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POQuestion about the usage of CRITICAL_SECTION
 

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  1. POQuestion about the usage of CRITICAL_SECTION
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    <p>Given the following code,</p> <pre><code>class MyCriticalSection : protected CRITICAL_SECTION { public: MyCriticalSection() { InitializeCriticalSection(this); EnterCriticalSection(this); } ~MyCriticalSection() { LeaveCriticalSection(this); DeleteCriticalSection(this); } }; class MyClass { public: MyClass() : m_Int(0) {} int GetNum() { MyCriticalSection myCriticalSectionA; // LockA return m_Int; } int SetNum(int i) { MyCriticalSection myCriticalSectionB; // LockB m_Int = i; } protected: int m_Int; }; </code></pre> <p>I assume that the above design is correct, please correct me if you find some errors. The usage of LockA has two capabilities: 1> it prevents the function GetNum from being call at the same time by more than one thread. 2> it prevents the functions GetNum and SetNum from accessing the m_Int at the same time.</p> <p>Here is my question: The variables myCriticalSectionA and myCriticalSectionB are two different instances of class MyCriticalSection. Why they can collaborate with each other so that the lock mechanism work as expect?</p> <p>My guess is that somehow the CRITICAL_SECTION has some static flag so that different instances of it can communicate each other.</p> <p>Please correct me if I am wrong.</p> <p>==== Update ====</p> <pre><code>class MyCriticalSection : protected CRITICAL_SECTION { public: MyCriticalSection() { InitializeCriticalSection(this); } ~MyCriticalSection() { DeleteCriticalSection(this); } void Lock() { EnterCriticalSection(this); } void UnLock() { LeaveCriticalSection(this); } }; class MyClass { public: MyClass() : m_Int(0) {} int GetNum() { m_Lock.Lock(); // do something here m_Lock.UnLock(); return m_Int; } int SetNum(int i) { m_Lock.Lock(); m_Int = i; m_Lock.UnLock(); } protected: int m_Int; MyCriticalSection m_Lock; }; </code></pre> <p>Thank you</p>
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    1. COWhat makes you think that the two instances are actually "collaborating" (and that the code is correct)?
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    2. CO@aix, I think I incorrectly made assumption that this critical section is similar as what Java provides as a synchronized method. -- thx
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