In a singleton class (in my case C++), if one method is called more than once, will the locals be on the stack?

i have singleton class , when calling one of the singleton methods more then once in开发者_如何学运维 the same time , and this method has local variables . does each method call of the singleton gets its own private stack , do i need to worry about sharing/mixing local variable data between calls ?

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Using local variables in a class method (not important whether it is a singleton) is no different from using local variables in a regular function. The local variables will not get mixed up.

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No, you do not need to worry about that. To correct your terminology: "does each method call of the singleton gets its own private stack" -- not its own stack but each method call gets its own stack frame so you are alright.

A singleton method is just the same as an ordinary function (in C++). Think of local variables in the same way.

Note that this does not apply to static local variables, which are specifically shared between method calls.

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Each method will gets its own private stack. The only possibility to take care about sharing are static variables inside the class.... but as ur class is singleton that applies to the instance variables of ur class too. Local variables of the method would always be freash in the stack no need to take care about them.

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I'm not sure if you're talking about recursion or multiple thread calls, so I'll assume you mean recursion.

Each time you call the method any local variables that are not declared static are allocated on the stack. The way this works is that each call has it's own stack "frame" When the call is finished, the stack frame is released (and all local variables are destroyed).

So when function foo() is called it's local variables are in a frame on the stack, let's call it frame A. If foo calls itself, another frame is added, let's call it B. During the life of this second call, both frames A and B exist, but A is essentially dormant (usually, the data in A can be modified indirectly, e.g. via pointers). When the second call exits the B frame is released and the A frame becomes active again. Finally, when the top call is finished, the A frame goes away.

Since there is a limited amount of stack space, you have to be careful not to create more frames than the stack can hold. If you do, the stack is said to "overflow".