
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int pthread_key_delete(pthread_key_t) __attribute__((weak, alias("__pthread_key_delete")));
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void* __pthread_getspecific(pthread_key_t key)
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{
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if (key < 0)
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return nullptr;
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if (key >= max_keys)
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return nullptr;
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return t_specifics.values[key];
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}
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void* pthread_getspecific(pthread_key_t) __attribute__((weak, alias("__pthread_getspecific")));
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int __pthread_setspecific(pthread_key_t key, const void* value)
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{
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if (key < 0)
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return EINVAL;
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if (key >= max_keys)
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return EINVAL;
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t_specifics.values[key] = const_cast<void*>(value);
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return 0;
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}
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int pthread_setspecific(pthread_key_t, const void*) __attribute__((weak, alias("__pthread_setspecific")));
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void __pthread_key_destroy_for_current_thread()
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{
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// This function will either be called during exit_thread, for a pthread, or
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// during global program shutdown for the main thread.
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__pthread_mutex_lock(&s_keys.mutex);
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size_t num_used_keys = s_keys.next;
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// Dr. POSIX accounts for weird key destructors setting their own key again.
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// Or even, setting other unrelated keys? Odd, but whatever the Doc says goes.
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for (size_t destruct_iteration = 0; destruct_iteration < PTHREAD_DESTRUCTOR_ITERATIONS; ++destruct_iteration) {
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bool any_nonnull_destructors = false;
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for (size_t key_index = 0; key_index < num_used_keys; ++key_index) {
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void* value = exchange(t_specifics.values[key_index], nullptr);
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if (value && s_keys.destructors[key_index]) {
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any_nonnull_destructors = true;
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(*s_keys.destructors[key_index])(value);
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}
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}
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if (!any_nonnull_destructors)
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break;
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}
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__pthread_mutex_unlock(&s_keys.mutex);
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}
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}
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#endif
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