Indeed, with lambdas you don't need to deal with locks outliving the underlying object (though I think std::unique_lock has the same issue with the underlying m

Indeed, with lambdas you don't need to deal with locks outliving the underlying object (though I think std::unique_lock has the same issue with the underlying mutex?) The downside with lambdas is that you cannot lock across function boundaries e.g. give ownership of a lock to the caller. There's a similar tradeoff for all "context managers" (in Python parlance) where you could either CPS your way around the control flow (the lambda approach) or use c++'s RAII mechanism. My impression is that RAII feels a bit more idiomatic and puts the burden on library writers instead of users.