[PD] [offtopic] Re: That C++ is slower thing again

[Larry Troxler]

On Sunday 23 November 2003 17:12, mark wrote:
> This is an argument that is utterly ridiculous in this day and age.
>
> I used to have it with the box coders (the guys that wrote
> emebeded and onboard code) when I worked for a racing car
> firm many years ago. Then, they had a point.

Strange. "Many years ago" I coded for EPROM as well, and weirdly, it was the 
corss-compiler vendors that were slow to offer C++, while I was constantly 
bugging them about it. This is kind of interesting, since you apparently knew 
embedded systems programmers that didn't want C++. Perhaps they were really 
hardware engineers who soft of evolved into doing software, and even the 
concept of using C and not assembler was very experimental in their minds.

Even though stuff like dynamic allocation was irrelevant at the time, I sure 
could have used the syntactical, organizational help that C++ offers, when 
doing those 128KB - 512KB ROMs.  I think that paradoxically, it was because I 
was so size and speed conscious, that I was in tune with what the compilers 
were generating, that I realized that using C++ would have been a great 
design-time convenience, whithout imposing run-time cost. 

> On a modern PC
> loaded with a busy operating system (linux suffers less here
> perhaps  than windows but there is still a lot going on) I defy
> ANYONE to detect a difference between what is essentially
> a few extra pointer de-references.
>

I think the misconception these days arises simply because the larger, and 
hence slower, the project, the more likely it is that it uses C++ and not 
just C. IOW there's some causality confusion taking effect.

Certainly (I hope!) nobody is still arguing that the virtual member function 
mechanism is slowing things down!


> yes - C++ is marginally slower than C but unless you are working
> in a tiny amount of memory on low power processor I doubt it will
> effect you at all. Even the box coders would win their arguments
> based on memory usage against speed more often than not
>

No, I disagree with you here. C++ is not "marginally slower than C;". But that 
statement is of course quite vague - to be more precise, you would really 
have to define the environment surrounding that statement, for your assertion 
to have any meaning. Without defining parameters, it's equally valid to say 
that C++ is slower than C, the same as C, or in fact, is faster than C.

But for most practical purposes, C++ is the same as C as far as run-time 
performance is concerned. At least, from a theoretical point of view, this 
_must_ be true - both C and C++ are compiled, statically typed, languages. 
Maybe some computer science graduate could verify or refute this conjecture.

Larry