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build process.md

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Build Process

  • Build process represented as a Directed Graph.

    • Takes xcodeproj as the build description.

  • Each task has a signature and changes only when modified.

  • Framework gets embedded in app binary, which needs to be built for each platform.

  • XCFramework binary distribution.

  • Keep interface simple and least extensible, easy to add, hard to remove.

  • Can make functions and variables inlinable for performance. But once done can't change it. Also @frozen enums.

  • Header maps are used to communicate info from the build system to the clang compiler.

  • Clang modules to speed up the build.

  • Compilers run different sorts of optimization to

  • Can write defaults

    • defaults write com.apple.dt.Xcode ShowBuildOperationDuration -bool YES

  • Bitcode is llvm IR. We upload it to the app store which runs llvm-backend itself and it generates built for all available platforms. Fat Binary is removed. Any llvm optimization fix can run itself.

  • pod plugins list

  • There are two types of linking: static, and dynamic.

    • A dynamic framework is a dynamic library embedded in a bundle.
    • Umbrella Header

  • Can fake bitcode in debug app.

  • marker only mode is used to speed up the compilation while still producing enough information in the final output to check if all the files contain a bitcode section. -fembed-bitcode option will split the compilation into two stages and add measurable costs to compile time due to the extra process launch, the serialization and the verifier. -fembed-bitcode-marker is just a way to avoid that costs but still mark the section for the sanity check later (done by the linker in our case).

-fembed-bitcode option which breaks down the compilation into two stages. The first stage emits optimized bitcode and the second stage compiles bitcode into object file.

-fembed-bitcode-marker option which doesn't break down into two stages to speed up the compilation flow.

  • debug info

    • Mapping source to binary in debuggers, profilers, editors
    • Can be used for code auto-completion
    • Dwarf
      • Standard for debugging information
      • Interchange format generated by gcc, clang, icc, consumed by gdb, lldb, profilers

  • Auto delete the unused import

xcodebuild -workspace internalize.xcworkspace -scheme MY_SCHEME -configuration Debug > xcodebuild.log
swiftlet analyze --fix --compiler-log-path xcodebuild.log

References

  • Build System Xcode
  • Binary Framework Talk
  • Dynamic Library
  • dyld
    • Static library can save time loading dynamic libs
    • When used with an extension can create duplicate
    • Own library can be static
    • Debug build runs libMainThreadChecker which gives called from diff thread warning
    • dyld
      • load all dependent lib
      • rebase all dylib image
        • read entire data pages
        • copy on write
      • bind all dylib image
        • detect symbols, load all dependant libs, resolve
        • Position Independent code, data keeps address, text segment keeps stub, abstraction
      • prepare objc runtime
      • run initializer
  • Xcode Documentation