Dear Boost, Review and commentary upon a proposed new Boost object, boost::permit<> is invited. A quick description of their purpose: "Permits come in two variants, consuming and non-consuming. There is always a one-to-one relationship between the granting of a permit and the receiving of that permit, the only difference with the non-consuming variant is that the permit is automatically regranted as soon as it is consumed. This leads to the only API difference to condition variables: permit<consuming=true> provides notify_one() but not notify_all(), whilst permit<consuming=false> provides neither and you will have to use grant() and revoke() instead. When deciding to substitute permits for condition variables, you will need to decide carefully which kind of permit is the correct substitute." "Permit objects are actually very similar to a void promise/future i.e. they act as a reusable promise/future pair but without transporting any value or exception state, just the permission to proceed. This is due to their original design intention, which was as a promise/future equivalent for C11 (see below for their history, and note that the original C API is available in the boost::c_permit namespace and documentation can be found at https://ci.nedprod.com/job/Boost.Thread%20Build%20Documentation/lastSu ccessfulBuild/artifact/boost-trunk/boost/thread/permit/latex/pthread_p ermit_reference.pdf). As such, they can be very useful for situations where a promise/future is too heavy (permits can spin instead of sleep, plus they need not be repeatedly constructed and destructed)." There is lots more detail at their documentation page: https://ci.nedprod.com/job/Boost.Thread%20Build%20Documentation/Boost. Thread_Documentation/libs/thread/doc/html/thread/synchronization/permi t_ref.html Source code of Permit containing fork of Boost.Thread: https://github.com/ned14/thread/tree/permit_object They come with a functional and load soak test suite. They work on Windows, Linux, FreeBSD and I believe OS X. Any other questions do ask. Niall -- Currently unemployed and looking for work in Ireland. Work Portfolio: http://careers.stackoverflow.com/nialldouglas/