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    <p>First, of course: the pointer is guaranteed to be aligned in the first case (by §5.3.4/10 and §3.7.4.1/2), and may be correctly aligned in both cases. (Obviously, if <code>sizeof(int) == 1</code>, but even when this is not the case, an implementation doesn't necessarily have alignment requirements.) </p> <p>And to make things clear: your casts are all <code>reinterpret_cast</code>.</p> <p>Beyond that, this is an interesting question, because as far as I can tell, there is no difference in the two casts, as far as the standard is concerned. The results of the conversion are unspecified (according to §5.2.10/7); you're not even guaranteed that converting it back into a <code>char*</code> will result in the original value. (It obviously won't, for example, on machines where <code>int*</code> is smaller than a <code>char*</code>.)</p> <p>In practice, of course: the standard requires that the return value of <code>new char[N]</code> be sufficiently aligned for any value which may fit into it, so you are guaranteed to be able to do:</p> <pre><code>intPtr = new (charPtr) int; </code></pre> <p>Which has exactly the same effect as your cast, given that the default constructor for <code>int</code> is a no-op. (And assuming that <code>sizeof(int) &lt;= 42</code>.) So it's hard to imagine an implementation in which the first part fails. You should be able to use the <code>intPtr</code> just like any other legally obtained <code>intPtr</code>. And the idea that converting it back to a <code>char*</code> would somehow result in a different value from the original <code>char*</code> seems preposterous.</p> <p>In the second part, all bets are off: you definitely can't dereference the pointer (unless your implementation guarantees otherwise), and it's also quite possible that converting it back to <code>char*</code> results in something different. (Imagine a word addressed machine, for example, where converting a <code>char*</code> to an <code>int*</code> rounds up. Then converting back would result in a <code>char*</code> which was <code>sizeof(int)</code> higher than the original. Or where an attempt to convert a misaligned pointer always resulted in a null pointer.)</p>
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