[CMake] Can CXX_CLANG_TIDY use .clang-tidy file?

[Mateusz Loskot]

On Mon, 10 Dec 2018 at 18:31, Bill Hoffman via CMake <cmake at cmake.org> wrote:
> On 12/8/2018 7:47 PM, Mateusz Loskot wrote:
> >
> > Am I correct clang-tidy run via CXX_CLANG_TIDY
> > ignores .clang-tidy configuration file?
> >
> > I've tried number of ways to help it find the file,
> > i.e. copied the file to binary directories from where it seems run via
> > usr/local/bin/cmake -E __run_co_compile --tidy=/usr/bin/clang-tidy-7
>
> I don't think anything was done to turn that off on purpose.  Can you
> run the command from the command line and get it to work?  If so, you
> should be able to get the same arguments to the clang tidy that CMake is
> running.

Bill,

Thank you for the hint. It helped to discover it turns out to be a silly issue.

My .clang-tidy listed checks that would issue no warnings for the
target source files :)

Since, apparently, clang-tidy via
/usr/local/bin/cmake -E __run_co_compile --tidy=/usr/bin/clang-tidy-7
runs in quiet mode, while when run directly /usr/bin/clang-tidy-7,
it outputs a brief summary even if no analysis warnings are issued.
That left me with impression, .clang-tidy is not used.

To summary, for records and others looking for similar answers, here
is what works for me:

1. .clang-tidy is in source root directory

2. Top-level CMakeLists.txt

```
find_program(CLANG_TIDY
  NAMES clang-tidy-7 clang-tidy-6.0 clang-tidy-5.0 clang-tidy-4.0 clang-tidy
```

and

```
set_target_properties(test_headers_all_in_one
  PROPERTIES
    CXX_CLANG_TIDY ${CLANG_TIDY})
```

Notice, since checks are specified in .clang-tidy configuration file,
no arguments need to be specified to clang-tidy.

3. Build analysed target

```
$ cd project
$ cmake -S . -B _build -DBoost_ARCHITECTURE=-x64 ..
$ VERBOSE=1 cmake --build _build --target test_headers_all_in_one

# alternative to the last command may be

$ cd _build
$ VERBOSE=1 make test_headers_all_in_one
```

Both, will run clang-tidy with checks read from .clang-tidy config,
and output of any warnings.

Best regards,
-- 
Mateusz Loskot, http://mateusz.loskot.net