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

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)

Answer 1

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 with a proper C standard library, you don't have printf, or _start or _exit or similar, passing arguments to main is implementation-defined, or you need a special linker script, or 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 an executable, as explained in cmake docs CMAKE_TRY_COMPILE_TARGET_TYPE. This avoids running the linker and is intended for cross-compiling.
You can set CMAKE_C_COMPILER_WORKS and it will omit the check in CMakeTestCCompiler.cmake, but CMAKE_TRY_COMPILE_TARGET_TYPE is a more proper solution.

Answer 2

Well this problem is really annoying, i faced this issue for 2 day now I got solution.
Let me explain my issue first
When I delete NDK and Cmake from Sdk folder and Run my application then grable install NDK and Cmake again.
Only that time Application run and when try to run again i get this error The C Compiler is not able to compile a simple test program.
Before i was using ndkVersion "22.0.7026061" then change to thisndkVersion "21.1.6352462" and IT WORKED.
I think this is NDK problem and most of answer are outdated try this i hope this will HELP.

Answer 3

If using CMake GUI, you can add a boolean entry named
CMAKE_CXX_COMPILER_FORCED
then set it to True.
This will skip checking process for this build.

Answer 4

Ran into the same problem while re-compiling a project. Turned out that the compiler had been updated in the meantime.
After removing the build directory and creating it again, the compilation completed without errors.