[PATCH] D37060: [clang-tidy] Improve hicpp-exception-baseclass to handle generic code better

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added subscribers: sbenza, klimek.
aaron.ballman added inline comments.


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Comment at: test/clang-tidy/hicpp-exception-baseclass.cpp:9
+class deep_hierarchy : public derived_exception {};
 class non_derived_exception {};
 
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JonasToth wrote:
> aaron.ballman wrote:
> > JonasToth wrote:
> > > aaron.ballman wrote:
> > > > JonasToth wrote:
> > > > > aaron.ballman wrote:
> > > > > > Can you add a test that uses multiple inheritance? e.g.,
> > > > > > ```
> > > > > > class terrible_idea : public non_derived_exception, public derived_exception {};
> > > > > > ```
> > > > > > Also, is private inheritance also acceptable, or does it need to be public inheritance? I kind of get the impression it needs to be public, because the goal appears to be that you should always be able to catch a `std::exception` instance, and you can't do that if it's privately inherited. That should have a test as well.
> > > > > The rules do not state directly, that it must be inherited public, but i dont see a good reason to allow non-public inheritance.
> > > > > Another thing is, that you can always call `e.what()` on public derived exceptions.
> > > > > 
> > > > > Multiple inheritance is harder, since the type is still a `std::exception`. One could catch it and use its interface, so these reasons are gone to disallow it.
> > > > > The rules do not state directly, that it must be inherited public, but i dont see a good reason to allow non-public inheritance.
> > > > 
> > > > Agreed.
> > > > 
> > > > > Another thing is, that you can always call e.what() on public derived exceptions.
> > > > 
> > > > Agreed.
> > > > 
> > > > > Multiple inheritance is harder, since the type is still a std::exception. One could catch it and use its interface, so these reasons are gone to disallow it.
> > > > 
> > > > I think the multiple inheritance case should not diagnose because it meets the HIC++ requirement of being derived from `std::exception`.
> > > I have a problem with implementing the inheritance rules.
> > > 
> > > From the Matchers, there seems to be no way to test, if the inheritance is public. Should i work a new matcher for that, or rather move the tests, if the type holds all conditions into the callback function. This would mean, that every `throw` gets matched.
> > I would say you can handle private inheritance in a follow-up patch. I would look into changing the `isPublic()` (and related) matchers to handle inheritance (might as well handle `isVirtual()` at the same time, too), though I've not given this interface a ton of thought.
> Ok. I will commit this one with according FIXME: sections and will `#if 0` the currently offending check-messages.
> 
> from the usability, something like:
> `isSameOrDerivedFrom("std::exception", isPublic())` would be nice, but i dont know if this is even possible.
> In that sense, the other modifiers could be used as well (`isVirtual()`, `isProtected()`...).
I'm not too certain (maybe @klimek or @sbenza knows more), but I think you can modify `isDerivedFrom()` to accept an additional matcher so that could can write `isDerivedFrom(hasName("X"), allOf(isPublic(), isVirtual()))` and then thread that change through to the other derived matchers. I would guess this means `isPublic()` (et al) would need to accept a `CXXBaseSpecifier` as well as the declarations they currently accept.


https://reviews.llvm.org/D37060