Well, I tried upstreaming the new build scripts to some projects and it didn’t go well. Some of the reasons I’ve heard of: - Windows developpers don’t use CMake, they have project files on the repository. The CMake files for Windows will never be updated. - I installed CMake 2.8.6 five years ago and I don’t want to update yet again! People relying on old versions is quite common and any attempt to raise the min version will be frowned upon (see the discussion in the LLVM mailing lists for example). - We prefer to use autotools and don’t want to have to learn CMake. That’s fair. But also, no one likes to build an autotools backed project for Android or iOS.
Rewriting build scripts for all libraries isn’t trivial. But depending on the scale of your organization, it might make sense to spend the time. Google is doing something very similar by writing Blaze build scripts for the *world*. They can leverage all their infrastructure for fast and correct builds then. In a similar way here, we just have our compilation options set once in our toolchain file and that’s it, it works correctly, without duplicating jobs to build the libraries. Also, everything is built from the tip of the tree, which is a different software practice than using set releases. It’s not for everyone though. As for using a heterogenous build system, I’m really against it. Even if they work for the platform you are trying to target, you may run into other issues. Some build systems are really badly designed and will slowdown your iterations a lot. Most people here will use Ninja and have a very fast or instant “no-op” build. You may forget to keep options in sync. Or even might not be able to pass some options to the other build system. I’ve never heard of Spack before. It looks better than other solutions I’ve seen before. But you still have to manage all the options from your build script and publish the binaries somewhere. Then you need to teach your build scripts to get the right version. I won’t trade my builds from source for a set of prebuilt binaries anytime soon I think :) /Florent > On 16 Aug 2016, at 14:52, Elizabeth A. Fischer > <elizabeth.fisc...@columbia.edu> wrote: > > CMake builds for existing libraries are certainly an interesting and useful > thing, and deserve to be posted in a GitHub repo somewhere. They should also > serve as the basis of a campaign to get the library authors to incorporate > the CMake build directly in their repos. > > But any approach that requires every build to be ported to CMake will be > difficult and labor-prone to scale. Writing a meta-build recipe is usually > much easier. > > Spack handles the combinatorial dependencies you mention in a sophisticated, > graceful way that most meta-builders do not. Its only problem is it does not > (yet) run on Windows. There's no fundamental reason why not; we just need > someone to get involved and start trying it on Windows. > > -- Elizabeth > > > On Tue, Aug 16, 2016 at 6:52 AM, Florent Castelli <florent.caste...@gmail.com > <mailto:florent.caste...@gmail.com>> wrote: > At Spotify, we use CMake a lot for our large C++ library shared by all the > clients. > After trying to build libraries for each platform and variant, we basically > gave up and we now > use a super-build approach. > > For example, Boost is used by 5 platforms: Windows, OSX, Linux, Android and > iOS. > Each platform has a different CPU target (or many 32/64bit, x86/ARM). > Each platform has many compilers. > Some platforms have instrumentation options (Debug / Release, ASan, MSan…) > and really need > to be compiled properly, otherwise you’ll end up with false positives. > The matrix of builds is REALLY hard to track. Each time we update Boost, we > had to update > a lot of things. > I tried using ExternalProject and use b2 (build tool from Boost) to build it > and instead of having > lots of build jobs with a mirror of the flags, you end up mirroring the flags > in your CMake files > instead, which is still not good enough. > > In the end, I looked at how Boost is actually built. And for most libraries, > it’s plain simple. > A static library with a few files, some define, sometimes a platform specific > source file. > What if instead of having an external build tool, I built it from CMake > instead? > It would propagate all the build flags, target, instrumentation and compiler > information from the main > build to it and just work. > I tried it and it worked in no time! We replaced our Boost 1.59 binary > distribution with the source > distribution and it’s much easier. When people build our library for a > different target, they don’t have > to download new binaries, they just reuse the same sources. > Later on, we found a bug in Boost 1.59 (fixed in later versions) and patched > it. We updated our source > bundle and everything was smooth. > Much later on, we wanted to use 1.61. We just updated the source bundle > again, the list of source > files or compilation flags for the libraries we use didn’t change. It was > again effortless. > > Overall, building boost takes 10s on our developers’ machines. The sources > aren’t changed often, > so the cost is pretty low. It needs attention when we upgrade it, but that’s > quite rare. > > We try now to use the same approach for other libraries when we add them. > Some of them are > already using CMake and it’s somewhat easier, but since most people still > target version 2.8 (or 2.6...), > we find it better to rewrite the build scripts ourselves and use modern > features (as in, everything is > a target that propagates requirements, we don’t propagate variables). > It makes it also much easier to build a library for another platform that > wasn’t targeted by the original > project. > > If people are interested, I could share the CMakeLists.txt file we use for > Boost. It doesn’t build all > the libraries (some are hard like Context) and uses some internal macros, but > it should be plain > simple to tweak for your use. > > /Florent > > > On 12 Aug 2016, at 21:59, Robert Dailey <rcdailey.li...@gmail.com > > <mailto:rcdailey.li...@gmail.com>> wrote: > > > > Hello, > > > > There is an internal C++ product at the company I work for which I > > have written a series of CMake scripts for. This project actually has > > dependencies on several open source libraries, such as boost, > > freetype, openssl, etc. > > > > Right now what we do is build each of these third party libraries *by > > hand*, once for every platform we support (Windows, Linux x86, Android > > NDK). Then we stuff the includes (headers) and libraries > > (static/shared) in a submodule and the primary code base's CMake > > scripts pull them in as interface targets. > > > > This works well and is light-weight but is a pain when upgrading or > > changing libraries. It's a pain because if I want to upgrade boost, I > > have to build it up to 6 times (once for each platform and once for > > each configuration). > > > > I've been thinking of a different approach for a while. I've done some > > toying around with the "Super Build" concept, where I have a separate > > CMake project that does nothing but use the ExternalProject module to > > build libraries in real time along with our project. So the order of > > operations would be as follows (for our automated build server): > > > > 1. Clone our "Third Party" repository > > 2. Use CMake to generate & build the "Super Build" project (this > > builds boost, openssl, freetype, etc for the current platform). > > 3. Clone the main code base's repository > > 4. Use CMake to generate & build, using find_package() to refer to > > interface targets exported by those third party libraries built in > > step 2 > > > > Obviously this will make builds take significantly longer, because > > we're constantly rebuilding the same third party libraries over and > > over again. However, it virtually eliminates the maintenance burden > > for third party libraries because they are built inherently with > > everything else. > > > > Note that I can't refer to pre-built libraries in our build > > environments because we need very specific control over the versions > > of our libraries as well as the toolchains that were used to build > > them. Also we may specifically build our libraries a certain way (such > > as boost). For this reason we do not rely on our external environment > > or external package managers to fulfill third party dependencies, like > > most open source projects do on Linux for example. > > > > Does this "Super Build" approach sound like a better idea? What other > > options are available? The downside with the "Super Build" solution is > > that it will become very difficult to make the transition between > > building third party and building our code base seamless. I can't do > > both in the same generate step because find_package() can't be called > > until the libraries are built & installed. > > -- > > > > Powered by www.kitware.com <http://www.kitware.com/> > > > > Please keep messages on-topic and check the CMake FAQ at: > > http://www.cmake.org/Wiki/CMake_FAQ <http://www.cmake.org/Wiki/CMake_FAQ> > > > > Kitware offers various services to support the CMake community. For more > > information on each offering, please visit: > > > > CMake Support: http://cmake.org/cmake/help/support.html > > <http://cmake.org/cmake/help/support.html> > > CMake Consulting: http://cmake.org/cmake/help/consulting.html > > <http://cmake.org/cmake/help/consulting.html> > > CMake Training Courses: http://cmake.org/cmake/help/training.html > > <http://cmake.org/cmake/help/training.html> > > > > Visit other Kitware open-source projects at > > http://www.kitware.com/opensource/opensource.html > > <http://www.kitware.com/opensource/opensource.html> > > > > Follow this link to subscribe/unsubscribe: > > http://public.kitware.com/mailman/listinfo/cmake-developers > > <http://public.kitware.com/mailman/listinfo/cmake-developers> > > -- > > Powered by www.kitware.com <http://www.kitware.com/> > > Please keep messages on-topic and check the CMake FAQ at: > http://www.cmake.org/Wiki/CMake_FAQ <http://www.cmake.org/Wiki/CMake_FAQ> > > Kitware offers various services to support the CMake community. For more > information on each offering, please visit: > > CMake Support: http://cmake.org/cmake/help/support.html > <http://cmake.org/cmake/help/support.html> > CMake Consulting: http://cmake.org/cmake/help/consulting.html > <http://cmake.org/cmake/help/consulting.html> > CMake Training Courses: http://cmake.org/cmake/help/training.html > <http://cmake.org/cmake/help/training.html> > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > <http://www.kitware.com/opensource/opensource.html> > > Follow this link to subscribe/unsubscribe: > http://public.kitware.com/mailman/listinfo/cmake-developers > <http://public.kitware.com/mailman/listinfo/cmake-developers>
-- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/mailman/listinfo/cmake-developers
