[PATCH] D13605: [CMake] [Darwin] Add support for generating Xcode-compatible toolchains that xcodebuild and xcrun can search

[Justin Bogner via llvm-commits]

Chris Bieneman via llvm-commits <llvm-commits at lists.llvm.org> writes:
> beanz created this revision.
> beanz added a reviewer: Bigcheese.
> beanz added a subscriber: llvm-commits.
>
> Sometimes you want to install a custom compiler and use it like the
> system compiler without overriding the system compiler. This patch
> lets you create xctoolchains that the darwin command line tools can
> use.

This is really useful. A couple of comments below, but this basically
LGTM.

> To use this patch set LLVM_CREATE_XCODE_TOOLCHAIN=On in your CMake
> invocation and build the `install-code-toolchain` target.
>
> After installation you can set the envar EXTERNAL_TOOLCHAINS_DIR to
> your installed Toolchains directory, and the TOOLCHAINS envar to the
> toolchain identifier (ex org.llvm.3.8.0svn). This will then cause
> /usr/bin/clang to call your newly installed clang.
>
> http://reviews.llvm.org/D13605
>
> Files:
>   tools/xcode-toolchain/CMakeLists.txt
>
> Index: tools/xcode-toolchain/CMakeLists.txt
> ===================================================================
> --- /dev/null
> +++ tools/xcode-toolchain/CMakeLists.txt
> @@ -0,0 +1,62 @@
> +# OS X 10.11 El Capitan has just been released. One of the new features, System
> +# Integrity Protection, prevents modifying the base OS install, even with sudo.
> +# This prevents LLVM developers on OS X from being able to easily install new
> +# system compilers. The feature can be disabled, but to make it easier for
> +# developers to work without disabling SIP, this file can generate an Xcode
> +# toolchain. Xcode toolchains are a mostly-undocumented feature that allows
> +# multiple copies of low level tools to be installed to different locations, and
> +# users can easily switch between them.
> +
> +# Setting an environment variable TOOLCHAINS to the toolchain's identifier will
> +# result in /usr/bin/<tool> or xcrun <tool> to find the tool in the toolchain.
> +
> +# To make this work with Xcode 7.1 and later you can install the toolchain this
> +# file generates anywhere on your system and set EXTERNAL_TOOLCHAINS_DIR to the
> +# path specified by $CMAKE_INSTALL_PREFIX/Toolchains
> +
> +# This file generates a custom install-xcode-toolchain target which constructs
> +# and installs a toolchain with the identifier in the pattern:
> +# org.llvm.${PACKAGE_VERSION}. This toolchain can then be used to override the
> +# system compiler by setting TOOLCHAINS=org.llvm.${PACKAGE_VERSION} in the
> +# in the environment.
> +
> +if(NOT APPLE)
> +  return()
> +endif()
> +
> +option(LLVM_CREATE_XCODE_TOOLCHAIN "Create a target to install LLVM into an Xcode toolchain" Off)
> +
> +if(NOT LLVM_CREATE_XCODE_TOOLCHAIN)
> +  return()
> +endif()
> +
> +execute_process(
> +  COMMAND xcodebuild -find clang

I'd probably use `xcrun -find` rather than `xcodebuild -find`. Not that
it makes much of a difference.

> +  OUTPUT_VARIABLE clang_path
> +  OUTPUT_STRIP_TRAILING_WHITESPACE
> +  ERROR_FILE /dev/null
> +)
> +string(REGEX MATCH "(.*Toolchains).*" toolchains_match ${clang_path})

Seems slightly safer/clearer to match "(.*/Toolchains)/.*"

> +if(NOT toolchains_match)
> +  message(FATAL_ERROR "Could not identify toolchain dir")
> +endif()
> +set(toolchains_dir ${CMAKE_MATCH_1})
> +
> +set(XcodeDefaultInfo "${toolchains_dir}/XcodeDefault.xctoolchain/ToolchainInfo.plist")

What happens if you've already installed the custom toolchain? I guess
$toolchains_dir will point to $EXTERNAL_TOOLCHAINS_DIR and this will
fail.

> +set(LLVMToolchainDir "${CMAKE_INSTALL_PREFIX}/Toolchains/LLVM${PACKAGE_VERSION}.xctoolchain/")
> +
> +add_custom_command(OUTPUT ${LLVMToolchainDir}
> +                    COMMAND ${CMAKE_COMMAND} -E make_directory ${LLVMToolchainDir})
> +
> +add_custom_command(OUTPUT ${LLVMToolchainDir}/ToolchainInfo.plist
> +                  DEPENDS ${LLVMToolchainDir}
> +                  COMMAND ${CMAKE_COMMAND} -E copy "${XcodeDefaultInfo}" "${LLVMToolchainDir}/ToolchainInfo.plist"
> +                  COMMAND /usr/libexec/PlistBuddy -c "Set:Identifier org.llvm.${PACKAGE_VERSION}" "${LLVMToolchainDir}/ToolchainInfo.plist")
> +
> +add_custom_target(install-xcode-toolchain
> +                  DEPENDS ${LLVMToolchainDir}/ToolchainInfo.plist
> +                  COMMAND "${CMAKE_COMMAND}" --build ${CMAKE_BINARY_DIR} --target all
> +                  COMMAND "${CMAKE_COMMAND}"
> +                          -DCMAKE_INSTALL_PREFIX=${LLVMToolchainDir}/usr/
> +                          -P "${CMAKE_BINARY_DIR}/cmake_install.cmake"
> +                  ${cmake_3_2_USES_TERMINAL})