13.06.2017, 20:08, "Maciej Stachowiak" <[email protected]>: > In case it turns out not to be possible to reduce the number of concepts > (besides eliminating std::function), maybe it would help to change the names > and behaviors of these classes to match better. Function, SharedFunction and > ScopedFunction would have a much more obvious relationship to each other than > Function, SharedTask and ScopedLambda.
Maybe rename Function to UniqueFunction? > > (I'm not sure if the direct assignment from a lambda is an incidental > difference or one that's required by the different ownership semantics.) > > - Maciej > >> On Jun 13, 2017, at 9:34 AM, Filip Pizlo <[email protected]> wrote: >> >> We should have a better story here. Right now the story is too complicated. >> We have: >> >> - ScopedLambda or ScopedLambdaRef if you have a stack-allocated function >> that outlives its user >> - SharedTask if you have a heap-allocated function that you want to share >> and ref-count >> - WTF::Function if you have a heap-allocated function that you want to >> transfer ownership (move yes, copy no) >> - std::function if you have a heap-alloated function that you want to pass >> by copy >> >> Only std::function and WTF::Function do the magic that lets you say: >> >> std::function f = <lambda> >> >> Also, std::function has the benefit that it does copying. None of the >> others do that. >> >> ScopedLambda serves a specific purpose: it avoids allocation. Probably we >> want to keep that one even if we merge the others. >> >> IMO SharedTask has the nicest semantics. I don’t ever want the activation >> of the function to be copied. In my experience I always want sharing if more >> than one reference to the function exists. I think that what we really want >> in most places is a WTF::Function that has sharing semantics like >> SharedTask. That would let us get rid of std::function and SharedTask. >> >> In the current status quo, it’s not always correct to convert std::function >> to the others because: >> >> - Unlike ScopedLambda and SharedTask, std::function has the magic >> constructor that allows you to just assign a lambda to it. >> - Unlike ScopedLambda, std::function is safe if the use is not scoped. >> - Unlike WTF::Function, std::function can be copied. >> >> -Filip >> >>> On Jun 13, 2017, at 9:24 AM, Darin Adler <[email protected]> wrote: >>> >>> I’ve noticed many patches switching us from std::function to WTF::Function >>> recently, to fix problems with copying and thread safety. >>> >>> Does std::function have any advantages over WTF::Function? Should we ever >>> prefer std::function, or should we use WTF::Function everywhere in WebKit >>> where we would otherwise use std::function? >>> >>> — Darin >>> _______________________________________________ >>> webkit-dev mailing list >>> [email protected] >>> https://lists.webkit.org/mailman/listinfo/webkit-dev >> >> _______________________________________________ >> webkit-dev mailing list >> [email protected] >> https://lists.webkit.org/mailman/listinfo/webkit-dev > > _______________________________________________ > webkit-dev mailing list > [email protected] > https://lists.webkit.org/mailman/listinfo/webkit-dev -- Regards, Konstantin _______________________________________________ webkit-dev mailing list [email protected] https://lists.webkit.org/mailman/listinfo/webkit-dev
