[CMake] Adding Mac OS X Style Frameworks On Linux

[Alexander Neundorf]

On Wednesday 31 March 2010, Karol Krizka wrote:
> Hi there,
>
> I am trying to use CMake to develop Apps for a jailbroken iPhone using
> the iphonedevonlinux toolchain[1]. I got the toolchain to work and
> build the included test app, HelloToolchain. What I am trying to do
> next is write a CMakeLists.txt for this test App. I renamed it as
> KKToolchain for CMake enabled testing. Anyways, if you want to see
> what the Makefile should look like, see here[2].
>
> The way I am trying to accomplish is to use CMake's Cross Compiling
> support[3]. As per the WiKi entry, I've created a toolchain file
> called Toolchain-iphone.cmake and filled it in with the following:
>
> SET(CMAKE_SYSTEM_NAME Darwin)
> SET(CMAKE_SYSTEM_VERSION 9)
> SET(CMAKE_SYSTEM_PROCESSOR arm-apple-darwin9)
> SET(IPHONE_TOOLCHAIN_DIR /home/kkrizka/Sources/iphonedevonlinux/toolchain)
> SET(CMAKE_C_COMPILER
> ${IPHONE_TOOLCHAIN_DIR}/pre/bin/${CMAKE_SYSTEM_PROCESSOR}-gcc)
> SET(CMAKE_CXX_COMPILER
> ${IPHONE_TOOLCHAIN_DIR}/pre/bin/${CMAKE_SYSTEM_PROCESSOR}-g++)
> SET(CMAKE_FIND_ROOT_PATH  ${IPHONE_TOOLCHAIN_DIR})
> SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
> SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
> SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
>
> As for the CMakeLists.txt file, I used the following:
>
> PROJECT(KKToolchain)
> SET(KKToolchain_SOURCES src/KKToolchain.m)
> SET(KKToolchain_LIBRARIES objc)
> ADD_EXECUTABLE(KKToolchain ${KKToolchain_SOURCES})
> TARGET_LINK_LIBRARIES(KKToolchain ${KKToolchain_LIBRARIES})
> SET(CMAKE_EXE_LINKER_FLAGS "-bind_at_load -framework Foundation
> -framework CoreFoundation -framework UIKit -w")
>
> After I compile the binary, I manually create a bundle and copy it to
> my iPhone using the commands from the HelloToolchain Makefile. I plan
> to find a way to automate this in CMake later. But right now, this
> works perfectly.
>
> Next, I would like to add a way to link against the different
> frameworks using a macro without having to modify
> CMAKE_EXE_LINKER_FLAGS.
> For example, I want to replace this:
> SET(CMAKE_EXE_LINKER_FLAGS "-bind_at_load -framework Foundation
> -framework CoreFoundation -framework UIKit -w")
> by this:
> TARGET_ADD_FRAMEWORKS(KKToolchain Foundation CoreFoundation UIKit)
>
> One suggestion I found way to use the TARGET_ADD_LIBRARIES macro[4] to
> add the frameworks. On Mac OS X this should work, but it does not work
> on Linux. My question is, is it possible to trick CMake thinking that
> it is working in an Mac OSX environment, so it would correctly add the
> frameworks at the linking stage?
>
> I tried a macro that I found on StackOverflow[5]. Basically, I've
> added the following at the end of my CMakeLists.txt
>
> SET(CMAKE_OSX_SYSROOT ${IPHONE_TOOLCHAIN_DIR}/sys)
> MACRO(ADD_FRAMEWORK fwname appname)
>   FIND_LIBRARY(FRAMEWORK_${fwname}
>     NAMES ${fwname}
>     PATHS ${CMAKE_OSX_SYSROOT}/System/Library
>     PATH_SUFFIXES Frameworks
>     NO_DEFAULT_PATH)
>   IF( ${FRAMEWORK_${fwname}} STREQUAL FRAMEWORK_${fwname}-NOTFOUND)
>     MESSAGE(ERROR ": Framework ${fwname} not found")
>   ELSE()
>     TARGET_LINK_LIBRARIES(${appname} ${FRAMEWORK_${fwname}})
>     MESSAGE(STATUS "Framework ${fwname} found at ${FRAMEWORK_${fwname}}")
>   ENDIF()
> ENDMACRO(ADD_FRAMEWORK)
> ADD_FRAMEWORK(Foundation KKToolchain)
>
> The output is as follows:
>
> kkrizka at sein:~/Sources/iphonedevonlinux/apps/KKToolchain/build$ cmake
> -DCMAKE_TOOLCHAIN_FILE=../Toolchain-iphone.cmake ..
> -- The C compiler identification is GNU
> -- The CXX compiler identification is GNU
> -- Check for working C compiler:
> /home/kkrizka/Sources/iphonedevonlinux/toolchain/pre/bin/arm-apple-darwin9-
>gcc -- Check for working C compiler:
> /home/kkrizka/Sources/iphonedevonlinux/toolchain/pre/bin/arm-apple-darwin9-
>gcc -- works
> -- Detecting C compiler ABI info
> -- Detecting C compiler ABI info - done
> -- Check for working CXX compiler:
> /home/kkrizka/Sources/iphonedevonlinux/toolchain/pre/bin/arm-apple-darwin9-
>g++ -- Check for working CXX compiler:
> /home/kkrizka/Sources/iphonedevonlinux/toolchain/pre/bin/arm-apple-darwin9-
>g++ -- works
> -- Detecting CXX compiler ABI info
> -- Detecting CXX compiler ABI info - done
> -- Framework Foundation found at
> /home/kkrizka/Sources/iphonedevonlinux/toolchain/sys/System/Library/Framewo
>rks/Foundation.framework -- Configuring done
> WARNING: Target "KKToolchain" requests linking to directory
> "/home/kkrizka/Sources/iphonedevonlinux/toolchain/sys/System/Library/Framew
>orks/Foundation.framework". Targets may link only to libraries.  CMake is
> dropping the item.
> -- Generating done
> -- Build files have been written to:
> /home/kkrizka/Sources/iphonedevonlinux/apps/KKToolchain/build
>
> As you can see, it correctly finds the Foundation framework in my
> toolchain. But it complains when I try to link to it. I am assuming
> that this is because linking to frameworks in only supported on Mac OS
> X. Is this true? If so, is there some other way around it?

Please put this in the cmake bug tracker at http://public.kitware.com/Bug/

About the linking-to-frameworks... I remember there is something hardcoded 
somewhere which detects whether something is a framework and then does 
something... will have to look.
Maybe somewhere a change from an #ifdef to something like a if (systemname 
== "Darwin") might help...

Alex