[noobermin]

brundolf is asking a similar yet different question, so I'll ask mine: I've heard about modules coming to C++. What are the concerns with headers exactly? I'm aware of the issues with duplication in object files and ballooning build times, but are there other issues? Is it then something that primarily affect very large code bases?

[ratww]

I think different people will have different answers. The biggest complaint is that this slows down builds, of course, but it also requires hacks to avoid re-including the same header twice when you have complex header hierarchies [1][2], bleed-trough of macros and pragmas, and of course you have to write forward declarations for everything you intend to publicly expose, as opposed to using a "public" keyword.

Honestly I dislike them because they're a redundant pain in the ass. I tried other solutions before (at one job I had 15 years ago we had automatic header code generation, ooof), and although modules are not that ready for primetime [3] (dependency resolution need to be done by an external program), I think they'll be the bees knees.

[1] https://en.wikipedia.org/wiki/Include_guard

[2] (some people will be quick to note that can be solved by pragmas)

[3] https://vector-of-bool.github.io/2019/01/27/modules-doa.html (but he wrote a follow up: https://vector-of-bool.github.io/2019/03/04/modules-doa-2.ht... )

[Gibbon1]

Not a C++ monkey but headers in C/C++ have the problem that you can't parse them independently of the source file they are included in because of the predecessor. Which means you need to re-parse them each and every time they are included in a project.

[celticmusic]

I think you meant preprocessor, not predecessor, lol. I had to reread that a time or two. I knew what you were trying to say and I still got confused by it.

[Gibbon1]

d'oh!

[shakna]

However, every modern C compiler and tools like cmake allow you to use precompiled headers to avoid that step if it is what you want to do.