CODEWITHSUNDEEP
windowssemaphore
ajay bidari
ajay bidari

Reputation: 723

what is the size of windows semaphore object?

How to find size of a semaphore object in windows?

I tried using sizeof() but we cannot give name of the sempahore object as an argument to sizeof. It has to be the handle. sizeof(HANDLE) gives us the size of handle and not semaphore.

Upvotes: 2

Views: 570

Answers (2)

xanatos
xanatos

Reputation: 111860

It's something "hidden" from you. You can't say how big it is. And it's a kernel object, so it probably doesn't even live in your address space. It's like asking "how big is the Process Table?", or "how many MB is Windows wasting?".

I'll add that I have made a small test on my Windows 7 32 bits machine: 100000 kernel semaphores (with name X{number} with 0 <= number < 100000)) : 4 mb of kernel memory and 8 mb of user space (both measured with Task Manager). It's about 40 bytes/semaphore in kernel space and 80 bytes/semaphore in user space! (this in Win32... In 64 bits it'll probably double)

Upvotes: 3

IronMensan
IronMensan

Reputation: 6831

This what is known as an "opaque handle.". There is no way to know how big it really is, what it contains or how any of the functions work internally. This gives Microsoft the ability to completely rewrite the implementation with each new version of Windows if they want to without worrying about breaking existing code. It's a similar concept to having a public and private interface to a class. Since we are not working on the Windows kernel, we only get to see the public interface.

Update:

It might be possible to get a rough idea of how big they are by creating a bunch and monitoring what happens to your memory usage in Process Explorer. However, since there is a good chance that they live in the kernel and not in user space, it might not show up at all. In any case, there are no guarantees about any other version of Windows, past or future, including patches/service packs.

Upvotes: 4

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