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copied!<p>In theory, <code>memcpy</code> might have a <em>slight</em>, <em>imperceptible</em>, <em>infinitesimal</em>, performance advantage, only because it doesn't have the same requirements as <code>std::copy</code>. From the man page of <code>memcpy</code>:</p> <blockquote> <p>To avoid overflows, the size of the arrays pointed by both the destination and source parameters, shall be at least num bytes, <strong>and should not overlap</strong> (for overlapping memory blocks, memmove is a safer approach).</p> </blockquote> <p>In other words, <code>memcpy</code> can ignore the possibility of overlapping data. (Passing overlapping arrays to <code>memcpy</code> is undefined behavior.) So <code>memcpy</code> doesn't need to explicitly check for this condition, whereas <code>std::copy</code> can be used as long as the <code>OutputIterator</code> parameter is not in the source range. Note this is <em>not</em> the same as saying that the source range and destination range can't overlap.</p> <p>So since <code>std::copy</code> has somewhat different requirements, in theory it should be <em>slightly</em> (with an extreme emphasis on <em>slightly</em>) slower, since it probably will check for overlapping C-arrays, or else delegate the copying of C-arrays to <code>memmove</code>, which needs to perform the check. But in practice, you (and most profilers) probably won't even detect any difference.</p> <p>Of course, if you're not working with <a href="http://en.wikipedia.org/wiki/Plain_old_data_structure">PODs</a>, you <em>can't</em> use <code>memcpy</code> anyway.</p>

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