c++ - thread_local 变量何时以及如何初始化和销毁​​？

Question

在我的代码中使用 thread_local 之前，我想更好地理解它。

比方说，我声明

thread_local myclass value;

这将为每个使用 myclass 的线程创建 value 的新实例？当线程退出时会发生什么？实例会被释放还是会保留在内存中的某个地方？什么时候会被称为析构函数？
thread_local 是否锁定构造函数，以便在任何时候都只能调用一个？

Answer 1

[basic.stc.thread]/1 All variables declared with the thread_local keyword have thread storage duration. The storage for these entities shall last for the duration of the thread in which they are created. There is a distinct object or reference per thread, and use of the declared name refers to the entity associated with the current thread.

[basic.stc.thread]/2 A variable with thread storage duration shall be initialized before its first odr-use (6.2) and, if constructed, shall be destroyed on thread exit.

不，构造函数调用没有自动同步。不需要，因为只有一个线程可以尝试构造给定的线程本地对象。