So the VTBL would still exist, but for some order od operations (here: Create + someVirtualFunc()) the indirection could/would be optimized out? As the class behind the interface is known from the Create function in this case?
 

-----Ursprüngliche Nachricht-----
Von: Breno Guimarães via Std-Proposals <std-proposals@lists.isocpp.org>
Gesendet: Fr 10.11.2023 02:37
Betreff: Re: [std-proposals] Optimize away VTBL when using single inheritance
An: Std-Proposals <std-proposals@lists.isocpp.org>;
CC: Breno Guimarães <brenorg@gmail.com>;

Hi,

 

Perhaps this should be directed a compiler vendor then?

 

Best Regards,

Breno G

Em qui., 9 de nov. de 2023 22:22, Smith, Jim via Std-Proposals <std-proposals@lists.isocpp.org> escreveu:

Hi All,

Test-driven development (TDD) is my de facto standard for writing software. On some projects I can't use TDD because interfaces introduce VTBL operation into the code. For me this is a serious issue.

 

I've always used C++ interfaces i.e., classes with all pure virtual functions for TDD, especially when implementing a design patterns like Factory.

 

I'm proposing a compiler option that will turn a virtual call through an interface, to a direct call on the object. For example,

 

interface* i = Factory::Create();

 

i->someVirtualFunc();

In cases where single inheritance is used i->someVirtualFunc() would be optimized to a direct call on the object without any VTBL operation.

 

This way the TDD code can use the standard VTBL operations, and in production builds a flag can be set to optimize it away. I can't do this myself without mentioning the concrete type created by the factory but the compiler can make the optimization.

 

 

--James S.

 

 

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