Is there performance loss if change template parameter from function pointer to std::function?

Asked Oct 20 '16 at 23:03

Active Oct 20 '16 at 23:03

Viewed 111 times

Function object could be any of the 3 : lambda expression, functor (classes overloaded operator ()), and std::function.

I understand that in a template, if a parameter type is defined as std::function, it could take parameter of any of the three.

for example, a type defined by typedef std::function<bool(Logger&)> FilterStdFunction; will be more general than typedef bool(*FilterFunctionPointer)(Logger&); when used as a template parameter.

But would there be performance loss? such as impossible to inline it?

asked Oct 20 '16 at 23:03

athos

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Yes. No inlining, mandatory dynamic dispatch, and possibly dynamic allocation. – Kerrek SB Oct 20 '16 at 23:04
@KerrekSB could you pls give more reason for that or quote some source explaining the details a bit more? – athos Oct 20 '16 at 23:05
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Before using `std::function` [read this](http://stackoverflow.com/q/11628765/1012936) – milleniumbug Oct 20 '16 at 23:12
@athos: well, think about what `std::function` does, and how you would necessarily need to structure it. – Kerrek SB Oct 20 '16 at 23:16
@kerrecksb std function *can* be inlined, it is just harder. – Yakk - Adam Nevraumont Oct 20 '16 at 23:50
@athos have a very simple program and a great compiler who devirtualizes and inlines the function pointers? – Yakk - Adam Nevraumont Oct 21 '16 at 00:10
ok... depending on vendor.. – athos Oct 21 '16 at 00:13

Is there performance loss if change template parameter from function pointer to std::function?

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