Performance of dynamic_cast?

Question

Before reading the question:
This question is not about how useful it is to use dynamic_cast. Its just about its performance.

I\'ve recently develop

Answer 1

Sorry to say this, but your test is virtually useless for determining whether the cast is slow or not. Microsecond resolution is nowhere near good enough. We're talking about an operation that, even in the worst case scenario, shouldn't take more than, say, 100 clock ticks, or less than 50 nanoseconds on a typical PC.

There's no doubt that the dynamic cast will be slower than a static cast or a reinterpret cast, because, on the assembly level, the latter two will amount to an assignment (really fast, order of 1 clock tick), and the dynamic cast requires the code to go and inspect the object to determine its real type.

I can't say off-hand how slow it really is, that would probably vary from compiler to compiler, I'd need to see the assembly code generated for that line of code. But, like I said, 50 nanoseconds per call is the upper limit of what expect to be reasonable.