Pre-compiled headers, binary libraries, avoid header only libraries, if lucky to be on latest clang/VC++, modules.

pch are not standard

Modules support was added recently, and I don't think most libraries or cmake support it yet, and I don't really see tutorial about good practices for modules, especially when it comes down to speeding up compilation.

Also modules do not really speed up compilation that much, apparently, or I have not seen benchmarks, maybe because modules are not well supported yet?

Modules are great in theory, but I am not sure they are usable in 100% of cases, especially with all the existing code that is out there?

C++ is not slow to compile. The Standard Library is.

C++ is just slow to compile. With the standard library it is much worse. The problem is that with C++ you're not getting as much encapsulation as you would in C unless you do extra work that also has a performance hit (pimpl). This means that C++ code often has to recompile a whole lot more than C code does when doing incremental compilation in my experience.

This is just not true. There's nothing that makes C++ inherently slow to compile.

PImpl doesn't need to have a performance hit as you can implement it with a local fixed-sized buffer that's not heap-allocated.

You can also design your C++ codebase exactly as you would in C, so there's literally no reason why you'll need to recompile more in one language compared to the other.

C++ is not context free.

A quick google "c++ grammar" will give you clues that C++ is not you average language. Templates are also turing complete, and probably not trivial to parse.

Of course I am not talking about C++98, but C++14, 17, etc, which add significant stuff.