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Delete a NULL pointer is secure.
int* p = NULL;
delete p; // ok, secure
What ist about Handles?
HANDLE h = NULL;
CloseHandle(h); // allowed?
I am reading MSDN but still not sure. It say something about ERROR_INVALID_HANDLE but it is 6L, not NULL.
I come from a destructor of a class, which gives me a C6387 warning Error
if (m_hThread)
WaitForSingleObject(m_hThread, INFINITE);
CloseHandle(m_hThread); // warninig C6387
m_hThread = NULL;
795
In general, CloseHandle invalidates the specified object handle, decrements the object's handle count, and performs object retention checks. After the last handle to an object is closed, the object is removed from the system.
Assuming we find our handle, what do we do with it? Fortunately, there is a trick we can use that allows closing a handle in another process: call DuplicateHandle again, but add the DUPLICATE_CLOSE_SOURCE to close the source handle. Then close our own copy, and that's it!
Generally, an application should call CloseHandleonce for each handle it opens. It is usually not necessary to call CloseHandleif a function that uses a handle fails with ERROR_INVALID_HANDLE, because this error usually indicates that the handle is already invalidated.
It is usually not necessary to call CloseHandle if a function that uses a handle fails with ERROR_INVALID_HANDLE, because this error usually indicates that the handle is already invalidated. However, some functions use ERROR_INVALID_HANDLE to indicate that the object itself is no longer valid.
It say something about ERROR_INVALID_HANDLE but it is 6L, not NULL. Show activity on this post. No. You may not call CloseHandle on a NULL handle.
In general, CloseHandle invalidates the specified object handle, decrements the object's handle count, and performs object retention checks. After the last handle to an object is closed, the object is removed from the system. For a summary of the creator functions for these objects, see Kernel Objects.
No. You may not call CloseHandle on a NULL handle. Look at the documentation for the argument. It says:
hObject [in] A valid handle to an open object.
NULL is not a handle to an open object.
The fact that you get C6387 is precisely because you are passing a "possibly-null" handle to CloseHandle.
You must write the code as:
if (m_hThread) {
WaitForSingleObject(m_hThread, INFINITE);
CloseHandle(m_hThread);
}
(There is no point setting m_hThread to NULL after this - it is going to cease to exist in a very short while).
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