CMake cannot find `arm-none-eabi-g++`

[ProExpertProg]

On a linux system (Ubuntu 18.04 WSL).

I installed all the dependencies, and am performing step 7 of this guide.

This is the error I'm getting.

CMake Error at mbed-cmake/CMakeLists.txt:35 (project):
  The CMAKE_C_COMPILER:

    arm-none-eabi-gcc

  is not a full path and was not found in the PATH.

  Tell CMake where to find the compiler by setting either the environment
  variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to
  the compiler, or to the compiler name if it is in the PATH.

CMake Error at mbed-cmake/CMakeLists.txt:35 (project):
  The CMAKE_CXX_COMPILER:

    arm-none-eabi-g++

  is not a full path and was not found in the PATH.

  Tell CMake where to find the compiler by setting either the environment
  variable "CXX" or the CMake cache entry CMAKE_CXX_COMPILER to the full path
  to the compiler, or to the compiler name if it is in the PATH.

I've added the bin folder of the Arm toolchain to the path in .bashrc, .bash_profile, and .profile.

I've added the following lines in cmake, just above include(mbed_gcc_arm_toolchain):

...
message(STATUS "PATH:")
message(STATUS $ENV{PATH})

include(mbed_gcc_arm_toolchain)

project(mbed-cmake LANGUAGES C CXX ASM)
...

Which print

-- PATH:
-- /usr/share/gcc-arm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

This makes me think cmake only has access to .profile, which is reasonable to me. Still, the PATH clearly contains the path to the Arm toolchain; if I perform

$ ls /usr/share/gcc-arm/bin

I get:

arm-none-eabi-addr2line  arm-none-eabi-elfedit    arm-none-eabi-gcc-ranlib     arm-none-eabi-gdb-add-index-py  arm-none-eabi-objcopy  arm-none-eabi-strip
arm-none-eabi-ar         arm-none-eabi-g++        arm-none-eabi-gcov           arm-none-eabi-gdb-py            arm-none-eabi-objdump
arm-none-eabi-as         arm-none-eabi-gcc        arm-none-eabi-gcov-dump      arm-none-eabi-gprof             arm-none-eabi-ranlib
arm-none-eabi-c++        arm-none-eabi-gcc-9.3.1  arm-none-eabi-gcov-tool      arm-none-eabi-ld                arm-none-eabi-readelf
arm-none-eabi-c++filt    arm-none-eabi-gcc-ar     arm-none-eabi-gdb            arm-none-eabi-ld.bfd            arm-none-eabi-size
arm-none-eabi-cpp        arm-none-eabi-gcc-nm     arm-none-eabi-gdb-add-index  arm-none-eabi-nm                arm-none-eabi-strings

Googling the error itself did not give me any useful feedback. I'd appreciate any pointers!

[jay-sridharan]

What's the result when you run which arm-none-eabi-g++? Just to make sure that the compiler is actually in your path.

[multiplemonomials]

Also is this from CLion, or from the command line?

[ProExpertProg]

Both command line and CLion; they had different PATHs but they both contained /usr/share/bin.

When I run which arm-none-eabi-g++, I get /usr/local/bin/arm-none-eabi-gcc.

I resolved this issue by setting the compilers explicitly using -DCMAKE_C_COMPILER=/usr/local/bin/arm-none-eabi-gcc -DCMAKE_CXX_COMPILER=/usr/local/bin/arm-none-eabi-g++. In CLion, that can be achieved by setting the toolchain directly.

When you set the toolchain directly, make sure that include(mbed_gcc_arm_toolchain) happens before any project() calls; otherwise, you might get an error in terms of

The C compiler
    "/usr/local/bin/arm-none-eabi-gcc"
  is not able to compile a simple test program.

which happens because CMake is testing the compiler before you set the required options.

[ProExpertProg]

While the solution above works, it fails later in the build process because it fails to find other arm-none-eabi-* files.

A better solution is making sure that the correct path gets added to PATH. This issue might be unique to CLion on Windows using WSL:

When CLion runs CMake, it does not read .bashrc. Instead, it only gets its PATH from /etc/environment. Hence, if you add the bin directory of arm-none-eabi to the definition there, CMake will be able to access all of the toolchain executables.

Be careful: /etc/environment contains important path definitions (to things like ls,cp,mount), so if you mess it up, you won't be able to access them.

Thank you @multiplemonomials and @jayasurya-sridharan!

[Narzog]

I have tried all the solutions above and have the same errors and it still wouldn't recognize the compiler.