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    <p>Generally, when lambda is used for "downward" closure, you can convert a c++ lambda to a clang block by converting:</p> <pre><code>[&amp;](int i) { return i; } </code></pre> <p>to:</p> <pre><code>^(int i) { return i; } </code></pre> <p>There is still some subtle differences. Clang's blocks only capture C++ classes by const. I don't know if this includes C++ POD types too.</p> <p>Finally, if "upward" closure is needed, then the two diverge drastically. Clang's blocks require variables captured to be annotated with <code>__block</code>, which the compiler will allocate it on the heap. Whereas, in C++, the way the lambda captures, needs to be decided based on the lifetime of the object.(That is by value making a copy or by reference). </p> <p>Also in C++, copying the closure is handle automatically by the copy-constructor mechanism in C++. However, with clang's block, <code>Block_copy</code> and <code>Block_release</code> need to be called to handle the copying of the block. A simple wrapper can be written in C++ to handle this. For example:</p> <pre><code>typedef void (^simple_block)(void); class block_wrapper { simple_block block; public: block_wrapper (const simple_block&amp; x) : block(Block_copy(x)) {} void operator() () const { block(); } block_wrapper(const block_wrapper&amp; rhs) : block(Block_copy(rhs.block)) {} block_wrapper&amp; operator=(const block_wrapper&amp; rhs) { if (this != &amp;rhs) { Block_release(this-&gt;block); this-&gt;block = Block_copy(rhs.block); } return *this; } ~block_wrapper () { Block_release(this-&gt;block); } }; </code></pre>
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