cc: use '-x c*-header' for header files for C and C++ linters.

[nicopauss]

Fix #4096

When linting an header file in C or C++, -x c-header or -x c++-header should be used instead of -x c or -x c++.

Using -x c or -x c++ for headers files can lead to unused variables and functions marked as static inlined as seen in #4096.

Using -x c-header or -x c++-header solve these issues.

The list of file extensions that are considered as header files can be configured with the variables g:ale_c_cc_header_exts and g:ale_cpp_cc_header_exts.

[hsanson]

Thanks, looks good.

[laoshaw]

I use g++ as one of my linter in ale_linters

g++-11 -S -x c++-header - < test.hpp reports fatal error: cannot use ‘-’ as input filename for a precompiled header, now I have that shown in the quickfix window every time I save the header file.

the old method g++-11 -S -x c++ - < test.hpp worked flawlessly instead

[laoshaw]

Thanks, looks good.

this breaks cc as the linter badly, see above.

[nicopauss]

Oh sorry about that. I though I have tested it with GCC, but I must have messed my config while testing and only tested with clang.
I'll try to make a fix ASAP.
In the meanwhile, you can set g:cpp_cc_header_exts to []: let g:ale_cpp_cc_header_exts = []

[laoshaw]

looking for a fix, as the workaround will totally ignoring cpp headers. Thanks.

[nicopauss]

Fix here: #4334