<div dir="ltr">LGTM, thanks!<div><br></div><div><br></div><div><div>+ if (RD->lookupInBases(CatchTypePublicBases::FindPublicBasesOfType, &CTPB,</div><div>+ Paths)) {</div><div>+ const CXXCatchStmt *Problem = CTPB.getFoundHandler();</div><div>+ if (!Paths.isAmbiguous(CTPB.getFoundHandlerType())) {</div></div><div><br></div><div>Is it possible that lookupInBases will find an ambiguous base (so we'll skip issuing the warning) but there is another handler for an unambiguous base? This seems like a really weird corner case (and a false negative for the warning), so don't worry about it if ambiguity is hard to detect from FindPublicBasesOfType.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Apr 7, 2015 at 7:21 AM, Aaron Ballman <span dir="ltr"><<a href="mailto:aaron@aaronballman.com" target="_blank">aaron@aaronballman.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Fri, Apr 3, 2015 at 8:44 PM, Richard Smith <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>> wrote:<br>
> Please give QualTypeExt a more specific name to indicate that it represents<br>
> a caught type. CatchHandlerType perhaps?<br>
<br>
</span>Renamed to CatchHandlerType (also changed variables named QTE).<br>
<span class=""><br>
> Please give PublicBasesOfType a name that somehow relates to catch handlers,<br>
> since it's specific to them. Also, perhaps make FindPublicBasesOfType a<br>
> static member of it, so that you don't need to provide so many public<br>
> accessors. Or maybe make PublicBasesOfType a struct, nest it inside<br>
> ActOnCXXTryBlock, and use a lambda as the callback function.<br>
<br>
</span>I changed the class name to CatchTypePublicBases, and changed<br>
FindPublicBasesOfType to be a static member. Also removed accessors<br>
that were no longer required.<br>
<span class=""><br>
> + for (const auto &P : Path) {<br>
><br>
> Do you really need to walk the path? You should get called back once for<br>
> each base class, so this seems redundant.<br>
<br>
</span>You're correct, this was redundant. I changed it over to using the<br>
CXXBaseSpecifier directly, instead of the path elements.<br>
<br>
Thanks!<br>
<span class="HOEnZb"><font color="#888888"><br>
~Aaron<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
><br>
> On Fri, Apr 3, 2015 at 5:30 PM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
> wrote:<br>
>><br>
>> Ping<br>
>><br>
>> On Sun, Mar 22, 2015 at 4:09 PM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> wrote:<br>
>> > Ping?<br>
>> ><br>
>> > On Thu, Feb 26, 2015 at 4:16 PM, Aaron Ballman <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> > wrote:<br>
>> >> Updated patch attached. Comment below.<br>
>> >><br>
>> >> On Wed, Feb 18, 2015 at 4:54 PM, Richard Smith <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>><br>
>> >> wrote:<br>
>> >>> On Tue, Feb 10, 2015 at 12:40 PM, Aaron Ballman<br>
>> >>> <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> >>> wrote:<br>
>> >>>><br>
>> >>>> On Wed, Jan 14, 2015 at 10:31 PM, Richard Smith<br>
>> >>>> <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>><br>
>> >>>> wrote:<br>
>> >>>> > + friend struct llvm::DenseMapInfo <QualTypeExt>;<br>
>> >>>> ><br>
>> >>>> > Extra space before <.<br>
>> >>>> ><br>
>> >>>> > +// It's OK to treat BaseSubobject as a POD type.<br>
>> >>>> ><br>
>> >>>> > Typo: BaseSubobject should be QualTypeExt.<br>
>> >>>><br>
>> >>>> I've fixed both those up locally.<br>
>> >>>><br>
>> >>>> ><br>
>> >>>> > + // Add direct base classes to the list of types to be<br>
>> >>>> > checked.<br>
>> >>>> > [...]<br>
>> >>>> > + RD->lookupInBases(<br>
>> >>>> ><br>
>> >>>> > lookupInBases finds all bases, not just the direct ones.<br>
>> >>>><br>
>> >>>> I must be missing something, because that doesn't seem to be entirely<br>
>> >>>> workable. When the callback function passed to lookupInBases returns<br>
>> >>>> true, searching along that path stops. See CXXInheritance.cpp:251; if<br>
>> >>>> BaseMatches returns true, we record the path but never visit further<br>
>> >>>> bases.<br>
>> >>>><br>
>> >>>> That winds up being problematic for situations like:<br>
>> >>>><br>
>> >>>> struct B {};<br>
>> >>>> struct D : B {};<br>
>> >>>> struct D2 : D {};<br>
>> >>>><br>
>> >>>> void f6() {<br>
>> >>>> try {<br>
>> >>>> } catch (B &b) { // expected-note {{for type 'HandlerInversion::B<br>
>> >>>> &'}}<br>
>> >>>> } catch (D2 &d) { // expected-warning {{exception of type<br>
>> >>>> 'HandlerInversion::D2 &' will be caught by earlier handler}}<br>
>> >>>> }<br>
>> >>>> }<br>
>> >>>><br>
>> >>>> We process the handler for B& and add it to the map. Then we process<br>
>> >>>> the handler for D2&. When we call lookupInBases on D2, we find D<br>
>> >>>> first, and since it's access is public, the callback returns true.<br>
>> >>>> The<br>
>> >>>> callback is not called a subsequent time for B as a base of D, and so<br>
>> >>>> we wind up failing to warn in that case.<br>
>> >>>><br>
>> >>>> Changing that "else if" to be an "if" is the wrong thing to do as<br>
>> >>>> well, because then a bunch of regression tests fail. I can kind of<br>
>> >>>> hack the behavior I want by having my callback not be a lambda, and<br>
>> >>>> call lookupInBases on the base class prior to returning true, but it<br>
>> >>>> feels like I'm doing something wrong. Ideas?<br>
>> >>><br>
>> >>><br>
>> >>> In Frobble, I think you should return true if you find a public path<br>
>> >>> to a<br>
>> >>> HandledType, not just if you find a public base class.<br>
>> >>><br>
>> >>>> I've attached a WIP that attempts to capture what you're suggesting<br>
>> >>>> below, but it's also causing problems with<br>
>> >>>> test\SemaCXX\unreachable-catch-clauses.cpp reporting the warning for<br>
>> >>>> the final handler twice, so it's not ready yet. Is this moving in the<br>
>> >>>> direction you were thinking (aside from obvious issues like the<br>
>> >>>> callback being named Frobble)?<br>
>> >>><br>
>> >>><br>
>> >>> Yes, thanks.<br>
>> >>><br>
>> >>>> > You should be able<br>
>> >>>> > to do something like this:<br>
>> >>>> ><br>
>> >>>> > 1) If the type is a class type, call lookupInBases, and check none<br>
>> >>>> > of<br>
>> >>>> > the<br>
>> >>>> > public unambiguous bases are in the map.<br>
>> >>>> > 2) Add the type itself to the map and diagnose if it was already<br>
>> >>>> > there.<br>
>> >>>> ><br>
>> >>>> > (and remove your explicit queue of types to process).<br>
>> >>>> ><br>
>> >>>> ><br>
>> >>>> > --- test/CXX/drs/dr3xx.cpp (revision 222171)<br>
>> >>>> > +++ test/CXX/drs/dr3xx.cpp (working copy)<br>
>> >>>> > @@ -170,9 +170,9 @@<br>
>> >>>> > void f() {<br>
>> >>>> > try {<br>
>> >>>> > throw D();<br>
>> >>>> > - } catch (const A&) {<br>
>> >>>> > + } catch (const A&) { // expected-note {{for type 'const<br>
>> >>>> > dr308::A<br>
>> >>>> > &'}}<br>
>> >>>> > // unreachable<br>
>> >>>> > - } catch (const B&) {<br>
>> >>>> > + } catch (const B&) { // expected-warning {{exception of type<br>
>> >>>> > 'const<br>
>> >>>> > dr308::B &' will be caught by earlier handler}}<br>
>> >>><br>
>> >>><br>
>> >>> Hmm, while we're here, it'd be good to strip off the 'const' and '&'<br>
>> >>> from<br>
>> >>> this diagnostic; you can't get an exception object of reference type.<br>
>> >><br>
>> >> You can still have a handler of reference type that the exception<br>
>> >> object binds to (which is the type the user is most likely to notice<br>
>> >> since it's visibly spelled out). Also, since this diagnostic sometimes<br>
>> >> needs to print the pointer, I'm not certain it's worth the added<br>
>> >> complexity to strip in the case of references.<br>
>> >><br>
>> >> Thanks!<br>
>> >><br>
>> >> ~Aaron<br>
>> >><br>
>> >>><br>
>> >>>><br>
>> >>>> > // get here instead<br>
>> >>>> > }<br>
>> >>>> > }<br>
>> >>>> ><br>
>> >>>> > Yikes, the warning is sort of a false-positive here! (The text of<br>
>> >>>> > the<br>
>> >>>> > warning is true, but the 'throw D()' will actually be caught by the<br>
>> >>>> > second<br>
>> >>>> > handler, because A is an ambiguous base of D).<br>
>> >>>><br>
>> >>>> Oye, that is basically a false positive, and I'm not certain there's<br>
>> >>>> much I could realistically do about it either. :-(<br>
>> >>>><br>
>> >>>> Thanks!<br>
>> >>>><br>
>> >>>> ~Aaron<br>
>> >>>><br>
>> >>>> ><br>
>> >>>> > On Thu, Dec 4, 2014 at 7:23 AM, Aaron Ballman<br>
>> >>>> > <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> >>>> > wrote:<br>
>> >>>> >><br>
>> >>>> >> Ping<br>
>> >>>> >><br>
>> >>>> >> On Tue, Nov 25, 2014 at 9:59 AM, Aaron Ballman<br>
>> >>>> >> <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> >>>> >> wrote:<br>
>> >>>> >> > Ping<br>
>> >>>> >> ><br>
>> >>>> >> > On Mon, Nov 17, 2014 at 4:15 PM, Aaron Ballman<br>
>> >>>> >> > <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> >>>> >> > wrote:<br>
>> >>>> >> >> On Fri, Nov 14, 2014 at 5:36 PM, Richard Smith<br>
>> >>>> >> >> <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>><br>
>> >>>> >> >> wrote:<br>
>> >>>> >> >>> On Fri, Nov 14, 2014 at 7:55 AM, Aaron Ballman<br>
>> >>>> >> >>> <<a href="mailto:aaron@aaronballman.com">aaron@aaronballman.com</a>><br>
>> >>>> >> >>> wrote:<br>
>> >>>> >> >>>><br>
>> >>>> >> >>>> On Thu, Nov 13, 2014 at 10:06 PM, Richard Smith<br>
>> >>>> >> >>>> <<a href="mailto:richard@metafoo.co.uk">richard@metafoo.co.uk</a>><br>
>> >>>> >> >>>> wrote:<br>
>> >>>> >> >>>> > + std::list<QualType> BaseClassTypes;<br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > This will allocate memory for every node; it would be<br>
>> >>>> >> >>>> > better to<br>
>> >>>> >> >>>> > use<br>
>> >>>> >> >>>> > a<br>
>> >>>> >> >>>> > SmallVector here (and use a depth-first search rather than<br>
>> >>>> >> >>>> > a<br>
>> >>>> >> >>>> > breadth-first<br>
>> >>>> >> >>>> > one so you're only modifying one end of your list).<br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > + for (auto &CurType : BaseClassTypes) {<br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > It's a bit scary to be iterating over your container while<br>
>> >>>> >> >>>> > modifying it<br>
>> >>>> >> >>>> > (even though it's actually correct in this case).<br>
>> >>>> >> >>>> > Alternative<br>
>> >>>> >> >>>> > idiom:<br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > SmallVector<QualType, 8> BaseClassTypes;<br>
>> >>>> >> >>>> > BaseClassTypes.push_back(...);<br>
>> >>>> >> >>>> > while (!BaseClassTypes.empty()) {<br>
>> >>>> >> >>>> > QualType T = BaseClassTypes.pop_back_val();<br>
>> >>>> >> >>>> > // ... maybe push back some values.<br>
>> >>>> >> >>>> > }<br>
>> >>>> >> >>>><br>
>> >>>> >> >>>> I have a strong preference for your idiom. ;-)<br>
>> >>>> >> >>>><br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > + auto I = std::find_if(<br>
>> >>>> >> >>>> > + HandledTypes.begin(), HandledTypes.end(),<br>
>> >>>> >> >>>> ><br>
>> >>>> >> >>>> > This is still quadratic-time; maybe use a DenseMap with the<br>
>> >>>> >> >>>> > canonical<br>
>> >>>> >> >>>> > QualType plus a "was it a pointer" flag as a key?<br>
>> >>>> >> >>>><br>
>> >>>> >> >>>> I've given this a shot in my latest patch. Thank you for the<br>
>> >>>> >> >>>> feedback!<br>
>> >>>> >> >>><br>
>> >>>> >> >>><br>
>> >>>> >> >>> + unsigned IsReference : 1;<br>
>> >>>> >> >>><br>
>> >>>> >> >>> I think we don't need / want an IsReference flag. Consider:<br>
>> >>>> >> >>><br>
>> >>>> >> >>> try { throw Derived(); }<br>
>> >>>> >> >>> catch (Base) {}<br>
>> >>>> >> >>> catch (Derived &d) {}<br>
>> >>>> >> >>><br>
>> >>>> >> >>> The second catch handler is unreachable even though we have a<br>
>> >>>> >> >>> by<br>
>> >>>> >> >>> reference/by value mismatch.<br>
>> >>>> >> >><br>
>> >>>> >> >> That's a very good point. Thanks! I've added an additional test<br>
>> >>>> >> >> for<br>
>> >>>> >> >> that case.<br>
>> >>>> >> >><br>
>> >>>> >> >>><br>
>> >>>> >> >>><br>
>> >>>> >> >>> + QualType Underlying = CurType.underlying();<br>
>> >>>> >> >>> + if (auto *RD = Underlying->getAsCXXRecordDecl()) {<br>
>> >>>> >> >>> + for (const auto &B : RD->bases())<br>
>> >>>> >> >>> + BaseClassTypes.push_back(QualTypeExt(B.getType(),<br>
>> >>>> >> >>> CurType.isPointer(),<br>
>> >>>> >> >>> +<br>
>> >>>> >> >>> CurType.isReference()));<br>
>> >>>> >> >>><br>
>> >>>> >> >>> Per [except.handle]p1, you should only consider public,<br>
>> >>>> >> >>> unambiguous<br>
>> >>>> >> >>> base<br>
>> >>>> >> >>> classes here. Rather than walk the base classes yourself, you<br>
>> >>>> >> >>> could<br>
>> >>>> >> >>> use<br>
>> >>>> >> >>> CXXRecordDecl::lookupInBases to enumerate the base classes and<br>
>> >>>> >> >>> paths,<br>
>> >>>> >> >>> and<br>
>> >>>> >> >>> then check the public unambiguous ones.<br>
>> >>>> >> >><br>
>> >>>> >> >> I've made this change in the attached patch. Additionally, this<br>
>> >>>> >> >> patch<br>
>> >>>> >> >> no longer pays attention to exception declarations that are<br>
>> >>>> >> >> invalid,<br>
>> >>>> >> >> such as can be had from using auto in a catch clause.<br>
>> >>>> >> >><br>
>> >>>> >> >> Thanks!<br>
>> >>>> >> >><br>
>> >>>> >> >> ~Aaron<br>
>> >>>> ><br>
>> >>>> ><br>
>> >>><br>
>> >>><br>
><br>
><br>
</div></div></blockquote></div><br></div>