Yes, C++ is unquestionably slower than C when you use it to the full potential and when you program the C++ way! A lot of people still program in C++ using the C style. I've used C++ for 7 yeas and have plenty of experience with it and I've seen its slowness in many instances. Main thing to avoid with C++ is virtual methods. Once you understand how they're implemented, you will understand why (hint: vtables).
No offense, but did you carefully read what Jay said? C and C++ is essentially same language, extended with OO+templates. And you can implement virtual method call in C as well.
I would even argue that C++ is faster than C because latest compiler optimization techniques and modern approach to templatized designs yield very impressive performance not typical for ligher-level languages.
The biggest issue with C++ (as a language) in my opinion is it's total lack of modules. In the end, everything needs to be included into every cpp file.
Speed is certainly not an issue. The only language that gets a chance of beating C/C++ is probably OCaml since it gives more information about your intentions to an optimizer/code generator.
I agree with tx. With C++ you can often avoid what would be virtual method calls in Java / if statements in C by using templates. This lets you effectively inline every function call. It'd be hard to do this in a clean way in C.
Main thing to avoid with C++ is virtual methods. Once you understand how they're implemented, you will understand why (hint: vtables).
Why? Are you concerned by the additional pointer dereference? In a tight loop (or other performance critical repetetive code), the vtables for all the derived types and the target piece of code would be sitting in cache already, and the code pointed to by the vtable entry would also be in cache. You have to fetch the object/class/struct instance that you're operating on regardless of whether or not it has a vtable, so that's an unavoidable cost. So I don't see how it's all that expensive. It's just a freaking pointer dereference. I do agree that it can matter in some instances, but I generally have a long list of things to improve before I would try to minimize pointer dereferences on vtables. If you really are having to optimize on such a low level, you'd probably do better to worry about cache hits/misses and data layout in-memory first.
