Saturday, 10 February 2018

One MapGuide/FDO build system to rule them all?

Before the bombshell of the death of Autodesk Infrastructure Map Server was dropped, I was putting the final finishing touches of making (pun intended) the MapGuide/FDO build experience on Linux a more pleasant experience.

Namely, I had it with autotools (some may describe it as autohell) as the way to build MapGuide/FDO on Linux. For FDO, this was the original motivation for introducing CMake as an alternative. CMake is a more pleasant way to build software on Linux over autotools because:
  1. CMake builds your sources outside of the source tree. If you're doing development on a SVN working copy this is an absolute boon as it means when it comes time to commit any changes, you don't have to deal with sifting through tons of autotools-generated junk that is left in your actual SVN wc.
  2. CMake builds are faster than their autotools counterpart.
  3. It is much easier to find and consume external libraries with CMake than it is through autotools, which makes build times faster because we can just source system-installed copies of thirdparty libraries we use, instead of waste time having to build these copies (in our internal thirdparty source tree) ourselves. If we are able to use system-installed copies of libraries when building FDO, then we can take advantage of SVN sparse checkouts and be able to skip downloading whole chunks of thirdparty library sources that we never have to build!
Sadly, while this sounds nice in theory, the CMake way to build FDO had fallen into a state of disrepair. My distaste for autotools was sufficient motivation to get the CMake build back into working condition. Several weeks of bashing at various CMakeLists.txt files later, the FDO CMake build was operational again and had some several major advantages over the autotools build (in addition to what was already mentioned):
  • We can setup the CMake to generate build configurations for Ninja instead of standard make. A ninja-powered CMake build is faster than standard make ^.
  • On Ubuntu 14.04 LTS (the current Ubuntu version we're targeting), all the thirdparty libraries we use were available for us to apt-get install in the right version ranges, and the CMake build can take advantage of all of them. Not a single internal thirdparty library copy needs to be built!
  • We can easily light up compiler features like AddressSanitizer and linking with the faster gold instead of ld. AddressSanitizer in particular easily helped us catch some issues that have flew under the radar.
  • All of the unit tests are build-able and more importantly ... executable outside the source tree, making it easier to fix up whatever was failing.
Although we now had a functional FDO CMake build. MapGuide still was built on Linux using autotools. So for the same reasons and motivations, I started the process of introducing CMake to the MapGuide build system for Linux.

Unlike FDO, MapGuide still needed some of the internal thirdparty libraries built.
  • DBXML - No ubuntu package available, though we can get it to build against a system-provided version of xerces, so we can at least skip building that part of DBXML.
  • Apache HTTPD - Ubuntu package available, but having MapGuide be able to integrate with an Ubuntu-provided httpd installation was not in the scope of this work, even though this is a nice thing to have.
  • PHP - Same reasons as Apache HTTPD
  • Antigrain Geometry - No ubuntu package available. Also the AGG sources are basically wedded to our Renderers project anyways.
  • DWF Toolkit - No ubuntu package available
  • CS-Map - No ubuntu package available
For everything else, Ubuntu provided the package in the right version ranges for CMake to take advantage of. Another few weeks of bashing various CMakeLists.txt files into shape and we had FDO and MapGuide both build-able on Linux via CMake. To solve the problem of still needing to build some internal thirdparty libs, but still be able to retain the CMake quality of everything is built outside the source tree, some wrapper shell scripts are provided that will copy applicable thirdparty library sources out of the current directory, build them in their copied directories and then invoke CMake and pass in all the required parameters so that it will know where to look for the internal libraries to link against when it comes to build MapGuide proper.

This was also backported to FDO, so that on distros where we do not have all our required thirdparty libraries available, we can selectively build internal copies and be able to find/link the rest, and have CMake take care of all of that for us.

So what's with the title of this post?

Remember when I wrote about how interesting vcpkg was?

What is best used with vcpkg to easily consume thirdparty libraries on Windows? Why CMake of course! Now building MapGuide on Windows via CMake is not on the immediate horizon. We'll still be maintaining Visual Studio project files by hand (instead of auto-generating them with CMake) for the immediate future, but can you imagine being able to build FDO and MapGuide on both Windows and Linux with CMake and not have to waste time on huge SVN checkouts and building thirdparty libraries? That future is starting to look real possible now!

For the next major release of MapGuide Open Source, it is my plan to use CMake over autotools as the way to build both MapGuide and FDO on Linux.

^ Well, the ninja-powered CMake build used to be blazing fast until Meltdown and Spectre happened. My dev environment got the OS security patches and whatever build performance gains that were made through ninja and CMake were instantly wiped out and we were back to square one in terms of build time. Still, the autotools build performed worse after the meltdown patches, so while CMake still beats the autotools build in terms of build time, we ultimately gained nothing on this front.

Thanks Intel!!!