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I am trying to cross-compile a project for embedded ARM Cortex builds, but I am unable to get the linker working. I want to use armlink, but no files are passed to armlink and hence no .elf file is produced.

My CMakeLists.txt is pretty simple and given below. The failure is shown after that which shows that armlink was invoked by the makefile without any arguments.

Any pointers will help - I searched and read many posts, but they all seem to have more involved requirements.

cmake_minimum_required(VERSION 2.8) project(test_arm) enable_language(C ASM) # Cross-compilation for ARM SET(CMAKE_C_COMPILER armcc) SET(CMAKE_LINKER armlink) SET(CMAKE_C_LINK_EXECUTABLE armlink) SET(CMAKE_C_FLAGS "--cpu=Cortex-M3") SET(LINK_FLAGS "--map --ro-base=0x0 --rw-base=0x0008000 --first='boot.o(RESET)' --datacompressor=off") SET(CMAKE_EXE_LINKER_FLAGS "--map --ro-base=0x0 --rw-base=0x0008000 --first='boot.o(RESET)' --datacompressor=off") include_directories(../include) add_executable(blinky blinky.c) set_target_properties(blinky PROPERTIES LINKER_LANGUAGE C)

The failure is as follows, but I guess it would be obvious to someone given that I have some stupid issue in my CMakeLists:

$ make VERBOSE=1 [100%] Building C object CMakeFiles/blinky.dir/blinky.c.o /usr/bin/cmake -E cmake_link_script CMakeFiles/blinky.dir/link.txt --verbose=1 armlink Linking C executable blinky Product: DS-5 Professional 5.21.0 [5210017] Component: ARM Compiler 5.05 update 1 (build 106) Tool: armlink [4d0efa] For support see http://www.arm.com/support/ Software supplied by: ARM Limited Usage: armlink option-list input-file-list where ....

I was expecting the CMake generated Makefile to invoke armlink with something like:

armlink --map --ro-base=0x0 --rw-base=0x0008000 \ --first='boot.o(RESET)' --datacompressor=off \ CMakeFiles/blinky.dir/blinky.c.o -o blinky.elf
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3 Answers 3

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Starting with CMake v3.5 you don't need a toolchain anymore for Keil ARM C/C++ compilation tools:

Support was added for the ARM Compiler (arm.com) with compiler id ARMCC.

Just set your C/CXX compiler variables accordingly

cmake -DCMAKE_C_COMPILER:PATH="C:\Program Files (x86)\DS-5\bin\armcc.exe" -DCMAKE_CXX_COMPILER:PATH="C:\Program Files (x86)\DS-5\bin\armcc.exe" ...

References

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Comments

1

From my experience, you cannot set CMAKE_EXE_LINKER_FLAGS in a CMakeLists.txt file. It has to be passed via a CMAKE_TOOLCHAIN_FILE when CMake is invoked the very first time in a build directory.

I don't find any documentation regarding this problem, but there is the cross-compilation with CMake page which you should use it if you do cross-compilation.

For a start, just put your set-calls in a toolchain file and run

cmake -DCMAKE_TOOLCHAIN_FILE=<yourfile.toolchain>

in a clean build directory.

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Thanks Patrick. I tried this but didn't make progress. I went through the page and created a toolchainfile and passed on command-line as you wrote above. I still couldn't get the linker to work. I did start from a clean build directory. Any more ideas?
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A toolchain file may be a good idea. Here is what I've came up the last time I tried CMake 2.8.10 with the DS-5 toolchain (it could still be optimized, but it should give you a starting point):

INCLUDE(CMakeForceCompiler) # This one is important SET(CMAKE_SYSTEM_NAME Generic) SET(CMAKE_SYSTEM_PROCESSOR arm) # Specify the cross compiler SET(CMAKE_C_COMPILER "C:/Program Files (x86)/DS-5/bin/armcc.exe") SET(CMAKE_CXX_COMPILER "C:/Program Files (x86)/DS-5/bin/armcc.exe") SET(CMAKE_AR "C:/Program Files (x86)/DS-5/bin/armar.exe" CACHE FILEPATH "Archiver") #CMAKE_FORCE_C_COMPILER("C:/Program Files (x86)/DS-5/sw/gcc/bin/arm-linux-gnueabihf-gcc.exe" GNU) #CMAKE_FORCE_CXX_COMPILER("C:/Program Files (x86)/DS-5/sw/gcc/bin/arm-linux-gnueabihf-g++.exe" GNU) UNSET(CMAKE_C_FLAGS CACHE) SET(CMAKE_C_FLAGS "--cpu=Cortex-A9 --thumb -Ospace" CACHE STRING "" FORCE) UNSET(CMAKE_CXX_FLAGS CACHE) SET(CMAKE_CXX_FLAGS ${CMAKE_C_FLAGS} CACHE STRING "" FORCE) UNSET(CMAKE_EXE_LINKER_FLAGS CACHE) SET(CMAKE_EXE_LINKER_FLAGS "" CACHE STRING "" FORCE) UNSET(CMAKE_AR_FLAGS CACHE) SET(CMAKE_AR_FLAGS "-p -armcc,-Ospace" CACHE STRING "" FORCE) # set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> cr <TARGET> <LINK_FLAGS> <OBJECTS>") SET(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> ${CMAKE_AR_FLAGS} -o <TARGET> <OBJECTS>" CACHE STRING "C Archive Create") # set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> cr <TARGET> <LINK_FLAGS> <OBJECTS>") SET(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> ${CMAKE_AR_FLAGS} -o <TARGET> <OBJECTS>" CACHE STRING "CXX Archive Create") include_directories("C:/Program Files (x86)/DS-5/include") #include_directories("C:/Program Files (x86)/DS-5/sw/gcc/arm-linux-gnueabihf/libc/usr/include/arm-linux-gnueabi") # Where is the target environment SET(CMAKE_FIND_ROOT_PATH "C:/Program Files (x86)/DS-5") # Search for programs in the build host directories SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER) # For libraries and headers in the target directories SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY) SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

Regarding your question

Some failure analysis

What you have tried should work (see also e.g. How do I add a linker or compile flag in a CMake file?). But it seems something goes wrong during the configuration step.

I don't know your command line call for CMake's configuration/generation steps, so some general tips to find the root cause:

You could try calling

cmake.exe --trace ...

to see what went wrong with your CMAKE_EXE_LINKER_FLAGS variable. This will generate a lot of output, so here are some basics on what CMake does:

  • The project() command will trigger the compiler evaluation
  • This will write CMAKE_EXE_LINKER_FLAGS into your CMakeCache.txt
  • You are overwriting it with a local variable (see variable scope docu here)

If you look into share\cmake-2.8\Modules\CMakeCommonLanguageInclude.cmake:

set (CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS_INIT} $ENV{LDFLAGS}" CACHE STRING "Flags used by the linker.")

You could use CMAKE_EXE_LINKER_FLAGS_INIT, but you have to set it before the project() command or in the toolchain file.

Because you set the link language to C take a look into share\cmake-2.8\Modules\CMakeCInformation.cmake:

if(NOT CMAKE_C_LINK_EXECUTABLE) set(CMAKE_C_LINK_EXECUTABLE "<CMAKE_C_COMPILER> <FLAGS> <CMAKE_C_LINK_FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>") endif()

So you can use CMAKE_C_LINK_EXECUTABLE to overwrite the complete linker call or you could use CMAKE_C_LINK_FLAGS to set additional flags.

The "official" way

The official way to set the target's linker and compiler flags would be (before CMake 2.8.12):

set_property(TARGET blinky APPEND_STRING PROPERTY COMPILE_FLAGS "--cpu=Cortex-M3") set_property(TARGET blinky APPEND_STRING PROPERTIES LINK_FLAGS "--map --ro-base=0x0 --rw-base=0x0008000 --first='boot.o(RESET)' --datacompressor=off")

Starting with CMake 2.8.12 it would be something like:

add_compile_options("--cpu=Cortex-M3")
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7 Comments

Thanks Florian for the detailed reply. I have spent hours on this but no progress yet. I can't even get the armcc to work. Complains that it is unable to compile even a simple program. I started using a toolchain file and added SET(CMAKE_C_LINK_EXECUTABLE="<CMAKE_LINKER> <FLAGS> ${CMAKE_C_LINK_FLAGS} <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>") but that didn't help.
OK, one more question. I realize that I need to build my SET(CMAKE_C_COMPILE_OBJECT "<CMAKE_C_COMPILER> ${....) to be able to compile with the forced compiler. But how do I make it utilize the include_directories??
I'm sorry to hear it didn't work. But I'm confident we could find a solution that will work.
If you have problems with the "unable to compile a simple program" error, you should add --debug-trycompile to your cmake.exe command line options. This will keep CMakeFiles\CMakeTmp directory to check the compiler runs outputs (including a log file). And I was using Ninja as an replacement for ARM's make, because it gives a detailed output of what it had tried (full command line call I can copy/paste on the command line for tests; was very helpful; also check it's rules.ninja file). And please add some more details on the errors you get.
And for your first tests - not recommended as the final solution - you could add the following two lines to your toolchain file to bypass the CMake's own compiler tests: SET(CMAKE_C_COMPILER_WORKS 1 CACHE INTERNAL "") and SET(CMAKE_CXX_COMPILER_WORKS 1 CACHE INTERNAL ""). Additionally - to make sure that the variables set in toolchain file are what you end up in your compiler call - you can/should add CACHE ... FORCE to the set() commands. For more details see stackoverflow.com/questions/11423313/…
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