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Comment by inetknght | Hacker News Reader

You should probably hire better C++ developers if it takes that long.

Maybe you shouldn't prejudge the quality of developers on a project you know nothing about

you should probably become more experienced in c/c++ development before sharing your opinion

You should see how quick C++ compilation times can be a competent organization like Google before dismissing that opinion.

Are you talking about clean builds or incremental builds?

They usually do incremental builds. And a lot of work goes into reproducible builds so that incremental builds can be trusted. But even clean builds are typically minutes of wall-clock time. Not hours.

Of course part of the trick is that work has been distributed across a cluster, so a lot longer was spent compiling than that...

How long should a giant C++ code base take to compile?

With a good CMake configuration and Ninja and ccache, a minute or two max.

Your CMake makes incremental builds safe, and the ccache saves you when switching between branches.

CMake helps a good bit, ccache goes further, and ninja helps a bit too. But none of them can help templated header-only libraries with complex interdependencies. It gets particularly bad when the developer #includes a convenience header to bring in _everything_ in the library instead of just what they need.

Agreed. Good use of PImpl when you have large external header-only libraries is also generally recommended to keep the dependency graph nicer.

Also from what I've seen, large header-only codebases tend to be external and thus generally don't change that much, so if you can limit your own internal dependency tree ccache can still save you.

How giant is giant?

I've seen tens of thousands of lines of code compile in 30 minutes.

I've seen a hundred thousand lines of code compile in 2 minutes.

It really depends on how the project is laid out. If you're using lots of header-only libraries and try to compile monolithically (like soooooo many C++ applications do these days), you're going to have a bad (compile) time.

tens of thousands? that's small. we're talking MLOCs here.

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