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diff --git a/external/glim/raii.hpp b/external/glim/raii.hpp
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+++ b/external/glim/raii.hpp
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+#include <functional>
+namespace glim {
+
+// http://stackoverflow.com/questions/2121607/any-raii-template-in-boost-or-c0x/
+
+/// RAII helper. Keeps the functor and runs it in the destructor.
+/// Example: \code auto unmap = raiiFun ([&]() {munmap (fd, size);}); \endcode
+template<typename Fun> struct RAIIFun {
+  Fun _fun;
+  RAIIFun (RAIIFun&&) = default;
+  RAIIFun (const RAIIFun&) = default;
+  template<typename FunArg> RAIIFun (FunArg&& fun): _fun (std::forward<Fun> (fun)) {}
+  ~RAIIFun() {_fun();}
+};
+
+/// The idea to name it `finally` comes from http://www.codeproject.com/Tips/476970/finally-clause-in-Cplusplus.
+/// Example: \code finally unmap ([&]() {munmap (fd, size);}); \endcode
+typedef RAIIFun<std::function<void(void)>> finally;
+
+/// Runs the given functor when going out of scope.
+/// Example: \code
+///   auto closeFd = raiiFun ([&]() {close (fd);});
+///   auto unmap = raiiFun ([&]() {munmap (fd, size);});
+/// \endcode
+template<typename Fun> RAIIFun<Fun> raiiFun (const Fun& fun) {return RAIIFun<Fun> (fun);}
+
+/// Runs the given functor when going out of scope.
+/// Example: \code
+///   auto closeFd = raiiFun ([&]() {close (fd);});
+///   auto unmap = raiiFun ([&]() {munmap (fd, size);});
+/// \endcode
+template<typename Fun> RAIIFun<Fun> raiiFun (Fun&& fun) {return RAIIFun<Fun> (std::move (fun));}
+
+}