CMake: The C Compiler is not able to compile a simple test program

Question

I am trying to cross-compile the Azure IoT SDK C for a Mips processor. Cross-compiling an older version of the same SDK using an older version of CMake (2.8.12.2) works just fine, so I doubt it's the code itself. I am guessing it's the Mips GCC compiler.

Error message:

CMake Error at /usr/share/cmake-3.10/Modules/CMakeTestCCompiler.cmake:52 (message):
  The C compiler

    "/usr/local/mipsisa32r2el/r23/bin/mipsisa32r2el-axis-linux-gnu-gcc"

  is not able to compile a simple test program.

  It fails with the following output:

    Change Dir: /home/axis/azure-iot-sdk-c/cmake/iotsdk_linux/CMakeFiles/CMakeTmp

    Run Build Command:"/usr/bin/make" "cmTC_2cc84/fast"
    /usr/bin/make -f CMakeFiles/cmTC_2cc84.dir/build.make CMakeFiles/cmTC_2cc84.dir/build
    make[1]: Entering directory '/home/axis/azure-iot-sdk-c/cmake/iotsdk_linux/CMakeFiles/CMakeTmp'
    Building C object CMakeFiles/cmTC_2cc84.dir/testCCompiler.c.o
    /usr/local/mipsisa32r2el/r23/bin/mipsisa32r2el-axis-linux-gnu-gcc --sysroot=/usr/local/mipsisa32r2el/r23    -o CMakeFiles/cmTC_2cc84.dir/testCCompiler.c.o   -c /home/axis/azure-iot-sdk-c/cmake/iotsdk_linux/CMakeFiles/CMakeTmp/testCCompiler.c
    Linking C executable cmTC_2cc84
    /usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_2cc84.dir/link.txt --verbose=1
    /usr/local/mipsisa32r2el/r23/bin/mipsisa32r2el-axis-linux-gnu-gcc --sysroot=/usr/local/mipsisa32r2el/r23      -rdynamic CMakeFiles/cmTC_2cc84.dir/testCCompiler.c.o  -o cmTC_2cc84 
    /usr/local/mipsisa32r2el/r23/lib/gcc/mipsisa32r2el-axis-linux-gnu/4.7.2/../../../../mipsisa32r2el-axis-linux-gnu/bin/ld: this linker was not configured to use sysroots
    collect2: error: ld returned 1 exit status
    CMakeFiles/cmTC_2cc84.dir/build.make:97: recipe for target 'cmTC_2cc84' failed
    make[1]: *** [cmTC_2cc84] Error 1
    make[1]: Leaving directory '/home/axis/azure-iot-sdk-c/cmake/iotsdk_linux/CMakeFiles/CMakeTmp'
    Makefile:126: recipe for target 'cmTC_2cc84/fast' failed
    make: *** [cmTC_2cc84/fast] Error 2

Unfortunately, I am stuck with the Mips GCC compiler I have. Is there a way to disable this test-program check?

Solution was to add these to the toolchain-file:

SET (CMAKE_C_COMPILER_WORKS 1)
SET (CMAKE_CXX_COMPILER_WORKS 1)

"Is there a way to disable this test-program check?" - Yes. Easily googled: stackoverflow.com/questions/10599038/… — Tsyvarev
@Tsyvarev Ignored it because the accepted answer is from 2012 with no usable answer, but down at the bottom there's a line that seems to disable it. — Kagemand Andersen
If your last paragraph has intention answer your question, then it is not right place for it: on Stack Overflow we tend to separate question and answer posts. Instead, you may your answer it into the answer post: on Stack Overflow self-answering is perfectly acceptible. — Tsyvarev
@Tsyvarev I know, but thought the 48 period also applied to posting it, not just to accepting it. Also someone might have a better solution, or just one with an explanation. — Kagemand Andersen

KamilCuk KamilCuk · Accepted Answer · 2018-12-05T15:07:37

CMake tries to compile an executable using "standard" (as per what CMake thinks is standard) compiler options and tries to run that executable, so to see if the compiler is working. The executable is simple like int main(int argc, char *argv[]) { return argc - 1; }.

You can't do that when cross-compiling. Because usually you can't link a proper standard C library, you don't have printf, or _start or _exit or similar, passing arguments to main is implementation-defined, or you need a linker script or you there's no emulator for your architecture so can't run cross-compiled source on the host, etc... Simply: you usually can't run the cross-compiled executable on the host and most of the time even the compilation is hard enough to do.

The common solution is to set before project():

set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")

So that CMake will try to compile a static library not a executable, as explained here. This avoids running the linker and is intended for cross-compiling.

You can set CMAKE_C_COMPILER_WORKS and it will omit the check per here, but I feel the CMAKE_TRY_COMPILE_TARGET_TYPE is a more proper solution.

CMake: The C Compiler is not able to compile a simple test program

3 Answers