CMake General Discussion

• Intro
  • Windows has officially moved over to CMake
  • 1 Port to go (Mac), may never officially but can for engineers

• How many have built things on the mac with CMake?
  • 2 hands (1 just JSC, 1 JSC+WebCore)
  • Issue with WebKit is that it isn't testable yet

• JSC - FTL is disabled in CMake builds
  • other ports (GTK) have experience, feel likes it is close to turn on again
  • for Mac, there is already CMake code for linux to find LLVM builds, would need to customize for Mac

• Make Usable on Mac - Executables need to be generated correctly
  • NetworkProcess, WebProcess binaries / executables
  • Once they are put in the right place, they should be usable for engineers
  • Allow engineers to do things like run layout tests with CMake builds

• Build Speed Comparison
  • build-webkit --cmake to build-webkit not a fair comparison
    • no precompiled headers
    • different set of projects are built (minibrowser)
  • If you generate an Xcode project and build that it is compariable
    • 25-30% faster
    • potential for cross-compiling / distributed builds

• Distributed Builds
  • Igalia used icc, ships the toolchain across the network
  • How much of a speedup do we see?
    • Hard to say. Depends on your laptop.
  • How long is a clean build?
    • It spreads, so it depends on users.
  • Does it sync SDKs?
    • On linux ports, it ships the toolchain.
  • rniwa: Tried distcc at Google
    • Slower than if you had a Mac with 24 cores
  • on Mac, linking is a very long task
  • Igalia saw some benefits changing linkers
    • different linker strategy allowed them to use debug builds
    • thin archives does less work upfront

• Pros
  • faster incrementable builds
  • easier to move files around
  • easier to understand inputs/outputs
  • no DerivedSources.make duplicate info
    • can catch Makefile issues early in build time due to checking dependencies early
• Cons
  • possible incompatibilities with future unreleased builds of Xcode
    • very unlikely there will be an Xcode project incompatibility change
    • may be an invalid concern
  • limited to what CMake can do correctly

Feature Flag Discussion

• Toggling feature flags happen in many places
  • FeatureDefines.h
  • webkitpl build flags
  • Xcode Configuration files
  • Source/CMake/WebKitFeatures.cmake (and platform impls)

• Cleanup
  • if everyone uses CMake yes, hopefully we can reduce this to just the CMake ones

Questions

• What is the relationship between CMake and distributed builds?
  • cannot do distributed builds with Xcode.

• When for Mac?
  • when executables get in the right place, should be suitable for engineering builds
  • AppKit links WebKit, so we need to generate a WebKit.framework

• Is there good documentation for CMake commands?
  • documentation has improved
  • cmake --help --full
  • depends on the versions

• If we got it to the point engineers could use it for tests, would people use it?
  • Number of yesses.