Have you ever written a statement like:
int *pnValue = new int;
One of my friends asked me what will happen if the above statement is executed. Executed??? I though the code won't even compile. Surprisingly, it compiled and even returned a pointer. Wow, that was something unbelievable.
OK now the question is, what will be size of memory that
The two APIs in Windows that allocates and de allocates the memory are
HeepFree. The CRT functions
free are actually wrappers for the above API. The
delete are again another wrapper around the
free. So whenever you allocate some memory using
new, it will finally reach the
HeapAlloc function. This function is defined as:
LPVOID WINAPI HeapAlloc(
__in HANDLE hHeap,
__in DWORD dwFlags,
__in SIZE_T dwBytes
From the above definition, you can see that the third parameter to this function is the number of BYTES to be allocated. So to find out what "
new int" returns, we can put a break point in the entry point of
HeapAlloc and check the value of
dwBytes (in dis assembly).
When I tried, the
dwBytes turned out to be
1!!! This one byte cannot even hold one
int variable. That means any further operation using such a pointer will possibly crash.
Another interesting thing is "
int *pnValue = new int;" also returns a pointer pointing a memory of
1 byte long.
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