include/llvm/Support/ThreadLocal.h

//===- llvm/Support/ThreadLocal.h - Thread Local Data ------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file declares the llvm::sys::ThreadLocal class.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_THREADLOCAL_H
#define LLVM_SUPPORT_THREADLOCAL_H

#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Threading.h"
#include <cassert>

namespace llvm {
  namespace sys {
    // ThreadLocalImpl - Common base class of all ThreadLocal instantiations.
    // YOU SHOULD NEVER USE THIS DIRECTLY.
    class ThreadLocalImpl {
      typedef uint64_t ThreadLocalDataTy;
      /// Platform-specific thread local data.
      ///
      /// This is embedded in the class and we avoid malloc'ing/free'ing it,
      /// to make this class more safe for use along with CrashRecoveryContext.
      union {
        char data[sizeof(ThreadLocalDataTy)];
        ThreadLocalDataTy align_data;
      };
    public:
      ThreadLocalImpl();
      virtual ~ThreadLocalImpl();
      void setInstance(const void* d);
      void *getInstance();
      void removeInstance();
    };

    /// ThreadLocal - A class used to abstract thread-local storage.  It holds,
    /// for each thread, a pointer a single object of type T.
    template<class T>
    class ThreadLocal : public ThreadLocalImpl {
    public:
      ThreadLocal() : ThreadLocalImpl() { }

      /// get - Fetches a pointer to the object associated with the current
      /// thread.  If no object has yet been associated, it returns NULL;
      T* get() { return static_cast<T*>(getInstance()); }

      // set - Associates a pointer to an object with the current thread.
      void set(T* d) { setInstance(d); }

      // erase - Removes the pointer associated with the current thread.
      void erase() { removeInstance(); }
    };
  }
}

#endif