> C++ doesn't take longer to compile if you don't abuse templates.
Surprisingly, this is not true. I've written a C++ file only to realize at the end that I did not use any C++ features. Renaming the file to .c halved the compilation time.
On some compiler toolchains (IIRC MSVC was the main offender) you get a lot more code pulled into your source file when including a C stdlib header (like <stdio.h>) in C++ mode versus C mode. Basically a couple hundred lines in C mode versus thousands of lines in C++ mode.
I agree it shouldn't really matter if there's no C++ features in play, but I suppose third party headers could bite you if they use #ifdef __cplusplus to guard optional C++ extensions on top of their basic C interface. In that case the compiler could be dealing with dramatically more complex code when you build in C++ mode.
Maybe it is similar for the same compiler (but one should check, I suspect C could still be faster), but then there are much more C compilers. For example, TCC is a lot faster than GCC.
tcc is 8x faster, twice as fast isn't doing it justice.
As for the header thing, that'd could potentially be true if the compile time was something like 450ms -> 220ms, but why bother saying it when you're only saving a few hundred milliseconds
Going from 220 to 450 ms would be a disaster in my project. It has many thousands of files. Recompilation of almost everything happens from time to time.
If those made-up numbers were true, they would be very significant and an argument in favor of keeping the code in C
A 200ms difference is adding or removing 200lines lines of implementation, and spliting it up into a file can make it slower because of include overhead. You completely made up C being twice as fast as C++.
Surprisingly, this is not true. I've written a C++ file only to realize at the end that I did not use any C++ features. Renaming the file to .c halved the compilation time.