CMake/Modules/Platform/Darwin-Initialize.cmake

# Ask xcode-select where to find /Developer or fall back to ancient location.
execute_process(COMMAND xcode-select -print-path
  OUTPUT_VARIABLE _stdout
  OUTPUT_STRIP_TRAILING_WHITESPACE
  ERROR_VARIABLE _stderr
  RESULT_VARIABLE _failed)
if(NOT _failed AND IS_DIRECTORY ${_stdout})
  set(OSX_DEVELOPER_ROOT ${_stdout})
elseif(IS_DIRECTORY "/Developer")
  set(OSX_DEVELOPER_ROOT "/Developer")
else()
  set(OSX_DEVELOPER_ROOT "")
endif()

execute_process(COMMAND sw_vers -productVersion
  OUTPUT_VARIABLE CURRENT_OSX_VERSION
  OUTPUT_STRIP_TRAILING_WHITESPACE)

# Save CMAKE_OSX_ARCHITECTURES from the environment.
set(CMAKE_OSX_ARCHITECTURES "$ENV{CMAKE_OSX_ARCHITECTURES}" CACHE STRING
  "Build architectures for OSX")

# macOS, iOS, tvOS, and watchOS should lookup compilers from
# Platform/Apple-${CMAKE_CXX_COMPILER_ID}-<LANG>
set(CMAKE_EFFECTIVE_SYSTEM_NAME "Apple")

#----------------------------------------------------------------------------
# _CURRENT_OSX_VERSION - as a two-component string: 10.5, 10.6, ...
#
string(REGEX REPLACE "^([0-9]+\\.[0-9]+).*$" "\\1"
  _CURRENT_OSX_VERSION "${CURRENT_OSX_VERSION}")

#----------------------------------------------------------------------------
# CMAKE_OSX_DEPLOYMENT_TARGET

# Set cache variable - end user may change this during ccmake or cmake-gui configure.
if(CMAKE_SYSTEM_NAME STREQUAL "Darwin" AND _CURRENT_OSX_VERSION VERSION_GREATER 10.3)
  set(CMAKE_OSX_DEPLOYMENT_TARGET "$ENV{MACOSX_DEPLOYMENT_TARGET}" CACHE STRING
    "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value.")
endif()

#----------------------------------------------------------------------------
# CMAKE_OSX_SYSROOT

if(CMAKE_OSX_SYSROOT)
  # Use the existing value without further computation to choose a default.
  set(_CMAKE_OSX_SYSROOT_DEFAULT "${CMAKE_OSX_SYSROOT}")
elseif(NOT "x$ENV{SDKROOT}" STREQUAL "x" AND
        (NOT "x$ENV{SDKROOT}" MATCHES "/" OR IS_DIRECTORY "$ENV{SDKROOT}"))
  # Use the value of SDKROOT from the environment.
  set(_CMAKE_OSX_SYSROOT_DEFAULT "$ENV{SDKROOT}")
elseif(CMAKE_SYSTEM_NAME STREQUAL iOS)
  set(_CMAKE_OSX_SYSROOT_DEFAULT "iphoneos")
elseif(CMAKE_SYSTEM_NAME STREQUAL tvOS)
  set(_CMAKE_OSX_SYSROOT_DEFAULT "appletvos")
elseif(CMAKE_SYSTEM_NAME STREQUAL watchOS)
  set(_CMAKE_OSX_SYSROOT_DEFAULT "watchos")
elseif("${CMAKE_GENERATOR}" MATCHES Xcode
       OR CMAKE_OSX_DEPLOYMENT_TARGET
       OR CMAKE_OSX_ARCHITECTURES MATCHES "[^;]"
       OR NOT EXISTS "/usr/include/sys/types.h")
  # Find installed SDKs in either Xcode-4.3+ or pre-4.3 SDKs directory.
  set(_CMAKE_OSX_SDKS_DIR "")
  if(OSX_DEVELOPER_ROOT)
    foreach(d Platforms/MacOSX.platform/Developer/SDKs SDKs)
      file(GLOB _CMAKE_OSX_SDKS ${OSX_DEVELOPER_ROOT}/${d}/*)
      if(_CMAKE_OSX_SDKS)
        set(_CMAKE_OSX_SDKS_DIR ${OSX_DEVELOPER_ROOT}/${d})
        break()
      endif()
    endforeach()
  endif()

  if(_CMAKE_OSX_SDKS_DIR)
    # Select SDK for current OSX version accounting for the known
    # specially named SDKs.
    set(_CMAKE_OSX_SDKS_VER_SUFFIX_10.4 "u")
    set(_CMAKE_OSX_SDKS_VER_SUFFIX_10.3 ".9")

    # find the latest SDK
    set(_CMAKE_OSX_LATEST_SDK_VERSION "0.0")
    file(GLOB _CMAKE_OSX_SDKS RELATIVE "${_CMAKE_OSX_SDKS_DIR}" "${_CMAKE_OSX_SDKS_DIR}/MacOSX*.sdk")
    foreach(_SDK ${_CMAKE_OSX_SDKS})
      if(_SDK MATCHES "MacOSX([0-9]+\\.[0-9]+)[^/]*\\.sdk" AND CMAKE_MATCH_1 VERSION_GREATER ${_CMAKE_OSX_LATEST_SDK_VERSION})
        set(_CMAKE_OSX_LATEST_SDK_VERSION "${CMAKE_MATCH_1}")
      endif()
    endforeach()

    # pick an SDK that works
    set(_CMAKE_OSX_SYSROOT_DEFAULT)
    foreach(ver ${CMAKE_OSX_DEPLOYMENT_TARGET}
                ${_CURRENT_OSX_VERSION}
                ${_CMAKE_OSX_LATEST_SDK_VERSION})
      set(_CMAKE_OSX_DEPLOYMENT_TARGET ${ver})
      set(_CMAKE_OSX_SDKS_VER ${_CMAKE_OSX_DEPLOYMENT_TARGET}${_CMAKE_OSX_SDKS_VER_SUFFIX_${_CMAKE_OSX_DEPLOYMENT_TARGET}})
      set(_CMAKE_OSX_SYSROOT_CHECK "${_CMAKE_OSX_SDKS_DIR}/MacOSX${_CMAKE_OSX_SDKS_VER}.sdk")
      if(IS_DIRECTORY "${_CMAKE_OSX_SYSROOT_CHECK}")
        set(_CMAKE_OSX_SYSROOT_DEFAULT "${_CMAKE_OSX_SYSROOT_CHECK}")
        break()
      endif()
    endforeach()

    if(NOT CMAKE_CROSSCOMPILING AND NOT CMAKE_OSX_DEPLOYMENT_TARGET AND _CURRENT_OSX_VERSION VERSION_LESS _CMAKE_OSX_DEPLOYMENT_TARGET)
      set(CMAKE_OSX_DEPLOYMENT_TARGET ${_CURRENT_OSX_VERSION} CACHE STRING
        "Minimum OS X version to target for deployment (at runtime); newer APIs weak linked. Set to empty string for default value." FORCE)
    endif()
  else()
    # Assume developer files are in root (such as Xcode 4.5 command-line tools).
    set(_CMAKE_OSX_SYSROOT_DEFAULT "")
  endif()
endif()

# Set cache variable - end user may change this during ccmake or cmake-gui configure.
# Choose the type based on the current value.
set(_CMAKE_OSX_SYSROOT_TYPE STRING)
foreach(v CMAKE_OSX_SYSROOT _CMAKE_OSX_SYSROOT_DEFAULT)
  if("x${${v}}" MATCHES "/")
    set(_CMAKE_OSX_SYSROOT_TYPE PATH)
    break()
  endif()
endforeach()
set(CMAKE_OSX_SYSROOT "${_CMAKE_OSX_SYSROOT_DEFAULT}" CACHE ${_CMAKE_OSX_SYSROOT_TYPE}
  "The product will be built against the headers and libraries located inside the indicated SDK.")

# Resolves the SDK name into a path
function(_apple_resolve_sdk_path sdk_name ret)
  execute_process(
    COMMAND xcrun -sdk ${sdk_name} --show-sdk-path
    OUTPUT_VARIABLE _stdout
    OUTPUT_STRIP_TRAILING_WHITESPACE
    ERROR_VARIABLE _stderr
    RESULT_VARIABLE _failed
  )
  set(${ret} "${_stdout}" PARENT_SCOPE)
endfunction()
# Handle multi-arch sysroots. Do this before CMAKE_OSX_SYSROOT is
# transformed into a path, so that we know the sysroot name.
function(_apple_resolve_multi_arch_sysroots)
  if(CMAKE_APPLE_ARCH_SYSROOTS)
    return() # Already cached
  endif()

  list(LENGTH CMAKE_OSX_ARCHITECTURES _num_archs)
  if(NOT (_num_archs GREATER 1))
    return() # Only apply to multi-arch
  endif()

  if(CMAKE_OSX_SYSROOT STREQUAL "macosx")
    # macOS doesn't have a simulator sdk / sysroot, so there is no need to handle per-sdk arches.
    return()
  endif()

  if(IS_DIRECTORY "${CMAKE_OSX_SYSROOT}")
    if(NOT CMAKE_OSX_SYSROOT STREQUAL _CMAKE_OSX_SYSROOT_DEFAULT)
      message(WARNING "Can not resolve multi-arch sysroots with CMAKE_OSX_SYSROOT set to path (${CMAKE_OSX_SYSROOT})")
    endif()
    return()
  endif()

  string(REPLACE "os" "simulator" _simulator_sdk ${CMAKE_OSX_SYSROOT})
  set(_sdks "${CMAKE_OSX_SYSROOT};${_simulator_sdk}")
  foreach(sdk ${_sdks})
    _apple_resolve_sdk_path(${sdk} _sdk_path)
    if(NOT IS_DIRECTORY "${_sdk_path}")
      message(WARNING "Failed to resolve SDK path for '${sdk}'")
      continue()
    endif()

    execute_process(
      COMMAND plutil -extract SupportedTargets.${sdk}.Archs json ${_sdk_path}/SDKSettings.plist -o -
      OUTPUT_VARIABLE _sdk_archs_json
      OUTPUT_STRIP_TRAILING_WHITESPACE
      ERROR_VARIABLE _stderr
      RESULT_VARIABLE _failed
      )
    if(_failed)
      # Failure to extract supported architectures for an SDK means that the installed SDK is old
      # and does not provide such information (SDKs that come with Xcode >= 10.x started providing
      # the information). In such a case, return early, and handle multi-arch builds the old way
      # (no per-sdk arches).
      return()
    endif()

    # Poor man's JSON decoding
    string(REGEX REPLACE "[]\\[\"]" "" _sdk_archs ${_sdk_archs_json})
    string(REPLACE "," ";" _sdk_archs ${_sdk_archs})

    set(_sdk_archs_${sdk} ${_sdk_archs})
    set(_sdk_path_${sdk} ${_sdk_path})
  endforeach()

  foreach(arch ${CMAKE_OSX_ARCHITECTURES})
    set(_arch_sysroot "")
    foreach(sdk ${_sdks})
      list(FIND _sdk_archs_${sdk} ${arch} arch_index)
      if(NOT arch_index EQUAL -1)
        set(_arch_sysroot ${_sdk_path_${sdk}})
        break()
      endif()
    endforeach()
    if(_arch_sysroot)
      list(APPEND _arch_sysroots ${_arch_sysroot})
    else()
      message(WARNING "No SDK found for architecture '${arch}'")
      list(APPEND _arch_sysroots "") # Placeholder
    endif()
  endforeach()

  set(CMAKE_APPLE_ARCH_SYSROOTS "${_arch_sysroots}" CACHE INTERNAL
    "Architecture dependent sysroots, one per CMAKE_OSX_ARCHITECTURES")
endfunction()

_apple_resolve_multi_arch_sysroots()

# Transform CMAKE_OSX_SYSROOT to absolute path
set(_CMAKE_OSX_SYSROOT_PATH "")
if(CMAKE_OSX_SYSROOT)
  if("x${CMAKE_OSX_SYSROOT}" MATCHES "/")
    # This is a path to the SDK.  Make sure it exists.
    if(NOT IS_DIRECTORY "${CMAKE_OSX_SYSROOT}")
      message(WARNING "Ignoring CMAKE_OSX_SYSROOT value:\n ${CMAKE_OSX_SYSROOT}\n"
        "because the directory does not exist.")
      set(CMAKE_OSX_SYSROOT "")
    endif()
    set(_CMAKE_OSX_SYSROOT_PATH "${CMAKE_OSX_SYSROOT}")
  else()
    _apple_resolve_sdk_path(${CMAKE_OSX_SYSROOT} _sdk_path)
    if(IS_DIRECTORY "${_sdk_path}")
      set(_CMAKE_OSX_SYSROOT_PATH "${_sdk_path}")
      # For non-Xcode generators use the path.
      if(NOT "${CMAKE_GENERATOR}" MATCHES "Xcode")
        set(CMAKE_OSX_SYSROOT "${_CMAKE_OSX_SYSROOT_PATH}")
      endif()
    endif()
  endif()
endif()