r280728 - Modules: Fix an assertion in DeclContext::buildLookup.
Manman Ren via cfe-commits
cfe-commits at lists.llvm.org
Fri Sep 9 12:07:28 PDT 2016
On Fri, Sep 9, 2016 at 11:33 AM, Richard Smith <richard at metafoo.co.uk>
wrote:
> On Fri, Sep 9, 2016 at 11:29 AM, Manman Ren via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> On Wed, Sep 7, 2016 at 4:44 PM, Richard Smith <richard at metafoo.co.uk>
>> wrote:
>>
>>> On Wed, Sep 7, 2016 at 12:45 PM, Manman Ren <manman.ren at gmail.com>
>>> wrote:
>>>
>>>> On Tue, Sep 6, 2016 at 6:54 PM, Richard Smith <richard at metafoo.co.uk>
>>>> wrote:
>>>>
>>>>> On Tue, Sep 6, 2016 at 11:16 AM, Manman Ren via cfe-commits <
>>>>> cfe-commits at lists.llvm.org> wrote:
>>>>>
>>>>>> Author: mren
>>>>>> Date: Tue Sep 6 13:16:54 2016
>>>>>> New Revision: 280728
>>>>>>
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=280728&view=rev
>>>>>> Log:
>>>>>> Modules: Fix an assertion in DeclContext::buildLookup.
>>>>>>
>>>>>> When calling getMostRecentDecl, we can pull in more definitions from
>>>>>> a module. We call getPrimaryContext afterwards to make sure that
>>>>>> we buildLookup on a primary context.
>>>>>>
>>>>>> rdar://27926200
>>>>>>
>>>>>> Added:
>>>>>> cfe/trunk/test/Modules/Inputs/lookup-assert/
>>>>>> cfe/trunk/test/Modules/Inputs/lookup-assert/Base.h
>>>>>> cfe/trunk/test/Modules/Inputs/lookup-assert/Derive.h
>>>>>> cfe/trunk/test/Modules/Inputs/lookup-assert/H3.h
>>>>>> cfe/trunk/test/Modules/Inputs/lookup-assert/module.map
>>>>>> cfe/trunk/test/Modules/lookup-assert.m
>>>>>> Modified:
>>>>>> cfe/trunk/lib/AST/DeclBase.cpp
>>>>>>
>>>>>> Modified: cfe/trunk/lib/AST/DeclBase.cpp
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/DeclBa
>>>>>> se.cpp?rev=280728&r1=280727&r2=280728&view=diff
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/lib/AST/DeclBase.cpp (original)
>>>>>> +++ cfe/trunk/lib/AST/DeclBase.cpp Tue Sep 6 13:16:54 2016
>>>>>> @@ -1411,10 +1411,6 @@ DeclContext::lookup(DeclarationName Name
>>>>>> assert(DeclKind != Decl::LinkageSpec &&
>>>>>> "Should not perform lookups into linkage specs!");
>>>>>>
>>>>>> - const DeclContext *PrimaryContext = getPrimaryContext();
>>>>>> - if (PrimaryContext != this)
>>>>>> - return PrimaryContext->lookup(Name);
>>>>>> -
>>>>>> // If we have an external source, ensure that any later
>>>>>> redeclarations of this
>>>>>> // context have been loaded, since they may add names to the
>>>>>> result of this
>>>>>> // lookup (or add external visible storage).
>>>>>> @@ -1422,6 +1418,12 @@ DeclContext::lookup(DeclarationName Name
>>>>>> if (Source)
>>>>>> (void)cast<Decl>(this)->getMostRecentDecl();
>>>>>>
>>>>>> + // getMostRecentDecl can change the result of getPrimaryContext.
>>>>>> Call
>>>>>> + // getPrimaryContext afterwards.
>>>>>> + const DeclContext *PrimaryContext = getPrimaryContext();
>>>>>> + if (PrimaryContext != this)
>>>>>> + return PrimaryContext->lookup(Name);
>>>>>>
>>>>>
>>>>> This seems like a bug in getPrimaryContext() -- if there is a
>>>>> not-yet-loaded definition of the DeclContext, getPrimaryContext() should
>>>>> return that instead of returning a non-defining declaration. Why is
>>>>> ObjCInterfaceDecl::hasDefinition (indirectly called by
>>>>> getPrimaryContext) not loading the definition in this case?
>>>>>
>>>>
>>>> In the testing case, we have a definition of the ObjC interface from
>>>> textually including a header file, but the definition is also in a module.
>>>> getPrimaryContext for ObjCInterface currently does not pull from the
>>>> external source.
>>>>
>>>
>>> As far as I can see, it does. For ObjCInterface, getPrimaryContext calls
>>> ObjCInterface::getDefinition:
>>>
>>> ObjCInterfaceDecl *getDefinition() {
>>> return hasDefinition()? Data.getPointer()->Definition : nullptr;
>>> }
>>>
>>> hasDefinition() pulls from the external source to find a definition, if
>>> it believes the definition is out of date:
>>>
>>> bool hasDefinition() const {
>>> // If the name of this class is out-of-date, bring it up-to-date,
>>> which
>>> // might bring in a definition.
>>> // Note: a null value indicates that we don't have a definition and
>>> that
>>> // modules are enabled.
>>> if (!Data.getOpaqueValue())
>>> getMostRecentDecl();
>>>
>>> return Data.getPointer();
>>> }
>>>
>> --> You are right, this is the backtrace when calling getPrimaryContext.
>> * frame #0: 0x0000000102e6c1b0 clang`clang::ObjCInterfaceDecl
>> ::hasDefinition(this=0x000000010f079a38) const + 16 at DeclObjC.h:1445
>> frame #1: 0x0000000105d09009 clang`clang::ObjCInterfaceDecl
>> ::getDefinition(this=0x000000010f079a38) + 25 at DeclObjC.h:1455
>> frame #2: 0x0000000105d08b2b clang`clang::DeclContext::getP
>> rimaryContext(this=0x000000010f079a60) + 171 at DeclBase.cpp:1013
>> frame #3: 0x0000000105d08a75 clang`clang::DeclContext::getP
>> rimaryContext(this=0x000000010f079a60) const + 21 at DeclBase.h:1360
>> frame #4: 0x0000000105d0cda4 clang`clang::DeclContext::lookup(this=0x000000010f079a60,
>> Name=(Ptr = 4547240953)) const + 164 at DeclBase.cpp:1416
>> frame #5: 0x0000000105d30804 clang`clang::ObjCContainerDecl
>> ::getMethod(this=0x000000010f079a38, Sel=(InfoPtr = 4547240953),
>> isInstance=true, AllowHidden=false) const + 212 at DeclObjC.cpp:86
>> frame #6: 0x0000000105d347bd clang`clang::ObjCInterfaceDecl
>> ::lookupMethod(this=0x000000010f079c88, Sel=(InfoPtr = 4547240953),
>> isInstance=true, shallowCategoryLookup=false, followSuper=true,
>> C=0x0000000000000000) const + 221 at DeclObjC.cpp:671
>> frame #7: 0x0000000104d1ffae clang`clang::Sema::ActOnMethod
>> Declaration(this=0x000000010f073a00, S=0x000000010e716780, MethodLoc=(ID
>> = 83), EndLoc=(ID = 96), MethodType=minus, ReturnQT=0x00007fff5fbf98c0,
>> ReturnType=(Ptr = 0x000000010f09c020), SelectorLocs=ArrayRef<clang::SourceLocation>
>> @ 0x00007fff5fbf9368, Sel=(InfoPtr = 4547240953),
>> ArgInfo=0x0000000000000000, CParamInfo=0x00007fff5fbfa318, CNumArgs=0,
>> AttrList=0x0000000000000000, MethodDeclKind=objc_not_keyword,
>> isVariadic=false, MethodDefinition=true) + 3342 at SemaDeclObjC.cpp:4414
>>
>> In the testing case
>> +#include "Derive.h"
>> +#import <H3.h>
>> we textually include Base.h from Derive.h. When calling
>> getPrimaryContext() -> hasDefinition() above, we already have a definition,
>> so we will not call getMostRecentDecl.
>>
>> We then call getMostRecentDecl from DeclContext::lookup, and will
>> deserialize a definition from module X that includes H3.h (which includes
>> Base.h).
>>
>> To correctly fix this issue, it sounds like we should do sufficient
>> deserialization in getPrimaryContext: to pull from the external source even
>> though we have a definition already.
>>
>
> Hmm. So the value returned by `ObjCInterfaceDecl::getDefinition` changes
> from one definition to another?
>
Yes, currently.
> We go to lengths to avoid this for other kinds of DeclContext because
> changes to which declaration is the (canonical) definition break AST
> invariants.
>
I just looked at how C++ handles this. I think we can make ObjectiveC do
the same thing (i.e. the logic in ReadCXXRecordDefinition and
MergeDefinitionData), so the definition can be invariant once we select it.
I will revert this commit for now.
Thanks for all the help!
Manman
> Is this really OK for the Objective-C case? I'd be a little surprised if
> this doesn't lead to more problems down the line.
>
> So, getPrimaryContext() should always pull from the external source when
>>> building with modules, unless we already have a primary context. In either
>>> case, the context returned by getPrimaryContext() should never change -- we
>>> should do sufficient deserialization for it to return the right answer.
>>>
>>>
>>>> Since getPrimaryContext does not guarantee to pull from the external
>>>> source, I thought that is why we call getMostRecentDecl in
>>>> DeclContext::lookup.
>>>>
>>>
>>> That's present to solve a different problem, where we can merge together
>>> multiple definitions of the same entity, and where later definitions can
>>> provide additional lookup results. This happens in C++ due to lazy
>>> declarations of implicit special member functions, and should never result
>>> in the primary context changing.
>>>
>>
>> Thanks for the info! I apparently misunderstood why getMostRecentDecl is
>> there.
>>
>> Manman
>>
>>
>>>
>>>
>>>> Are you suggesting to pull from external source in getPrimaryContext?
>>>>
>>>> Cheers,
>>>> Manman
>>>>
>>>>
>>>>
>>>>>
>>>>>> +
>>>>>> if (hasExternalVisibleStorage()) {
>>>>>> assert(Source && "external visible storage but no external
>>>>>> source?");
>>>>>>
>>>>>>
>>>>>> Added: cfe/trunk/test/Modules/Inputs/lookup-assert/Base.h
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/I
>>>>>> nputs/lookup-assert/Base.h?rev=280728&view=auto
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/test/Modules/Inputs/lookup-assert/Base.h (added)
>>>>>> +++ cfe/trunk/test/Modules/Inputs/lookup-assert/Base.h Tue Sep 6
>>>>>> 13:16:54 2016
>>>>>> @@ -0,0 +1,4 @@
>>>>>> + at interface BaseInterface
>>>>>> +- (void) test;
>>>>>> + at end
>>>>>> +
>>>>>>
>>>>>> Added: cfe/trunk/test/Modules/Inputs/lookup-assert/Derive.h
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/I
>>>>>> nputs/lookup-assert/Derive.h?rev=280728&view=auto
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/test/Modules/Inputs/lookup-assert/Derive.h (added)
>>>>>> +++ cfe/trunk/test/Modules/Inputs/lookup-assert/Derive.h Tue Sep 6
>>>>>> 13:16:54 2016
>>>>>> @@ -0,0 +1,3 @@
>>>>>> +#include "Base.h"
>>>>>> + at interface DerivedInterface : BaseInterface
>>>>>> + at end
>>>>>>
>>>>>> Added: cfe/trunk/test/Modules/Inputs/lookup-assert/H3.h
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/I
>>>>>> nputs/lookup-assert/H3.h?rev=280728&view=auto
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/test/Modules/Inputs/lookup-assert/H3.h (added)
>>>>>> +++ cfe/trunk/test/Modules/Inputs/lookup-assert/H3.h Tue Sep 6
>>>>>> 13:16:54 2016
>>>>>> @@ -0,0 +1 @@
>>>>>> +#include "Base.h"
>>>>>>
>>>>>> Added: cfe/trunk/test/Modules/Inputs/lookup-assert/module.map
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/I
>>>>>> nputs/lookup-assert/module.map?rev=280728&view=auto
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/test/Modules/Inputs/lookup-assert/module.map (added)
>>>>>> +++ cfe/trunk/test/Modules/Inputs/lookup-assert/module.map Tue Sep
>>>>>> 6 13:16:54 2016
>>>>>> @@ -0,0 +1,4 @@
>>>>>> +module X {
>>>>>> + header "H3.h"
>>>>>> + export *
>>>>>> +}
>>>>>>
>>>>>> Added: cfe/trunk/test/Modules/lookup-assert.m
>>>>>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/l
>>>>>> ookup-assert.m?rev=280728&view=auto
>>>>>> ============================================================
>>>>>> ==================
>>>>>> --- cfe/trunk/test/Modules/lookup-assert.m (added)
>>>>>> +++ cfe/trunk/test/Modules/lookup-assert.m Tue Sep 6 13:16:54 2016
>>>>>> @@ -0,0 +1,10 @@
>>>>>> +// RUN: rm -rf %t
>>>>>> +// RUN: %clang_cc1 -fmodules-cache-path=%t -fmodules
>>>>>> -fimplicit-module-maps -I %S/Inputs/lookup-assert %s -verify
>>>>>> +// expected-no-diagnostics
>>>>>> +
>>>>>> +#include "Derive.h"
>>>>>> +#import <H3.h>
>>>>>> + at implementation DerivedInterface
>>>>>> +- (void)test {
>>>>>> +}
>>>>>> + at end
>>>>>>
>>>>>>
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>>>>>> cfe-commits at lists.llvm.org
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>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
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