CMake Command Line Definitions Not Perpetuating To Toolchain File

Question

I have a cmake cross compiler toolchain file, abridged as:

set(CMAKE_SYSTEM_NAME Linux)
if( DEFINED TC_PATH )
    message( STATUS " TC_PATH IS defined. ${TC_PATH}" )
else()
    message( FATAL_ERROR " TC_PATH not defined." )
endif()

set(CMAKE_C_COMPILER ${TC_PATH}/usr/bin/i586-linux/i586-linux-gcc )
set(CMAKE_CXX_COMPILER ${TC_PATH}/usr/bin/i586-linux/i586-linux-g++ )
set(CMAKE_LINKER ${TC_PATH}/usr/bin/i586-linux/i586-linux-ld )

I call cmake, setting the TC_PATH as well as the toolchain file:

~/CMakeTest/output $ cmake -DTC_PATH:PATH=/opt/toolchain -DCMAKE_TOOLCHAIN_FILE=../toolchain.cmake ../

It appears cmake is invoking the toolchain file multiple times. On the first two time, the TC_PATH check succeeds, but later, after identifying the compilers, it throws an error:

--  TC_PATH IS defined. /opt/toolchain
--  TC_PATH IS defined. /opt/toolchain
-- The C compiler identification is GNU 4.9.1
-- The CXX compiler identification is GNU 4.9.1
-- Check for working C compiler: /opt/toolchain/usr/bin/i586-linux/i586-linux-gcc
CMake Error at /home/gnac/CMakeTest/toolchain.cmake:4 (message):
   TC_PATH not defined.
Call Stack (most recent call first):
  /home/gnac/CMakeTest/output/CMakeFiles/3.0.2/CMakeSystem.cmake:6 (include)
  CMakeLists.txt:2 (project)

So, outside of setting a permanent environment variable in the shell, how I can set the TC_PATH variable via the command line so that it will be remain in context while executing the cmake generate command?

Answer 1

When compiling a test project, CMake does not pass variables to it by default.

There is CMAKE_TRY_COMPILE_PLATFORM_VARIABLES option for passing variables into the test project. In order to fix your issue, this line should be put into the toolchain file:

set(CMAKE_TRY_COMPILE_PLATFORM_VARIABLES TC_PATH)