I am using openadk on the raspberry pi 3, and have an appliance where I have one main application that is running all the time.

So I am using gcc 7.2.0 from openadk, and compilation starts to be *very slow* with gcc: 10 minutes for a full rebuild... So I am looking into having the clang toolchain available next to the gcc one so I can compile only my application with clang, which is faster.

I have several shared libraries I also compile myself as part of my application build, all using cmake.

So, I used the llvm package under the toolchain dir and modified it so it could build in another output directory like this:

Then as llvm triple I used this:

LLVM_TRIPLE:=arm-openadk-linux-uclibceabihf

And the version I used was 5.0.2 of llvm.

So that compiled for me and I got indeed a toolchain in the TOOLCHAIN_USERLAND_DIR location, which I added in vars.mk. So then I needed a toolchain-userland.cmake file to be able to use it, and this is what I came up with:

set(CMAKE_SYSTEM_NAME Linux)

set(CMAKE_SYSTEM_PROCESSOR arm)

set(MY_GCC_TOOLCHAIN /Volumes/CASE/my-os-pi3/toolchain_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf)

set(MY_CLANG_TOOLCHAIN /Volumes/CASE/my-os-pi3/toolchain_userland_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf)

SET(CROSS_MACHINE_FLAGS "-marm -mcpu=cortex-a53 -mfloat-abi=hard -mfpu=vfp")

set(MY_COMMON_COMPILE_FLAGS "--target=arm-openadk-linux-uclibceabihf  ${CROSS_MACHINE_FLAGS} --gcc-toolchain=${MY_GCC_TOOLCHAIN}/usr")

set(MY_COMMON_LINKER_FLAGS "--target=arm-openadk-linux-uclibceabihf -B ${MY_GCC_TOOLCHAIN}/usr/arm-openadk-linux-uclibceabihf/bin -fuse-ld=bfd -L${MY_GCC_TOOLCHAIN}/usr/lib -L${MY_GCC_TOOLCHAIN}/usr/lib/gcc/arm-openadk-linux-uclibceabihf/7.2.0 --gcc-toolchain=${MY_GCC_TOOLCHAIN}/usr")

set(CMAKE_C_COMPILER ${MY_CLANG_TOOLCHAIN}/usr/bin/clang)

set(CMAKE_CXX_COMPILER ${MY_CLANG_TOOLCHAIN}/usr/bin/clang++)

set(CMAKE_C_FLAGS       "-fwrapv -fno-ident ${MY_COMMON_COMPILE_FLAGS} " CACHE STRING "OpenADK CFLAGS" FORCE)

set(CMAKE_CXX_FLAGS     "-fwrapv -fno-ident -stdlib=libstdc++ -I${MY_GCC_TOOLCHAIN}/usr/arm-openadk-linux-uclibceabihf/include/c++/7.2.0 -I${MY_GCC_TOOLCHAIN}/usr/arm-openadk-linux-uclibceabihf/include/c++/7.2.0/arm-openadk-linux-uclibceabihf ${MY_COMMON_COMPILE_FLAGS}" CACHE STRING "OpenADK CXXFLAGS" FORCE)

set(CMAKE_EXE_LINKER_FLAGS    ${MY_COMMON_LINKER_FLAGS} CACHE STRING "OpenADK LDFLAGS" FORCE)

set(CMAKE_MODULE_LINKER_FLAGS ${MY_COMMON_LINKER_FLAGS} CACHE STRING "OpenADK LDFLAGS" FORCE)

set(CMAKE_SHARED_LINKER_FLAGS ${MY_COMMON_LINKER_FLAGS} CACHE STRING "OpenADK LDFLAGS" FORCE)

set(CMAKE_STATIC_LINKER_FLAGS ${MY_COMMON_LINKER_FLAGS} CACHE STRING "OpenADK LDFLAGS" FORCE)

set(MY_SYSTEM_INCLUDE_DIRS ${MY_GCC_TOOLCHAIN}/usr/arm-openadk-linux-uclibceabihf/include/c++/7.2.0 ${MY_GCC_TOOLCHAIN}/usr/arm-openadk-linux-uclibceabihf/include/c++/7.2.0/arm-openadk-linux-uclibceabihf)

set(CMAKE_INSTALL_SO_NO_EXE 0)

set(CMAKE_PROGRAM_PATH "/Volumes/CASE/my-os-pi3/host_x86_64-apple-darwin16.7.0/usr/bin")

set(CMAKE_SYSROOT "/Volumes/CASE/my-os-pi3/target_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf")

set(CMAKE_FIND_ROOT_PATH "/Volumes/CASE/my-os-pi3/target_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf")

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)

set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)

set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

set(ENV{PKG_CONFIG_SYSROOT_DIR} "/Volumes/CASE/my-os-pi3/target_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf")

set(ENV{PKG_CONFIG_LIBDIR} "/Volumes/CASE/my-os-pi3/target_raspberry-pi3-cm_uclibc-ng_cortex_a53_hard_eabihf/usr/lib/pkgconfig:@@STAGING_TARGET_DIR@@/usr/share/pkgconfig")

Note: First I tried using -fuse-ld=lld but it can not build the final app: it keeps searching in /lib/ on my host for libc.so.1 and 2 other libs(uclibc libs). If I then add -nostdlib then cmake can compile his testprograms for C and C++. And then all the shared libs of my app build fine, except when linking the final application with all of these libs, it does not find some cxx11 strings and sigint functions: it indicates several undefined references. Weird because I say -stdlib=libstdc++, and those undefined references look like libc++ ones.

So I switched to using the standard “bfd” linker and this compiles and links my libs+app fine.  Compilation time is now down to 2 minutes, so I already like it ;)

But, running it failed, but the only thing that I had to do was add a symlink /lib/ld-linux-armhf.so.3 pointing to /lib/ld-uClibc-1.0.26.so and then it runs on my target system. 

When I run it, it all seems to work, but an exception thrown from within one of the shared libraries is not caught in the main application. It just hangs there at that particular line. So I tried with the regular toolchain.cmake file (which uses gcc) and there that also didn’t work.

So then I removed the "-fomit-frame-pointer -fno-unwind-tables -fno-asynchronous-unwind-tables” options(hardcoded in vars.mk) and rebuild my entire os. Then using the gcc toolchain, it worked fine, and the exception coming from the shared lib was caught in the main application.

But trying that now with the clang toolchain, it still hangs in the shared lib… So try-catch and exceptions work inside these libs, but when one is uncaught, it just hangs there.

So now I have the situation where it almost works, but these exceptions are now the only remaining problem I have. Any clues what could be wrong still?

Thanks

Best regards,

Tom,