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    <p>(Quoting the C++03 standard)</p> <p>First there's §12.2/3:</p> <blockquote> <p>When an implementation introduces a temporary object of a class that has a non-trivial constructor (12.1), it shall ensure that a constructor is called for the temporary object. Similarly, the destructor shall be called for a temporary with a non-trivial destructor (12.4). <strong>Temporary objects are destroyed as the last step in evaluating the full-expression (1.9) that (lexically) contains the point where they were created.</strong> This is true even if that evaluation ends in throwing an exception.</p> </blockquote> <p>I believe this is a red herring, because of §1.9/13:</p> <blockquote> <p>[Note: certain contexts in C++ cause the evaluation of a full-expression that results from a syntactic construct other than expression (5.18). For example, in 8.5 one syntax for initializer is</p> <p>&nbsp;&nbsp;&nbsp;&nbsp;<code>( expression-list )</code></p> <p>but the resulting construct is a function call upon a constructor function with expression-list as an argument list; such a function call is a full-expression. For example, in 8.5, another syntax for initializer is</p> <p>&nbsp;&nbsp;&nbsp;&nbsp;<code>= initializer-clause</code></p> <p>but again <strong>the resulting construct might be a function call upon a constructor function with one assignment-expression as an argument; again, the function call is a full-expression</strong>. ]</p> </blockquote> <p>This implies to me that <code>A(b).yield()</code> is itself a full expression, rendering §12.2/3 irrelevant here.</p> <p>Then we get into sequence points -- §1.9/7:</p> <blockquote> <p>Accessing an object designated by a volatile lvalue (3.10), modifying an object, calling a library I/O function, or calling a function that does any of those operations are all side effects, which are changes in the state of the execution environment. Evaluation of an expression might produce side effects. <strong>At certain specified points in the execution sequence called sequence points, all side effects of previous evaluations shall be complete and no side effects of subsequent evaluations shall have taken place.</strong></p> </blockquote> <p>§1.9/16:</p> <blockquote> <p><strong>There is a sequence point at the completion of evaluation of each full-expression.</strong></p> </blockquote> <p>and §1.9/17:</p> <blockquote> <p>When calling a function (whether or not the function is inline), there is a sequence point after the evaluation of all function arguments (if any) which takes place before execution of any expressions or statements in the function body. <strong>There is also a sequence point after the copying of a returned value and before the execution of any expressions outside the function.</strong></p> </blockquote> <p>Putting it all together, <em>I think</em> Clang is right and GCC (and MSVC 2010 SP1) is wrong -- the temporary that holds the result of the expression (whose lifetime is being extended as per §12.2/4) is the <code>bool</code> returned from <code>A::yield()</code>, not the temporary <code>A</code> on which <code>yield</code> is invoked. Taking into account §1.9, there should be a sequence point after the call to <code>A::yield()</code> during which the temporary <code>A</code> is destroyed.</p>
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    1. POWhen exactly is an initializer temporary destroyed?
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