On Mon, Sep 14, 2015 at 10:21 AM Daniel Jasper <djas...@google.com> wrote:
> So, back in the day when we implemented the matchers, we decided on > actually wanting to remove all the CXX... AST nodes (there are more of > them). > Note that Richard has paddled back on this and now says the CXX... AST nodes are the right thing. > I don't know how this would work as recordDecl already exists. But I'd be > somewhat hesitant to introduce a cxxRecordDecl matcher if there is still a > chance that we want to move away from the CXX prefix. > See above. Also note that AST matchers are used massively in the wild by now and I > would be very hesitant to make a change breaking backwards compatibility. > 85 failures in the clang repositories themselves sounds scary to me. Not > saying we shouldn't do it at all. But we should be very clear on where > things should be in the long run. > Aaron has clarified that that's only 14 outside the AST matcher tests themselves. > > On Mon, Sep 14, 2015 at 7:03 PM, Aaron Ballman <aa...@aaronballman.com> > wrote: > >> On Mon, Sep 14, 2015 at 11:49 AM, Manuel Klimek <kli...@google.com> >> wrote: >> > >> > >> > On Mon, Sep 14, 2015, 8:40 AM Aaron Ballman <aa...@aaronballman.com> >> wrote: >> >> >> >> On Sat, Sep 12, 2015 at 11:06 PM, Manuel Klimek <kli...@google.com> >> wrote: >> >> > >> >> > >> >> > On Sat, Sep 12, 2015, 9:25 PM Aaron Ballman <aa...@aaronballman.com> >> >> > wrote: >> >> >> >> >> >> On Sat, Sep 12, 2015 at 8:22 AM, Manuel Klimek <kli...@google.com> >> >> >> wrote: >> >> >> > >> >> >> > >> >> >> > On Fri, Sep 11, 2015 at 10:39 PM Aaron Ballman >> >> >> > <aa...@aaronballman.com> >> >> >> > wrote: >> >> >> >> >> >> >> >> On Fri, Sep 11, 2015 at 4:30 PM, Richard Smith >> >> >> >> <rich...@metafoo.co.uk> >> >> >> >> wrote: >> >> >> >> > I don't think CXXRecordDecl is an anachronism, so much as an >> >> >> >> > implementation >> >> >> >> > detail; it makes sense to use a smaller class when in C mode, >> as >> >> >> >> > we >> >> >> >> > don't >> >> >> >> > need most of the features and complexity that CXXRecordDecl >> brings >> >> >> >> > with >> >> >> >> > it. >> >> >> >> > But... as a user of clang matchers, I don't think I'd want to >> care >> >> >> >> > about >> >> >> >> > the >> >> >> >> > difference, and it'd be more convenient if I could nest (say) a >> >> >> >> > hasMethod >> >> >> >> > matcher within a recordDecl matcher, since it's completely >> obvious >> >> >> >> > what >> >> >> >> > that >> >> >> >> > should mean. If I have a matcher that says: >> >> >> >> > >> >> >> >> > recordDecl(or(hasMethod(...), hasField(...))) >> >> >> >> > >> >> >> >> > I would expect that to work in both C and C++ (and the only >> way it >> >> >> >> > could >> >> >> >> > match in C would be on a record with the specified field, since >> >> >> >> > the >> >> >> >> > hasMethod matcher would always fail). >> >> >> >> >> >> >> >> Okay, so then it sounds like we want recordDecl to *mean* >> >> >> >> RecordDecl, >> >> >> >> but we want the traversal and narrowing matchers that currently >> take >> >> >> >> a >> >> >> >> CXXRecordDecl to instead take a RecordDecl and handle the CXX >> part >> >> >> >> transparently? This means we would not need to add a >> cxxRecordDecl() >> >> >> >> matcher, but could still access CXX-only functionality (like >> access >> >> >> >> control, base classes, etc) through recordDecl()? >> >> >> > >> >> >> > >> >> >> > I'm against that proposal. I think we have tried to make the >> matchers >> >> >> > more >> >> >> > "user friendly" in the past, and all those attempts have failed >> >> >> > miserably; >> >> >> > in the end, users will do ast-dump to see what they want to match, >> >> >> > and >> >> >> > then >> >> >> > be confused when the matchers do follow the AST 99% of the time, >> but >> >> >> > try >> >> >> > to >> >> >> > be smart 1% of the time. >> >> >> > I think given that we want to keep CXXRecordDecl, the right >> solution >> >> >> > is >> >> >> > to >> >> >> > have a cxxRecordDecl() matcher. >> >> >> >> >> >> Personally, I think this makes the most sense, at least to me. The >> >> >> recommendation I've always heard (and given) is to use -ast-dump and >> >> >> write matchers from there. (Consequently, the more I work with type >> >> >> traversal matchers, the more I wish we had -ast-dump-types to give >> >> >> even *more* information for writing matchers.) >> >> >> >> >> >> But the question still remains, what do we do with recordDecl? Right >> >> >> now, it means CXXRecordDecl instead of RecordDecl. If we change it >> to >> >> >> mean RecordDecl instead, there's a chance we'll break existing, >> >> >> reasonable code. Are we okay with that risk? If we're at least >> >> >> conceptually okay with it, I could make the change locally and see >> >> >> just how much of our own code breaks, and report back. But if that >> >> >> turns out to be problematic, do we want to deprecate recordDecl and >> >> >> replace it with structDecl as our fallback position? Or is there a >> >> >> better solution? >> >> >> >> >> >> Basically, I see a few ways to solve this (and there may be other >> ways >> >> >> I'm not thinking about yet): >> >> >> >> >> >> 1) Undocument/deprecate recordDecl, add structDecl, unionDecl, and >> >> >> cxxRecordDecl. This does not match the AST because we have no >> >> >> StructDecl or UnionDecl types. The more I think about this option, >> the >> >> >> less I like it. It's easy to implement, but seems hard to relate to >> >> >> the AST. >> >> >> 2) Make recordDecl match RecordDecl, don't touch other matchers. Add >> >> >> way to distinguish unions from structs (e.g., isUnion(), >> isStruct()), >> >> >> add cxxRecordDecl. This matches the AST most closely, but may break >> >> >> code. I think that I prefer this approach, but it depends heavily on >> >> >> what "may break code" looks like in practice. >> >> >> 3) Make recordDecl match RecordDecl, fix other matchers that >> currently >> >> >> take CXXRecordDecl to instead take RecordDecl and handle sensibly >> when >> >> >> possible. Add a way to distinguish unions from structs, add >> >> >> cxxRecordDecl. This doesn't match the AST because we will have >> >> >> matchers taking a RecordDecl when the AST would require a >> >> >> CXXRecordDecl, but is likely to break less code. >> >> > >> >> > >> >> > That sums it up. My preferences are 2, 3, 1 in that order :) >> >> >> >> I've attached a patch that implements #2, but it comes with ~85 errors >> >> from C++ matchers that use recordDecl to mean cxxRecordDecl. >> >> >> >> http://pastebin.com/bxkRcqBV >> >> >> >> If this is an acceptable failure rate, I can also update the failing >> >> matchers to use cxxRecordDecl instead of recordDecl where applicable. >> >> Doing some spot-checking of the failing code, the failures are ones we >> >> anticipated, such as: >> >> >> >> constructorDecl(ofClass(recordDecl( >> >> hasDeclaration(recordDecl(hasMethod(hasName("begin")), >> >> hasMethod(hasName("end")))) >> >> etc >> > >> > >> > +Daniel for another opinion. I think this is fine, but I'd prefer not >> to >> > end up in a meme :) >> >> FWIW, the vast majority of the errors are in ASTMatchersTests. There >> were only a few in actual real-world uses (71 in tests, 14 in real >> code). >> >> ~Aaron >> >> > >> >> ~Aaron >> >> >> >> > >> >> >> >> >> >> ~Aaron >> >> >> >> >> >> >> >> >> > Richard: if CXXRecordDecl was really an implementation detail, it >> >> >> > would >> >> >> > be >> >> >> > hidden behind a RecordDecl class, as an implementation detail. The >> >> >> > reasons >> >> >> > why we don't want it to be an implementation detail in the code >> >> >> > (performance, data structure size) don't matter - in the end, >> it's in >> >> >> > the >> >> >> > AST API. >> >> >> > >> >> >> >> >> >> >> >> >> >> >> >> ~Aaron >> >> >> >> >> >> >> >> > >> >> >> >> > On Fri, Sep 11, 2015 at 6:30 AM, Manuel Klimek < >> kli...@google.com> >> >> >> >> > wrote: >> >> >> >> >> >> >> >> >> >> Richard! We need an informed opinion :D >> >> >> >> >> >> >> >> >> >> On Fri, Sep 11, 2015 at 3:07 PM Aaron Ballman >> >> >> >> >> <aa...@aaronballman.com> >> >> >> >> >> wrote: >> >> >> >> >>> >> >> >> >> >>> Ping? >> >> >> >> >>> >> >> >> >> >>> On Tue, Sep 8, 2015 at 9:26 AM, Manuel Klimek >> >> >> >> >>> <kli...@google.com> >> >> >> >> >>> wrote: >> >> >> >> >>> > On Tue, Sep 8, 2015 at 3:23 PM Aaron Ballman >> >> >> >> >>> > <aa...@aaronballman.com> >> >> >> >> >>> > wrote: >> >> >> >> >>> >> >> >> >> >> >>> >> On Tue, Sep 8, 2015 at 9:18 AM, Manuel Klimek >> >> >> >> >>> >> <kli...@google.com> >> >> >> >> >>> >> wrote: >> >> >> >> >>> >> > On Tue, Sep 8, 2015 at 2:23 PM Aaron Ballman >> >> >> >> >>> >> > <aa...@aaronballman.com> >> >> >> >> >>> >> > wrote: >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> On Tue, Sep 8, 2015 at 5:40 AM, Manuel Klimek >> >> >> >> >>> >> >> <kli...@google.com> >> >> >> >> >>> >> >> wrote: >> >> >> >> >>> >> >> > Yea, we had that discussion a few times, and I can >> never >> >> >> >> >>> >> >> > remember >> >> >> >> >>> >> >> > why >> >> >> >> >>> >> >> > we >> >> >> >> >>> >> >> > ended up in the state we're in. >> >> >> >> >>> >> >> > We definitely had a time where we switched to just >> using >> >> >> >> >>> >> >> > the >> >> >> >> >>> >> >> > exact >> >> >> >> >>> >> >> > same >> >> >> >> >>> >> >> > name >> >> >> >> >>> >> >> > as the node's class name for the matchers. >> >> >> >> >>> >> >> > I *think* we didn't do it for cxxRecordDecl, because >> >> >> >> >>> >> >> > Richard >> >> >> >> >>> >> >> > said >> >> >> >> >>> >> >> > that's >> >> >> >> >>> >> >> > a >> >> >> >> >>> >> >> > relic we should get rid of anyway, but I'm not sure. >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> FWIW, I think the state we're in is the worst of all >> >> >> >> >>> >> >> worlds. >> >> >> >> >>> >> >> It's >> >> >> >> >>> >> >> not >> >> >> >> >>> >> >> intuitive that recordDecl() doesn't match a struct in C >> >> >> >> >>> >> >> mode, >> >> >> >> >>> >> >> and >> >> >> >> >>> >> >> as >> >> >> >> >>> >> >> it stands, there is no way to match a struct or union >> >> >> >> >>> >> >> declaration >> >> >> >> >>> >> >> in C >> >> >> >> >>> >> >> at all. >> >> >> >> >>> >> > >> >> >> >> >>> >> > >> >> >> >> >>> >> > Agreed. Best intentions. Worst possible outcome. That's >> >> >> >> >>> >> > software >> >> >> >> >>> >> > development >> >> >> >> >>> >> > :) >> >> >> >> >>> >> > >> >> >> >> >>> >> >> > >> >> >> >> >>> >> >> > On Fri, Sep 4, 2015 at 8:32 PM Aaron Ballman >> >> >> >> >>> >> >> > <aa...@aaronballman.com> >> >> >> >> >>> >> >> > wrote: >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> It turns out that the recordDecl() AST matcher >> doesn't >> >> >> >> >>> >> >> >> match >> >> >> >> >>> >> >> >> RecordDecl objects; instead, it matches >> CXXRecordDecl >> >> >> >> >>> >> >> >> objects. >> >> >> >> >>> >> >> >> This >> >> >> >> >>> >> >> >> is... unfortunate... as it makes writing AST >> matchers >> >> >> >> >>> >> >> >> more >> >> >> >> >>> >> >> >> complicated >> >> >> >> >>> >> >> >> because of having to translate between >> >> >> >> >>> >> >> >> recordDecl()/CXXRecordDecl. >> >> >> >> >>> >> >> >> It >> >> >> >> >>> >> >> >> also makes it impossible to match a struct or union >> >> >> >> >>> >> >> >> declaration >> >> >> >> >>> >> >> >> in C >> >> >> >> >>> >> >> >> or ObjC. However, given how prevalent recordDecl()'s >> >> >> >> >>> >> >> >> use >> >> >> >> >>> >> >> >> is >> >> >> >> >>> >> >> >> in >> >> >> >> >>> >> >> >> the >> >> >> >> >>> >> >> >> wild (I'm guessing), changing it at this point >> would be >> >> >> >> >>> >> >> >> a >> >> >> >> >>> >> >> >> Bad >> >> >> >> >>> >> >> >> Thing. >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> For people trying to write AST matchers for >> languages >> >> >> >> >>> >> >> >> like >> >> >> >> >>> >> >> >> C >> >> >> >> >>> >> >> >> or >> >> >> >> >>> >> >> >> ObjC, >> >> >> >> >>> >> >> >> I would like to propose adding: >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> structDecl() >> >> >> >> >>> >> >> >> unionDecl() >> >> >> >> >>> >> >> >> tagDecl() >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> These will match nicely with the existing enumDecl() >> >> >> >> >>> >> >> >> AST >> >> >> >> >>> >> >> >> matcher. >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> Additionally, I would like to add cxxRecordDecl() to >> >> >> >> >>> >> >> >> match >> >> >> >> >>> >> >> >> CXXRecordDecl objects. While it duplicates the >> >> >> >> >>> >> >> >> functionality >> >> >> >> >>> >> >> >> exposed >> >> >> >> >>> >> >> >> by recordDecl(), it more clearly matches the >> intention >> >> >> >> >>> >> >> >> of >> >> >> >> >>> >> >> >> which >> >> >> >> >>> >> >> >> AST >> >> >> >> >>> >> >> >> node it corresponds to. >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> Finally, I would like to undocument recordDecl() and >> >> >> >> >>> >> >> >> change >> >> >> >> >>> >> >> >> our >> >> >> >> >>> >> >> >> existing documentation and AST matcher uses to use >> >> >> >> >>> >> >> >> cxxRecordDecl/structDecl() instead. Maybe someday we >> >> >> >> >>> >> >> >> can >> >> >> >> >>> >> >> >> deprecate >> >> >> >> >>> >> >> >> recordDecl() more officially. >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> I'm open to other ideas if there are better ways to >> >> >> >> >>> >> >> >> move >> >> >> >> >>> >> >> >> forward. If >> >> >> >> >>> >> >> >> you think changing the meaning of recordDecl() is >> >> >> >> >>> >> >> >> acceptable, >> >> >> >> >>> >> >> >> I >> >> >> >> >>> >> >> >> can >> >> >> >> >>> >> >> >> also go that route (though I would still propose >> adding >> >> >> >> >>> >> >> >> unionDecl() >> >> >> >> >>> >> >> >> and cxxRecordDecl() in that case). >> >> >> >> >>> >> >> > >> >> >> >> >>> >> >> > >> >> >> >> >>> >> >> > I think changing recordDecl is acceptable. I believe >> >> >> >> >>> >> >> > very >> >> >> >> >>> >> >> > few >> >> >> >> >>> >> >> > tools >> >> >> >> >>> >> >> > will >> >> >> >> >>> >> >> > actually start doing wrong things because of it. I'd >> >> >> >> >>> >> >> > like >> >> >> >> >>> >> >> > more >> >> >> >> >>> >> >> > opinions >> >> >> >> >>> >> >> > first, though :) >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> I was giving this more thought over the long weekend, >> and >> >> >> >> >>> >> >> I >> >> >> >> >>> >> >> think >> >> >> >> >>> >> >> you >> >> >> >> >>> >> >> may be right. I think changing recordDecl() to mean >> >> >> >> >>> >> >> RecordDecl >> >> >> >> >>> >> >> will >> >> >> >> >>> >> >> fix more code than it breaks, so long as we take a >> >> >> >> >>> >> >> holistic >> >> >> >> >>> >> >> approach >> >> >> >> >>> >> >> to the change and see which narrowing and traversal >> >> >> >> >>> >> >> matchers >> >> >> >> >>> >> >> we >> >> >> >> >>> >> >> need >> >> >> >> >>> >> >> to fix up at the same time. When I tried to think of >> AST >> >> >> >> >>> >> >> matchers >> >> >> >> >>> >> >> that >> >> >> >> >>> >> >> mean CXXRecordDecl but *not* RecordDecl, they were >> >> >> >> >>> >> >> horribly >> >> >> >> >>> >> >> contrived >> >> >> >> >>> >> >> because you usually are matching on additional >> selection >> >> >> >> >>> >> >> criteria >> >> >> >> >>> >> >> that >> >> >> >> >>> >> >> is specific to C++ (such as hasMethod() or >> >> >> >> >>> >> >> isDerivedFrom()) >> >> >> >> >>> >> >> which >> >> >> >> >>> >> >> would cause the match to continue to fail, as expected. >> >> >> >> >>> >> >> Code >> >> >> >> >>> >> >> that >> >> >> >> >>> >> >> uses >> >> >> >> >>> >> >> recordDecl() to mean RecordDecl will suddenly start to >> >> >> >> >>> >> >> match >> >> >> >> >>> >> >> in >> >> >> >> >>> >> >> more >> >> >> >> >>> >> >> cases, but that's likely to be a bug fix more than a >> >> >> >> >>> >> >> breaking >> >> >> >> >>> >> >> change. >> >> >> >> >>> >> >> To the best of my understanding, the only breaking >> cases >> >> >> >> >>> >> >> would >> >> >> >> >>> >> >> be >> >> >> >> >>> >> >> where you wrote recordDecl(), meant CXXRecordDecl, had >> no >> >> >> >> >>> >> >> further >> >> >> >> >>> >> >> narrowing or traversal matchers, and were compiling in >> C >> >> >> >> >>> >> >> mode; >> >> >> >> >>> >> >> with >> >> >> >> >>> >> >> the result being additional unexpected matches. >> >> >> >> >>> >> > >> >> >> >> >>> >> > >> >> >> >> >>> >> > Ah, there's one thing that can break: the compile can >> >> >> >> >>> >> > break: >> >> >> >> >>> >> > recordDecl(hasMethod(...)) will *not* compile (it'll >> work >> >> >> >> >>> >> > in >> >> >> >> >>> >> > the >> >> >> >> >>> >> > dynamic >> >> >> >> >>> >> > matchers and fail as you suggest, but the in-C++ DSL >> does >> >> >> >> >>> >> > more >> >> >> >> >>> >> > static >> >> >> >> >>> >> > type >> >> >> >> >>> >> > checking). >> >> >> >> >>> >> > I don't think that's super bad though. >> >> >> >> >>> >> > >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> So perhaps it would make sense to: >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> 1) Make recordDecl() mean RecordDecl >> >> >> >> >>> >> >> 2) Do a comprehensive review of matchers that take a >> >> >> >> >>> >> >> CXXRecordDecl >> >> >> >> >>> >> >> and >> >> >> >> >>> >> >> see if they should instead take a RecordDecl >> >> >> >> >>> >> >> 3) Add unionDecl() as a node matcher (or should we add >> >> >> >> >>> >> >> isUnion() >> >> >> >> >>> >> >> and >> >> >> >> >>> >> >> isStruct() as narrowing matchers?) >> >> >> >> >>> >> >> 4) Add tagDecl() as a node matcher, but not add >> >> >> >> >>> >> >> cxxRecordDecl() >> >> >> >> >>> >> > >> >> >> >> >>> >> > >> >> >> >> >>> >> > Why not add cxxRecordDecl()? I think we need it if we >> want >> >> >> >> >>> >> > narrowing >> >> >> >> >>> >> > matchers on CXXRecordDecl? >> >> >> >> >>> >> >> >> >> >> >>> >> If Richard thinks CXXRecordDecl is an anachronism, I >> figured >> >> >> >> >>> >> we >> >> >> >> >>> >> didn't >> >> >> >> >>> >> want to expose it. Instead, we could make hasMethod (et >> al) >> >> >> >> >>> >> accept >> >> >> >> >>> >> a >> >> >> >> >>> >> RecordDecl and do the type checking for the caller. Then >> >> >> >> >>> >> recordDecl(hasMethod(...)) continues to compile and work, >> and >> >> >> >> >>> >> when >> >> >> >> >>> >> hasMethod is given a RecordDecl instead of a >> CXXRecordDecl, >> >> >> >> >>> >> it >> >> >> >> >>> >> simply >> >> >> >> >>> >> matches nothing. But you bring up a good point about the >> C++ >> >> >> >> >>> >> DSL >> >> >> >> >>> >> being >> >> >> >> >>> >> a problem still, I hadn't considered that. >> >> >> >> >>> > >> >> >> >> >>> > >> >> >> >> >>> > First I want Richard to confirm that. I have a very bad >> >> >> >> >>> > memory, >> >> >> >> >>> > so I >> >> >> >> >>> > might >> >> >> >> >>> > as well misremember :) >> >> >> >> >>> > >> >> >> >> >>> >> >> >> >> >> >>> >> >> >> >> >> >>> >> ~Aaron >> >> >> >> >>> >> >> >> >> >> >>> >> > >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> ~Aaron >> >> >> >> >>> >> >> >> >> >> >> >>> >> >> > >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> Thanks! >> >> >> >> >>> >> >> >> >> >> >> >> >>> >> >> >> ~Aaron >> >> >> >> > >> >> >> >> > >> > >
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