Test system for the Widl compiler

[Bernhard Kölbl]

Am Mi., 15. Juni 2022 um 20:04 Uhr schrieb Zebediah Figura
<zfigura at codeweavers.com>:
>
> On 6/15/22 12:49, Nikolay Sivov wrote:
> >
> >
> > On 6/15/22 18:20, Bernhard Kölbl wrote:
> >> Hey everyone,
> >>
> >> during the course of implementing WinRT / UWP stuff, I regularly come
> >> across missing IDL 3.0 features in our Widl compiler.
> >> Unfortunately, Widl's code seems to have grown in a rater unpleasant
> >> direction and is sometimes a real burden to understand and maintain. I
> >> think some refactoring to its code would be very well fitting and make
> >> things a lot easier for everyone, but refactoring can also bring
> >> breakage and makes tracking down errors with Git harder. Additionally,
> >> as the code is already not that small, errors have an easy way to slip
> >> in without noticing.
> >> So to me, the ideal solution seems to add a testing system to the
> >> compiler, like most of Wine's components already have.
> >>
> >> Rémi and I already outlined some ideas:
> >> - Port the Winetest system to Unix programs
> >> - Make a libwidl or Widl.exe and test against that with our current
> >> test system
> >> - Add the tests into Widl itself as callable parameter
> >>
> >> What do you think is the best solution?
> >> Getting some suggestions would be great. :)
> >
> > There are options. First it depends whether you want to validate against
> > midl or not. If you do then you'll need something like widl.exe to run
> > on Windows.

I'd personally not compare against Midl, as we already do some header
stuff differently and it also adds a bunch of "useless features".

> > Next question is what your test data would be, and how to compare the
> > output reliably with expected output. For example we don't really need
> > exact matching for generated headers, or even marshaling format strings,
> > as long as they achieve their purpose. For typelibs however, it might be
> > useful to go for exact binary match of selected sections.

My idea was to compose short snippets of some IDL feature together with
their valid output counterparts, and compare if they match after
putting the snippet in Widl.

> We already have tests for typelibs and marshalling, in oleaut32:typelib
> and oleaut32:tmarshal respectively. I see no reason that's not
> sufficient already.
>
> As far as headers are concerned, we could probably take a similar
> approach in some ways. I don't know what exactly needs testing, but we
> could do things like
>
> ok(offsetof(mystruct.field) == 16,
>          "wrong offset %u\n", offsetof(mystruct.field));
>
> or (for a compile-time assertion)
>
> extern void test(ITestInterface *obj)
> {
>      HRESULT (*myfunc)(type1 arg1, type2 *arg2, ...);
>
>      myfunc = obj->lpVtbl->myfunc;
> }

This  won't work for some WinRT features like namespaces and some attributes.

>
> Ultimately we may not need to mess with widl, or write any extra test
> infrastructure.
>