I didn't mean C is not fast or not faster than other languages. It's still the fastest one I believe.
What I meant is undefined behaviors allow compilers to optimize in a way that would not be possible otherwise. So, it might be a deliberate decision back then, to leverage performance. I don't know, just an idea.
I agree but I didn't consider these while saying C is the fastest. These are not "general purpose", like you don't write your db, browser, http server or game engine with these.
Also, theoretical performance is overrated. Almost all the things that lends themselves to speed make code brittle and incapable of future modification.
Once you’ve got your C code doing safety checks with data types that won’t break under the littlest change, the code becomes much slower than code golf would suggest. A common example is passing void pointers everywhere. You either check every call every time (aka dynamic typing) or rush everything on the idea that the programmer understands the system completely and never forgets or messes up. Better types give you all the speed AND all the safety here.
What I meant is undefined behaviors allow compilers to optimize in a way that would not be possible otherwise. So, it might be a deliberate decision back then, to leverage performance. I don't know, just an idea.