[CMake] Building third party libraries along with normal targets

[Robert Dailey]

On Wed, Mar 29, 2017 at 8:18 PM, Florent Castelli
<florent.castelli at gmail.com> wrote:
> This is known as "super build".
> Yes, this is exactly why I made my Boost CMake build scripts, which you use
> unless you changed your mind today :)

You mean this?
https://github.com/Orphis/boost-cmake

It's on the drawing board, for sure. It's the best solution I've
found. It's also part of the reason I'm asking this question to begin
with.

Although, this specific method of building boost doesn't use
superbuild, it uses normal add_subdirectory() with target.

> It can be done for other projects as well. Sometimes, they even provide
> CMake build scripts you can use directly with "add_subdirectory()" so you
> don't have to write CMake scripts or use "ExternalProject_Add()" (which
> isn't all great since it doesn't propagate all your current project
> settings).

Long term, I'm thinking a project like hunter[1] would be the best
choice. The problem with hunter is that it doesn't separate concerns
between host machine and target host. Specifically, when cross
compiling.

All the superbuild commands assume linux command syntax, simply
because I specified a toolchain utilizing android NDK. For this reason
it requires a lot of TLC to get working.

[1]: https://github.com/ruslo/hunter

> You can use ccache or its Windows variants to make it faster. But you also
> shouldn't need "ninja clean" most of the time. Possibly, you could just
> clean a specific target "ninja -t clean foo".
> If you declare all your dependencies properly, then you could just always
> run "ninja" and the build will just be correct.
> If your purpose is to see the compiler output again (to fix warnings), it is
> acceptable to clean and rebuild (with ccache it should be fast enough).
> Personally, I just have a very long history in my terminal and scroll back
> or pipe the build content to a file to look at it later. Some IDEs will also
> record all the compilation output and make it available later (Xcode does
> it), then it's less of an issue.

Never used ccache before, what does it do? Also if even if you ninja
-t to clean, it will also clean dependencies. So if I specify those
in-project dependencies that actually build third party libs, those
will be cleaned too.