Sudarshan Gaikaiwari » Software http://www.sudarshan.org/blog There will be some changes made Wed, 18 Nov 2009 18:21:37 +0000 http://wordpress.org/?v=2.8 en hourly 1 C++ function resolution http://www.sudarshan.org/blog/2007/05/cplusplu-function-resolution/ http://www.sudarshan.org/blog/2007/05/cplusplu-function-resolution/#comments Thu, 24 May 2007 13:37:53 +0000 Sudarshan http://www.sudarshan.org/blog/2007/05/24/c-function-resolution/ I earn my living writing C++ code these days. Everyday I learn something new and interesting about this language. Many languages have a simple core, if you understand a few basic principles you can understand how most of the language works. C++ has a lot of esoteric features and no guiding principles that to borrow a term from human computer interaction allow the programmer to develop expectations. I think the reasons for this are historical.
Reading Lippman’s Inside the C++ Object model and Stroustrup’s Design and Evolution of the C++ Programming language I am amazed by how much attention was paid to match C in performance

f()
{
   a.f()      // resolved at compile time (not polymorphic)
   p->f()     // resolved at runtime
}

The static resolution is a feature. The C++ compiler writers were trying to avoid the single instruction cost of vptr dereferencing. For a programmer this means that just marking a function as virtual does not mean that the most overriden version will be invoked. To ensure that every invocation must also be polymorphic. Also there is a principle at work here. You do not have to pay for what you do not use.

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