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

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


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Comment at: clang-tidy/hicpp/ExceptionBaseclassCheck.cpp:41
+                                              "'std::exception'")
+      << BadThrow->getSubExpr()->getType() << BadThrow->getSourceRange();
 
----------------
JonasToth wrote:
> aaron.ballman wrote:
> > Can you add a test that uses a rethrow? e.g.,
> > ```
> > try {
> >   throw 12; // Diagnose this
> > } catch (...) {
> >   throw; // Does not diagnose this
> > }
> > ```
> I added this case, but i have questions on this one.
> 
> The type of the caught exception is not know in general right? 
> In this case, a deeper analysis would find that the second `throw` is problematic, too.
> But since the rethrow depends on the original thrown type, conforming code could never rethrow a bad exception.
I think it's fine to not diagnose the rethrow -- as you mentioned, the only way for it to be a problem is when the original throw is a problem and that will get diagnosed elsewhere.


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Comment at: test/clang-tidy/hicpp-exception-baseclass.cpp:9
+class deep_hierarchy : public derived_exception {};
 class non_derived_exception {};
 
----------------
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`.


https://reviews.llvm.org/D37060