Quoted from Microsoft Website: reinterpret_cast Operator-优快云博客

本文详细介绍了C++中reinterpret_cast操作符的用法及其潜在风险。该操作符允许开发者将一种类型的指针转换为另一种类型的指针，并能在整数类型与指针类型之间相互转换。虽然这种操作符在低级别编程中有其用途，但不恰当的使用可能会导致不安全的情况。文章还通过一个实际例子——哈希函数来展示如何正确地使用这一操作符。

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reinterpret_cast:

Allows any pointer to be converted into any other pointer type. Also allows any integral type to be converted into any pointer type and vice versa.

form:

reinterpret_cast < type-id > ( expression )

Misuse of the reinterpret_cast operator can easily be unsafe. Unless the desired conversion is inherently low-level, you should use one of the other cast operators.

The reinterpret_cast operator can be used for conversions such aschar* to int*, or One_class* to Unrelated_class*, which are inherently unsafe.

The result of a reinterpret_cast cannot safely be used for anything other than being cast back to its original type. Other uses are, at best, nonportable.

The reinterpret_cast operator cannot cast away theconst, volatile, or__unaligned attributes. See const_cast Operator for information on removing these attributes.

The reinterpret_cast operator converts a null pointer value to the null pointer value of the destination type.

One practical use of reinterpret_cast is in a hash function, which maps a value to an index in such a way that two distinct values rarely end up with the same index.

// expre_reinterpret_cast_Operator.cpp
// compile with: /EHsc
#include <iostream>

// Returns a hash code based on an address
unsigned short Hash( void *p ) {
   unsigned int val = reinterpret_cast<unsigned int>( p );
   return ( unsigned short )( val ^ (val >> 16));
}

using namespace std;
int main() {
   int a[20];
   for ( int i = 0; i < 20; i++ )
      cout << Hash( a + i ) << endl;
}

The reinterpret_cast allows the pointer to be treated as an integral type. The result is then bit-shifted and XORed with itself to produce a unique index (unique to a high degree of probability). The index is then truncated by a standard C-style cast to the return type of the function.

website: http://msdn.microsoft.com/en-us/library/e0w9f63b.aspx