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 ~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 >> >> > >> >> >
recordDecl.patch
Description: Binary data
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