You don't really need comptime to be able to inline and unroll a string comparison. This also works in C: https://godbolt.org/z/6edWbqnfT (edit: fixed typo)
To be honest your snippet isn't really C anymore by using a compiler builtin. I'm also annoyed by things like `foo(int N, const char x[N])` which compilation vary wildly between compilers (most ignore them, gcc will actually try to check if the invariants if they are compile time known)
> I haven't really understood the advantage compared to simply running a program at build time.
Since both comptime and runtime code can be mixed, this gives you a lot of safety and control. The comptime in zig emulates the target architecture, this makes things like cross-compilation simply work. For program that generates code, you have to run that generator on the system that's compiling and the generator program itself has to be aware the target it's generating code for.
It also works with memcpy from the library: https://godbolt.org/z/Mc6M9dK4M I just didn't feel like burdening godbolt with an inlclude.
I do not understand your criticism of [N]. This gives compiler more information and catches errors. This is a good thing! Who could be annoyed by this: https://godbolt.org/z/EeadKhrE8 (of course, nowadays you could also define a descent span type in C)
The cross-compilation argument has some merit, but not enough to warrant the additional complexity IMHO. Compile-time computation will also have annoying limitations and makes programs more difficult to understand. I feel sorry for everybody who needs to maintain complex compile time code generation. Zig certainly does it better than C++ but still..
> I do not understand your criticism of [N]. This gives compiler more information and catches errors. This is a good thing!
It only does sane thing in GCC, in other compilers it does nothing and since it's very underspec'd it's rarely used in any C projects. It's shame Dennis's fat pointers / slices proposal was not accepted.
> warrant the additional complexity IMHO
In zig case the comptime reduces complexity, because it is simply zig. It's used to implement generics, you can call zig code compile time, create and return types.
Then the right thing would be to complain about those other compilers. I agree that Dennis' fat pointer proposal was good.
Also in Zig it does not reduce complexity but adds to it by creating an distinction between compile time and run-time. It is only lower complexity by comparing to other implementations of generic which are even worse.
Something like this: https://godbolt.org/z/er9n6ToGP It encapsulates a pointer to an array and a length. It is not perfect because of some language limitation (which I hope we can remove), but also not to bad. One limitation is that you need to pass it a typedef name instead of any type, i.e. you may need a typedef first. But this is not terrible.
Do note that your linked godbolt code actually demonstrates one of the two sub-par examples though.