/usr/include/kj/threadlocal.h is in libcapnp-dev 0.5.3-2ubuntu1.1.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 | // Copyright (c) 2014, Jason Choy <jjwchoy@gmail.com>
// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
// Licensed under the MIT License:
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#ifndef KJ_THREADLOCAL_H_
#define KJ_THREADLOCAL_H_
#if defined(__GNUC__) && !KJ_HEADER_WARNINGS
#pragma GCC system_header
#endif
// This file declares a macro `KJ_THREADLOCAL_PTR` for declaring thread-local pointer-typed
// variables. Use like:
// KJ_THREADLOCAL_PTR(MyType) foo = nullptr;
// This is equivalent to:
// thread_local MyType* foo = nullptr;
// This can only be used at the global scope.
//
// AVOID USING THIS. Use of thread-locals is discouraged because they often have many of the same
// properties as singletons: http://www.object-oriented-security.org/lets-argue/singletons
//
// Also, thread-locals tend to be hostile to event-driven code, which can be particularly
// surprising when using fibers (all fibers in the same thread will share the same threadlocals,
// even though they do not share a stack).
//
// That said, thread-locals are sometimes needed for runtime logistics in the KJ framework. For
// example, the current exception callback and current EventLoop are stored as thread-local
// pointers. Since KJ only ever needs to store pointers, not values, we avoid the question of
// whether these values' destructors need to be run, and we avoid the need for heap allocation.
#include "common.h"
#if !defined(KJ_USE_PTHREAD_THREADLOCAL) && defined(__APPLE__)
#include "TargetConditionals.h"
#if TARGET_OS_IPHONE
// iOS apparently does not support __thread (nor C++11 thread_local).
#define KJ_USE_PTHREAD_TLS 1
#endif
#endif
#if KJ_USE_PTHREAD_TLS
#include <pthread.h>
#endif
namespace kj {
#if KJ_USE_PTHREAD_TLS
// If __thread is unavailable, we'll fall back to pthreads.
#define KJ_THREADLOCAL_PTR(type) \
namespace { struct KJ_UNIQUE_NAME(_kj_TlpTag); } \
static ::kj::_::ThreadLocalPtr< type, KJ_UNIQUE_NAME(_kj_TlpTag)>
// Hack: In order to ensure each thread-local results in a unique template instance, we declare
// a one-off dummy type to use as the second type parameter.
namespace _ { // private
template <typename T, typename>
class ThreadLocalPtr {
// Hacky type to emulate __thread T*. We need a separate instance of the ThreadLocalPtr template
// for every thread-local variable, because we don't want to require a global constructor, and in
// order to initialize the TLS on first use we need to use a local static variable (in getKey()).
// Each template instance will get a separate such local static variable, fulfilling our need.
public:
ThreadLocalPtr() = default;
constexpr ThreadLocalPtr(decltype(nullptr)) {}
// Allow initialization to nullptr without a global constructor.
inline ThreadLocalPtr& operator=(T* val) {
pthread_setspecific(getKey(), val);
return *this;
}
inline operator T*() const {
return get();
}
inline T& operator*() const {
return *get();
}
inline T* operator->() const {
return get();
}
private:
inline T* get() const {
return reinterpret_cast<T*>(pthread_getspecific(getKey()));
}
inline static pthread_key_t getKey() {
static pthread_key_t key = createKey();
return key;
}
static pthread_key_t createKey() {
pthread_key_t key;
pthread_key_create(&key, 0);
return key;
}
};
} // namespace _ (private)
#elif __GNUC__
#define KJ_THREADLOCAL_PTR(type) static __thread type*
// GCC's __thread is lighter-weight than thread_local and is good enough for our purposes.
#else
#define KJ_THREADLOCAL_PTR(type) static thread_local type*
#endif // KJ_USE_PTHREAD_TLS
} // namespace kj
#endif // KJ_THREADLOCAL_H_
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