series of warnings from flycheck with cmake.3.6.2, gcc.6.x and llvm-4.0.0.

[vibrys]

Hi.
I'm trying to configure cmake-ide (through spacemacs-cmake-ide layer) into fairly large C++ project.
Project uses cmake to generate Makefile, then gcc.6.2.1 is used to compile the project.

Looks like rtags and irony works ok, but I have problems with flycheck.

When I visit some *.cpp file I get the following error from flycheck:

         Suspicious state from syntax checker c/c++-clang: Flycheck checker c/c++-clang returned non-zero exit code 1, but its output contained no errors: error: unknown warning option '-Wuseless-cast'
         error: unknown warning option '-Wlogical-op'; did you mean '-Wlong-long'?
         error: unknown warning option '-Wstrict-null-sentinel'
         error: unknown warning option '-Wformat-signedness'
         error: unknown warning option '-Wlogical-op'; did you mean '-Wlong-long'?
         error: unknown warning option '-Wduplicated-cond'; did you mean '-Wduplicate-enum'?
         error: unknown warning option '-Wshift-overflow=2'; did you mean '-Wshift-overflow'?
         error: unknown warning option '-Werror=cpp'

to workaround the problem I've just added extra filter to cmake-ide-set-compiler-flags function:
(setq flycheck-clang-args (cmake-ide--filter (lambda (x) (not (string-match "\\(-Wlogical-op\\|-Wuseless-cast\\|-Wstrict-null-sentinel\\|-Wformat-signedness\\|-Wduplicated-cond\\|-Wshift-overflow=[0-9]+\\|-Werror\\|-Wno-error=cpp\\)" x))) flycheck-clang-args))

Since then, the flycheck at least started working, ie I could see some error highlighted throughout the buffer.

There are three cases with it.
1st: if it is legal/used at all to use c/c++-clang flycheck checker to syntax check project that takes flags from gcc to use it by clang? I mean, do the people use cmake-ide's syntax checking for such projects?

2nd: If Yes, then do You think the errors above are rather llvm ones?

3rd: Is there any better solution for the workaround?

best regards,

Mat

[atilaneves]

My guess is that your project sets compiler flags assuming gcc. I'd fix the CMake build of it to use compiler-appropriate flags. I don't think there's much that can be done on cmake-ides end of this story.