Query the Value of a Semaphore

Have you ever wanted to take a look at the current value of a semaphore whilst debugging your code, but don't want to alter the value of the semaphore by ReleaseSemaphore?

Well, Win32 does not give you the possibilty to get the value, but there is a call in ntdll.dll which allows to query the semaphore. So the 'QuerySemaphore.lib' simply provides a small static lib, which wraps the NtQuerySemaphore call in ntdll.dll.

QuerySemaphore.lib is selfcontained, so your program does not need ntdll.lib to resolve the call to NtQuerySemaphore.

A simple example


	#include "QuerySemaphore.h"

	LONG	Value, v1;

	// Create a semaphore
	HANDLE	Handle = CreateSemaphore(NULL, 4, 10, NULL);

	// Query the content of a semaphore
	QuerySemaphore(Handle, &Value);

	// Acquire Semaphore
	WaitForSingleObject(Handle, INFINITE);
	
	// Query again
	QuerySemaphore(Handle, &Value);