CODEWITHSUNDEEP
cmake
nowox
nowox

Reputation: 29096

How do I get a verbose output for CMake?

I would like to investigate why I have this error:

$ cmake ..
-- The C compiler identification is unknown
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /cygdrive/c/Users/Ycr/Home/bin/arm-none-eabi-gcc
-- Check for working C compiler: /cygdrive/c/Users/Ycr/Home/bin/arm-none-eabi-gcc -- broken
CMake Error at /usr/share/cmake-3.6.2/Modules/CMakeTestCCompiler.cmake:61 (message):
  The C compiler "/cygdrive/c/Users/Ycr/Home/bin/arm-none-eabi-gcc" is not
  able to compile a simple test program.

Unfortunately after the error:

How should I investigate such an error?

I tried to use the --debug-trycompile option. This time CMake creates a CMakeTmp folder which makes perfectly without errors. However, I still have this CMakeFiles/cmTC_e4aa4.dir that generates errors and even with the option CMake unlinks the folder.

Upvotes: 8

Views: 16584

Answers (2)

Frederik
Frederik

Reputation: 719

For me, none of the log files in my output directory contained useful information from try_compile(), even when using --debug-trycompile.

I ended up using the OUTPUT_VARIABLE option to capture and then print the output like this:

try_compile(<options> OUTPUT_VARIABLE TRY_COMPILE_OUTPUT)

message(WARNING ${TRY_COMPILE_OUTPUT})

Upvotes: 4

Florian
Florian

Reputation: 42852

Getting a Verbose Log

The try_compile() calls that CMake does in the beginning to test the compiler, gives a detailed error output on the console and writes it to

[your binary output directory]/CMakeFiles/CMakeError.log

I've checked the source code again and there is no CMake option that would give more a more detailed output for CMake's internal try_compile() calls.

You could just force the output to standard output by adding some variable_watch() calls to your main CMakeLists.txt before your project() call like:

variable_watch(__CMAKE_C_COMPILER_OUTPUT)
variable_watch(__CMAKE_CXX_COMPILER_OUTPUT)

Keeping the Temporary Files

To keep the temporary file of try_compile, add --debug-trycompile to the cmake command line.

But be aware that the multiple compiler tests at the beginning overwrite the artifacts of previous ones:

It may however change the results of the try-compiles as old junk from a previous try-compile may cause a different test to either pass or fail incorrectly. This option is best used for one try-compile at a time, and only when debugging.

References

Upvotes: 6

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