std ::函数为sighandler_t [英] std::function as sighandler_t

问题描述

如何指定lambda，std :: bind结果或任何其他std :: function作为unix信号函数的参数?

How to specify lambda, std::bind result or any other std::function as argument for unix signal function?

我正在尝试以下

std::function<void(int)> handler1 = std::bind(&cancellation_token::cancel, &c);
std::function<void(int)> handler2 = [&c](int) { c.cancel(); };

但是它不起作用，因为两者都

but it doesn't work, because both

handler1.target<void(int)>()

和

handler2.target<void(int)>()

return null

如果我使用自由函数指针初始化处理程序，它将起作用

It works if I initialize handler with free function pointer

void foo(int) { ... }
std::function<void(int)> handler = foo;

但这绝对没用.我需要捕获一些局部变量，因此需要bind或lambda.

but this is absolutely useless. I need to capture some local variables, so I need either bind or lambda.

实际上，我知道为什么它不起作用.文档说，如果target_type() == typeid(T)，target函数将返回指向存储函数的指针，否则返回空指针.我不知道如何使它工作.

Actually I understand why it doesn't work. Documentation says that target function returns a pointer to the stored function if target_type() == typeid(T), otherwise a null pointer. I don't understand how to make it work.

有什么建议吗?

推荐答案

由于它是由bind或具有捕获数据的lambda构造的，因此您无法将其转换为自由函数，因为target函数由typeid起作用，std::function会将其保存在运行时中，而不是将function用作模板的类型T.对于std::bind，它将是某种库类型，对于lambda，它将是某种未命名类型.

Since it's constructed by bind, or lambda with captured-data, you cannot convert it to free function, since target function works by typeid, std::function saves it in runtime, not for type T, with which function is templated. For std::bind it will be some library-type and for lambda it will be some unnamed type.

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