We need to seriously think about what to do with C++ modules

Jussi Pakkanen, creator of the Meson build system, has some words about modules in C++.

If C++ modules can not show a 5× compilation time speedup (preferably 10×) on multiple existing open source code base, modules should be killed and taken out of the standard. Without this speedup pouring any more resources into modules is just feeding the sunk cost fallacy.

That seems like a harsh thing to say for such a massive undertaking that promises to make things so much better. It is not something that you can just belt out and then mic drop yourself out. So let’s examine the whole thing in unnecessarily deep detail. You might want to grab a cup of $beverage before continuing, this is going to take a while.
↫ Jussi Pakkanen

I’m not a programmer so I’m leaving this for the smarter people among us to debate.