Re: Run unit tests with C++ too

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, May 01, 2024 at 03:38:10PM +0100, Ferruh Yigit wrote:
> On 5/1/2024 3:14 PM, Mattias Rönnblom wrote:
> > On 2024-05-01 11:10, Ferruh Yigit wrote:
> >> On 4/30/2024 9:57 PM, Patrick Robb wrote:
> >>>
> >>>
> >>> On Tue, Apr 30, 2024 at 4:13 PM Mattias Rönnblom <hofors@lysator.liu.se
> >>> <mailto:hofors@lysator.liu.se>> wrote:
> >>>
> >>>      On 2024-04-30 15:52, Patrick Robb wrote:
> >>>      >
> >>>      >
> >>>      > On Sun, Apr 28, 2024 at 3:46 AM Mattias Rönnblom
> >>>      <hofors@lysator.liu.se <mailto:hofors@lysator.liu.se>
> >>>      > <mailto:hofors@lysator.liu.se <mailto:hofors@lysator.liu.se>>>
> >>> wrote:
> >>>      >
> >>>      >     It would be great if the unit test suite (app/test/*) was
> >>>      compiled (and
> >>>      >     run) using a C++ (C++11) compiler as well. At least, if
> >>> such is
> >>>      >     available.
> >>>      >
> >>>      >
> >>>      > Sure, the UNH Lab can try this.
> >>>      >
> >>>      >
> >>>      >     With the current state of affairs, header file macros or
> >>>      functions are
> >>>      >     not verified to be functional (or even valid) C++.
> >>>      >
> >>>      >     "C is a subset of C++", which was never true, is becoming
> >>> less and
> >>>      >     less so.
> >>>      >
> >>>      >     If all unit tests aren't valid C++, maybe one could start
> >>> with
> >>>      an "opt
> >>>      >     in" model.
> >>>      >
> >>>      >
> >>>      > Okay, so basically run the fast-test suite, record all that don't
> >>>      pass,
> >>>      > submit a bugzilla ticket stating which unit tests are not
> >>> valid on a
> >>>      > certain c++ compiler, then bring CI Testing online using the
> >>> valid
> >>>      > subset of fast-tests. This should work.
> >>>      >
> >>>
> >>>      Sounds good.
> >>>
> >>>      Just to be clear: the above includes extending the DPDK build
> >>> system to
> >>>      build the app/test/dpdk-test binary in two versions: one C and
> >>> one C++,
> >>>      so that anyone can run the C++ tests locally as well. Correct?
> >>>
> >>>
> >>> Okay, so now I am understanding this is not yet available. When I
> >>> responded this morning I was figuring that c++ compiler support was
> >>> available and I simply wasn't aware, and that we could quite easily set
> >>> cc={some c++ compiler}, meson would pick it up, and we would be able to
> >>> build DPDK and then run unit tests in this manner in CI testing.
> >>>
> >>> I didn't mean to suggest we would submit patches extending the build
> >>> system to this end. That's probably a little out of scope for what we
> >>> try to accomplish at the Community Lab.
> >>>
> >>> But if the aforementioned build system support is added, of course we
> >>> are willing to add that as a build environment for unit tests and report
> >>> those respective results.
> >>>   
> >>
> >> Does it have to be 'app/test/dpdk-test', why not build examples with C++?
> >>
> > 
> > The unit tests have the ability to test DPDK, which is exactly what we
> > want to do here. Such testing isn't limited to "compiles yes/no", but to
> > detect run-time (behavioral) issues, and properly report them.
> > 
> > This is especially important for cases where there is code only
> > exercised in C++ translation units (i.e., in #ifdef __cplusplus).
> > 
> 
> And Bruce highlighted that compile check is already covered.
> 
> Than I guess this work needs to be done in two steps,
> 1. Enable building dpdk-test (or all applications) with C++ in build
> system. And fix possible issues.
> 
> 2. Enable in dpdk-test C++ build and run in CI.
> 
> We need a volunteer for 1. before asking CI lab for 2.
> 

For testing with C++ we only need to cover code contained in header files.
Code for functions built into the DPDK .so or .a libraries will behave the
same way when called from C, C++ or any other language. It's the inline
functions in headers that will be compiled differently in C++ so we should
only look to those tests rather than trying to make the whole unit test
suite buildable via C++ IMHO.

/Bruce