[CMake] CMAKE_OSX_SYSROOT icw iOS fat binaries (iPhone + iPhoneSimulator)

[Craig Scott]

The IOS_INSTALL_COMBINED
<https://cmake.org/cmake/help/latest/prop_tgt/IOS_INSTALL_COMBINED.html> target
property allows you to create fat binaries, but only at install time. To
use this feature, set your CMAKE_OSX_SYSROOT to iphoneos and the simulator
slice will be built and added to the fat binary for you automatically
during the install step. If you require fat binaries at build time, that
could be much more challenging.


On Mon, Nov 19, 2018 at 10:19 PM Erik van Nooijen <
Eric.vanNooijen at tomtom.com> wrote:

>  With CMake it is possible to build for fat binaries for iOS without
> XCode. Fat binaries meaning containing all the architectures for iPhone and
> iPhoneSimulator.
>
> However, when building frameworks, CMake builds it with the MacOSX layout,
> including '*Version*' directory and symlinks etc. This is wrong when
> building for iOS.
>
> The reason is that CMake determines bundle layout based on
> CMAKE_OSX_SYSROOT, but this cannot be set correctly in this situation, as
> it allows only one directory to be set, and we'd need two (iPhone and
> iPhoneSimulator). In short:
>
> * not setting CMAKE_OSX_SYSROOT results in MacOSX framework/bundle layouts
>
> * setting CMAKE_OSX_SYSROOT to a single sysroot gives error for the other
> architecture(s)
>
>   ld: dynamic main executables must link with libSystem.dylib for
> architecture i386
>
> * setting CMAKE_OSX_SYSROOT to multiple sysroots gives error for incorrect
> paths
>
>   Ignoring CMAKE_OSX_SYSROOT value:
>
>
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS10.1.sdk;/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator10.1.sdk
>
>   because the directory does not exist.
>
>
>
> Please find below an example CMakeLists.txt to test/verify this. The
> behaviour can be switched on and off with the MAKE_FAT variable.
>
>
>
> What is the correct way to get fat binaries in the correct iOS layout in
> such a case?
>
>
>
> cmake_minimum_required(VERSION 3.13)
>
> project(iOSFatBinaries)
>
> set(MAKE_FAT TRUE)
>
>
>
> execute_process(COMMAND xcodebuild -version -sdk iphoneos        Path
> COMMAND perl -ne "chomp;print;exit;" OUTPUT_VARIABLE SDK_IPHONE_ROOT)
>
> execute_process(COMMAND xcodebuild -version -sdk iphonesimulator Path
> COMMAND perl -ne "chomp;print;exit;" OUTPUT_VARIABLE
> SDK_IPHONE_SIMULATOR_ROOT)
>
>
>
> # CMAKE_OSX_ARCHITECTURES
>
> if(MAKE_FAT)
>
>   set(CMAKE_OSX_ARCHITECTURES "armv7;armv7s;arm64;i386;x86_64" CACHE
> INTERNAL "Set supported OSX architectures")
>
> else()
>
>   set(CMAKE_OSX_ARCHITECTURES "armv7;armv7s;arm64" CACHE INTERNAL "Set
> supported OSX architectures")
>
> endif()
>
>
>
> # CMAKE_C_FLAGS and CMAKE_CXX_FLAGS
>
> if(MAKE_FAT)
>
>   set(SYSROOT_FLAGS "                 -arch armv7  -Xarch_armv7
> \"-isysroot${SDK_IPHONE_ROOT}\"")
>
>   set(SYSROOT_FLAGS "${SYSROOT_FLAGS} -arch armv7s -Xarch_armv7s
> \"-isysroot${SDK_IPHONE_ROOT}\"")
>
>   set(SYSROOT_FLAGS "${SYSROOT_FLAGS} -arch arm64  -Xarch_arm64
> \"-isysroot${SDK_IPHONE_ROOT}\"")
>
>   set(SYSROOT_FLAGS "${SYSROOT_FLAGS} -arch i386   -Xarch_i386
> \"-isysroot${SDK_IPHONE_SIMULATOR_ROOT}\"")
>
>   set(SYSROOT_FLAGS "${SYSROOT_FLAGS} -arch x86_64 -Xarch_x86_64
> \"-isysroot${SDK_IPHONE_SIMULATOR_ROOT}\"")
>
>   set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS}   ${SYSROOT_FLAGS}" CACHE INTERNAL
> "CMake C Compiler Flags")
>
>   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${SYSROOT_FLAGS}" CACHE INTERNAL
> "CMake CXX Compiler Flags")
>
> else()
>
>   SET(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS}   -arch armv7 -arch armv7s -arch
> arm64")
>
>   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -arch armv7 -arch armv7s -arch
> arm64")
>
> endif()
>
>
>
> # CMAKE_CXX_FLAGS
>
> if(MAKE_FAT)
>
>   set(CMAKE_OSX_SYSROOT "" CACHE INTERNAL "sysroot" FORCE)
>
> else()
>
>   set(CMAKE_OSX_SYSROOT ${SDK_IPHONE_ROOT} CACHE INTERNAL "sysroot" FORCE)
>
> endif()
>
>
>
> add_library(${PROJECT_NAME} SHARED
>
>   lib.h
>
>   lib.cpp
>
> )
>
>
>
> # Framework properties
>
> set_target_properties(${PROJECT_NAME} PROPERTIES
>
>   FRAMEWORK TRUE
>
>   FORCE_IOS_BUNDLE_LAYOUT TRUE
>
>   MACOSX_FRAMEWORK_IDENTIFIER ${PROJECT_NAME}
>
>   MACOSX_FRAMEWORK_BUNDLE_VERSION 1.0
>
>   MACOSX_FRAMEWORK_SHORT_VERSION_STRING 1.0
>
>   MACOSX_FRAMEWORK_INFO_PLIST ${CMAKE_CURRENT_SOURCE_DIR}/Info.plist.in
>
>   PUBLIC_HEADER lib.h
>
> )
>
>

-- 
Craig Scott
Melbourne, Australia
https://crascit.com

New book released: Professional CMake: A Practical Guide
<https://crascit.com/professional-cmake/>
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