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copied!<p>As Vlad and Alf commented, <code>std::string().swap(the_string)</code> is the C++98 way to release <code>the_string</code>'s capacity, and <code>the_string.shrink_to_fit()</code> is the C++11 way.</p> <p>As to why <code>clear()</code>, <code>erase()</code>, <code>resize()</code>, etc. don't do it, this is an optimization to reduce allocations when you use a string over and over. If <code>clear()</code> freed the string's capacity, you'd generally have to reallocate a similar amount of space on the next iteration, which would take some time the implementation can save by keeping the capacity around. This implementation isn't guaranteed by the standard, but it's very common in implementations.</p> <p><code>reserve()</code> is documented with</p> <blockquote> <p>Calling reserve() with a res_arg argument less than capacity() is in effect a non-binding shrink request. A call with res_arg <= size() is in effect a non-binding shrink-to-fit request.</p> </blockquote> <p>which implies that implementations are more likely to release the capacity on a <code>reserve()</code> call. If I'm reading them right, <a href="http://llvm.org/viewvc/llvm-project/libcxx/trunk/include/string?view=markup" rel="nofollow">libc++</a> and libstdc++ do release space when you call <code>reserve(0)</code>, but it's plausible for VC++'s library to have made the opposite choice.</p> <p>Edit: As penelope says, <code>std::string</code>'s behavior here tends to be exactly the same as <code>std::vector</code>'s behavior.</p>

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