提取 2 个类型转换为 (void*) 的指针
我试图传递 2 个指针作为另一个类型转换为 (void*) 的函数的争论 如何在最终函数中分离这两个？
例子：
class Backgrounder{
public:
MESSAGE_QUEUE* m_pMsgQueue;
LockSection* m_pLc;
static void __cdecl Run( void* args){
MESSAGE_QUEUE* s_pMsgQueue = (MESSAGE_QUEUE*)args[0]; // doesn't work
LockSection* s_pLc = (LockSection*)args[1]; // doesn't work
}
Backgrounder(MESSAGE_QUEUE* pMsgQueue,LockSection* pLc) {
m_pMsgQueue = pMsgQueue;
m_pLc = pLc;
_beginthread(Run,0,(void*)(m_pMsgQueue,m_pLc));
}
~Backgrounder(){ }
};
I'm trying to pass 2 pointers as an arguement for another function typecasted into (void*)
How do I seperate those two in the final function?
Example:
class Backgrounder{
public:
MESSAGE_QUEUE* m_pMsgQueue;
LockSection* m_pLc;
static void __cdecl Run( void* args){
MESSAGE_QUEUE* s_pMsgQueue = (MESSAGE_QUEUE*)args[0]; // doesn't work
LockSection* s_pLc = (LockSection*)args[1]; // doesn't work
}
Backgrounder(MESSAGE_QUEUE* pMsgQueue,LockSection* pLc) {
m_pMsgQueue = pMsgQueue;
m_pLc = pLc;
_beginthread(Run,0,(void*)(m_pMsgQueue,m_pLc));
}
~Backgrounder(){ }
};
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评论（3）
您应该创建一个以这两种指针类型作为成员的
struct，并传递一个指向该结构的指针。You should create a
structwith these two pointer types as members, and pass a pointer to that around.表达式
(m_pMsgQueue,m_pLc)的作用与您想象的不同；它调用逗号运算符，该运算符仅计算第二个参数。将参数捆绑到一个结构中并传递它。
The expression
(m_pMsgQueue,m_pLc)doesn't do what you think it does; it invokes the comma operator, which simply evaluates to the second argument.Bundle the arguments into a struct and pass that.
您可以将它们包装在一个结构中，并传递一个指向该结构的指针。但要小心，因为该结构不应该在
Backgrounder构造函数本地声明 - 这会导致未定义的行为，因为在启动它的函数之后线程可能仍在运行终止。它应该是动态分配的、静态类成员或全局变量。实际上，我会传递
this指针，因为您本质上希望能够访问Run函数中对象的字段：当然，您需要确保新创建的Backgrounder对象没有被提前销毁，即线程应该在销毁之前完成。
此外，如果稍后从父线程修改这些字段，您将需要采用适当的同步机制。
You could wrap them together in a struct and pass a pointer to that struct. Be careful though, because that struct should not be declared locally to the
Backgrounderconstructor - that would cause undefined behaviour because the thread may still be running after the function that started it has terminated. It should either be dynamically allocated, astaticclass member, or a global variable.Actually, I would pass the
thispointer since you essentially want to be able to access the fields of the object within theRunfunction:Of course, you'll need to make sure that the newly created
Backgrounderobject is not prematurely destroyed, that is, the thread should be finished before the destruction.Also, if these fields are later modified from the parent thread, you'll need to employ the appropriate synchronisation mechanisms.