[cfe-dev] stable layout bug for imported record decls.
Lang Hames via cfe-dev
cfe-dev at lists.llvm.org
Tue Aug 14 17:52:20 PDT 2018
Hi Gábor, Richard,
Hi Richard, maybe my understanding is not correct, but I believe the
> situation is somewhat twisted and reversed...
Is this relationship recursive? (Should it be?) I.e. When ClangASTSource
uses ASTImporter to minimally import a Decl, should that Decl have another
ExternalASTSource attached (possibly the original ClangASTSource) to
complete the minimally imported Decl on demand?
-- Lang.
On Tue, Aug 14, 2018 at 6:49 AM Gábor Márton <martongabesz at gmail.com> wrote:
> > It might be interesting to consider how this is addressed by the
> ExternalASTSource interface. There, we have separate "import the lexical
> contents of this AST node (including populating the lexical declarations
> list with all members, in the right order)", "import the lookup results for
> this name in this context (and cache them but don't add them to the list of
> lexical members)" and "import this specific declaration member (but don't
> add it to the list of lexical members)" queries. One could imagine doing
> something similar for the AST importer: when you're performing a minimal
> import but you want to import a method declaration, don't insert it into
> the list of lexical members of the enclosing record. Instead, defer doing
> that until a complete type is required (at that point, you'd need to import
> all the relevant members anyway, including the base classes and virtual
> functions in the right order).
>
> Hi Richard, maybe my understanding is not correct, but I believe the
> situation is somewhat twisted and reversed.
> Seems like LLDB already exercises the ExternalASTSource interface. The
> purpose of using it is exactly to load the external lexical contents
> of an AST node (as you suggested). However, the load is implemented by
> the means of the ASTImporter (in minimal mode). Consider the attached
> function call trace:
> When the user instructs LLDB to evaluate an expression then LLDB
> exercises the parser `clang::ParseAST`, which in turn does a lookup
> `clang::DeclContext::lookup`. During the lookup,
> `lldb_private::ClangASTSource::FindExternalVisibleDeclsByName` is
> called (this function overloads
> `ExternalASTSource::FindExternalVisibleDeclsByName`).
> And finally, through `lldb_private::ClangASTImporter::CopyType` we end
> up in `clang::ASTImporter::Import`.
>
> Gabor
>
> ```
> #4 0x00007ffff41a72ed in clang::ASTNodeImporter::ImportDeclParts
> (this=this at entry=0x7fffffff8be0, D=D at entry=0x632038,
> DC=@0x7fffffff8ac8: 0x0,
> LexicalDC=@0x7fffffff8ad0: 0x0, Name=..., ToD=@0x7fffffff8ad8: 0x0,
> Loc=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/ASTImporter.cpp:1062
> #5 0x00007ffff41a8d55 in clang::ASTNodeImporter::VisitRecordDecl
> (this=0x7fffffff8be0, D=0x632038)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/ASTImporter.cpp:2126
> #6 0x00007ffff419377b in clang::ASTImporter::Import (this=0x70cc90,
> FromD=0x632038)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/ASTImporter.cpp:7054
> #7 0x00007ffff41939f7 in clang::ASTNodeImporter::VisitRecordType
> (this=0x7fffffff8c40, T=<optimized out>)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/ASTImporter.cpp:851
> #8 0x00007ffff4196f65 in clang::TypeVisitor<clang::ASTNodeImporter,
> clang::QualType>::Visit (this=this at entry=0x7fffffff8c40, T=<optimized
> out>)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/include/clang/AST/TypeNodes.def:92
> #9 0x00007ffff4197187 in clang::ASTImporter::Import (this=0x70cc90,
> FromT=FromT at entry=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/ASTImporter.cpp:6983
> #10 0x00007ffff7351c92 in lldb_private::ClangASTImporter::CopyType
> (this=<optimized out>, dst_ast=<optimized out>, src_ast=<optimized
> out>, type=type at entry=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Symbol/ClangASTImporter.cpp:61
> #11 0x00007ffff74bdb95 in
> lldb_private::ClangASTSource::GuardedCopyType
> (this=this at entry=0x611e20, src_type=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp:2040
> #12 0x00007ffff74e9ffe in
> lldb_private::ClangExpressionDeclMap::GetVariableValue
> (this=this at entry=0x611e20, var=std::shared_ptr (count 6, weak 1)
> 0x7fffe80020f0,
> var_location=..., user_type=user_type at entry=0x7fffffff8fc0,
> parser_type=parser_type at entry=0x7fffffff8fe0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp:1627
> #13 0x00007ffff74ea3a7 in
> lldb_private::ClangExpressionDeclMap::AddOneVariable
> (this=this at entry=0x611e20, context=...,
> var=std::shared_ptr (count 6, weak 1) 0x7fffe80020f0, valobj=...,
> current_id=current_id at entry=2)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp:1679
> #14 0x00007ffff74ec50b in
> lldb_private::ClangExpressionDeclMap::FindExternalVisibleDecls
> (this=this at entry=0x611e20, context=..., module_sp=
> std::shared_ptr (empty) 0x0, namespace_decl=...,
> current_id=current_id at entry=2)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp:1240
> #15 0x00007ffff74ef4ce in
> lldb_private::ClangExpressionDeclMap::FindExternalVisibleDecls
> (this=0x611e20, context=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionDeclMap.cpp:843
> #16 0x00007ffff74c71cc in
> lldb_private::ClangASTSource::FindExternalVisibleDeclsByName
> (this=0x611e20, decl_ctx=0x71d8b8, clang_decl_name=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangASTSource.cpp:261
> #17 0x00007ffff421d92d in clang::DeclContext::lookup
> (this=this at entry=0x71d8b8, Name=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/AST/DeclBase.cpp:1577
> #18 0x00007ffff4d4bb42 in LookupDirect (S=..., R=..., DC=DC at entry
> =0x71d8b8)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Sema/SemaLookup.cpp:843
> #19 0x00007ffff4d52f50 in CppNamespaceLookup (S=..., R=...,
> NS=NS at entry=0x71d8b8, UDirs=..., Context=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Sema/SemaLookup.cpp:942
> #20 0x00007ffff4d53925 in clang::Sema::CppLookupName
> (this=this at entry=0x7245b0, R=..., S=0x72cad0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Sema/SemaLookup.cpp:1322
> #21 0x00007ffff4d53c8a in clang::Sema::LookupName (this=0x7245b0,
> R=..., S=0x7314f0, AllowBuiltinCreation=<optimized out>)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Sema/SemaLookup.cpp:1827
> #22 0x00007ffff4b6b945 in clang::Sema::ClassifyName (this=0x7245b0,
> S=0x7314f0, SS=..., Name=@0x7fffffffa3a8: 0x750dc8, NameLoc=...,
> NameLoc at entry=...,
> NextToken=..., IsAddressOfOperand=false,
> CCC=std::unique_ptr<clang::CorrectionCandidateCallback> containing
> 0x63c250)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Sema/SemaDecl.cpp:868
> #23 0x00007ffff52c6a9f in clang::Parser::TryAnnotateName
> (this=this at entry=0x728c60,
> IsAddressOfOperand=IsAddressOfOperand at entry=false,
> CCC=std::unique_ptr<clang::CorrectionCandidateCallback> containing
> 0x0) at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:1531
> #24 0x00007ffff52aa56b in
> clang::Parser::ParseStatementOrDeclarationAfterAttributes
> (this=this at entry=0x728c60, Stmts=...,
> Allowed=Allowed at entry=clang::Parser::ACK_Any,
> TrailingElseLoc=<optimized out>, Attrs=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseStmt.cpp:189
> #25 0x00007ffff52aa843 in clang::Parser::ParseStatementOrDeclaration
> (this=this at entry=0x728c60, Stmts=...,
> Allowed=Allowed at entry=clang::Parser::ACK_Any,
> TrailingElseLoc=TrailingElseLoc at entry=0x0) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseStmt.cpp:111
> #26 0x00007ffff52ae577 in clang::Parser::ParseCompoundStatementBody
> (this=this at entry=0x728c60, isStmtExpr=isStmtExpr at entry=false)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseStmt.cpp:1003
> #27 0x00007ffff52b0a49 in clang::Parser::ParseFunctionStatementBody
> (this=this at entry=0x728c60, Decl=Decl at entry=0x72dbd0, BodyScope=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseStmt.cpp:1972
> #28 0x00007ffff52cc6e0 in clang::Parser::ParseFunctionDefinition
> (this=this at entry=0x728c60, D=..., TemplateInfo=...,
> LateParsedAttrs=LateParsedAttrs at entry=0x7fffffffabe0) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:1248
> #29 0x00007ffff524aa56 in clang::Parser::ParseDeclGroup
> (this=this at entry=0x728c60, DS=...,
> Context=Context at entry=clang::DeclaratorContext::FileContext,
> DeclEnd=DeclEnd at entry=0x0, FRI=FRI at entry=0x0) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseDecl.cpp:1968
> #30 0x00007ffff52c7f90 in
> clang::Parser::ParseDeclOrFunctionDefInternal
> (this=this at entry=0x728c60, attrs=..., DS=...,
> AS=AS at entry=clang::AS_none)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:1012
> #31 0x00007ffff52c8761 in
> clang::Parser::ParseDeclarationOrFunctionDefinition (this=0x728c60,
> attrs=..., AS=clang::AS_none, DS=0x0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:1028
> #32 0x00007ffff52c87bf in
> clang::Parser::ParseDeclarationOrFunctionDefinition (this=<optimized
> out>, attrs=..., DS=<optimized out>, AS=<optimized out>)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:1030
> #33 0x00007ffff52cd05d in clang::Parser::ParseExternalDeclaration
> (this=this at entry=0x728c60, attrs=..., DS=DS at entry=0x0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:853
> #34 0x00007ffff52ce05c in clang::Parser::ParseTopLevelDecl
> (this=this at entry=0x728c60, Result=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/Parser.cpp:609
> #35 0x00007ffff522ce1b in clang::ParseAST (S=...,
> PrintStats=PrintStats at entry=false,
> SkipFunctionBodies=SkipFunctionBodies at entry=false)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseAST.cpp:146
> #36 0x00007ffff522d0e0 in clang::ParseAST (PP=..., Consumer=0x535f70,
> Ctx=..., PrintStats=<optimized out>, TUKind=clang::TU_Complete,
> CompletionConsumer=0x0,
> SkipFunctionBodies=false) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/clang/lib/Parse/ParseAST.cpp:110
> #37 0x00007ffff74f0059 in lldb_private::ClangExpressionParser::Parse
> (this=this at entry=0x7fffffffcae0, diagnostic_manager=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp:619
> #38 0x00007ffff74d23ad in lldb_private::ClangUserExpression::Parse
> (this=0x6d23c0, diagnostic_manager=..., exe_ctx=...,
> execution_policy=lldb_private::eExecutionPolicyOnlyWhenNeeded,
> keep_result_in_memory=<optimized out>, generate_debug_info=<optimized
> out>)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Plugins/ExpressionParser/Clang/ClangUserExpression.cpp:472
> ---Type <return> to continue, or q <return> to quit---
> #39 0x00007ffff72cea9e in lldb_private::UserExpression::Evaluate
> (exe_ctx=..., options=..., expr=..., prefix=..., result_valobj_sp=...,
> error=..., line_offset=0,
> fixed_expression=0x4bced8, jit_module_sp_ptr=0x0) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Expression/UserExpression.cpp:239
> #40 0x00007ffff7401996 in lldb_private::Target::EvaluateExpression
> (this=this at entry=0x5b8d10, expr=..., exe_scope=<optimized out>,
> result_valobj_sp=...,
> options=..., fixed_expression=0x4bced8) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Target/Target.cpp:2321
> #41 0x00007ffff77912dd in
> lldb_private::CommandObjectExpression::EvaluateExpression
> (this=this at entry=0x4bcb50, expr=expr at entry=0x7fffffffd4c0 "val.v",
> output_stream=output_stream at entry=0x7fffffffd5f0,
> error_stream=error_stream at entry=0x7fffffffd648,
> result=result at entry=0x7fffffffd5f0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Commands/CommandObjectExpression.cpp:377
> #42 0x00007ffff7792018 in
> lldb_private::CommandObjectExpression::DoExecute (this=0x4bcb50,
> command=0x7fffffffd4c0 "val.v", result=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Commands/CommandObjectExpression.cpp:625
> #43 0x00007ffff7305baa in lldb_private::CommandObjectRaw::Execute
> (this=0x4bcb50, args_string=0x7fffffffd4c0 "val.v", result=...)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Interpreter/CommandObject.cpp:1013
> #44 0x00007ffff7302e1b in
> lldb_private::CommandInterpreter::HandleCommand
> (this=this at entry=0x4a8740, command_line=<optimized out>,
> lazy_add_to_history=lazy_add_to_history at entry
> =lldb_private::eLazyBoolCalculate,
> result=..., override_context=override_context at entry=0x0,
> repeat_on_empty_command=repeat_on_empty_command at entry=true,
> no_context_switching=false)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:1683
> #45 0x00007ffff73047c8 in
> lldb_private::CommandInterpreter::IOHandlerInputComplete
> (this=0x4a8740, io_handler=..., line="expr val.v")
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:2771
> #46 0x00007ffff723e241 in lldb_private::IOHandlerEditline::Run
> (this=0x5b4da0)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Core/IOHandler.cpp:573
> #47 0x00007ffff720a820 in lldb_private::Debugger::ExecuteIOHandlers
> (this=0x4a6f90)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Core/Debugger.cpp:961
> #48 0x00007ffff72f731f in
> lldb_private::CommandInterpreter::RunCommandInterpreter
> (this=0x4a8740, auto_handle_events=auto_handle_events at entry=true,
> spawn_thread=spawn_thread at entry=false, options=...) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/Interpreter/CommandInterpreter.cpp:2971
> #49 0x00007ffff7094776 in lldb::SBDebugger::RunCommandInterpreter
> (this=this at entry=0x7fffffffda60,
> auto_handle_events=auto_handle_events at entry=true,
> spawn_thread=spawn_thread at entry=false) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/source/API/SBDebugger.cpp:892
> #50 0x0000000000404a76 in Driver::MainLoop (this=this at entry
> =0x7fffffffda40)
> at
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/tools/driver/Driver.cpp:1156
> #51 0x0000000000403724 in main (argc=2, argv=0x7fffffffdcb8) at
>
> /home/gerazo/repos/codechecker_dev_env/CTU/llvm/tools/lldb/tools/driver/Driver.cpp:1253
>
> ```
> On Tue, Aug 14, 2018 at 2:34 AM Richard Smith via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
> >
> > On Mon, 13 Aug 2018 at 17:08, Lang Hames via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
> >>
> >> Hi Richard,
> >>
> >>> Perhaps a better approach would be to make the "minimal" mode for the
> ASTImporter provide an ExternalASTSource to lazily complete the AST as
> needed (thereby avoiding violating the invariant, because you would
> populate the lexical declarations list whenever anyone actually asks for
> it).
> >>
> >>
> >> This seems worth investigating. I wonder if it might also fix another
> bug that I know of involving virtual methods with covariant return types.
> (You and I actually discussed it at one of the socials a while back, but I
> have not had time to dig into it further.)
> >>
> >> The reproducer for the bug is:
> >>
> >> class Foo {};
> >> class Bar : public Foo {};
> >>
> >> class Base {
> >> public:
> >> virtual Foo* foo() { return nullptr; }
> >> };
> >>
> >> class Derived : public Base {
> >> public:
> >> virtual Bar* foo() { return nullptr; }
> >> };
> >>
> >> int main() {
> >> Derived D;
> >> D.foo(); // Evaluate 'D.foo()' here, crash LLDB.
> >> }
> >>
> >> The issue is that since Bar's definition is not used its bases are
> never imported, and so the call to Bar::bases() crashes in CodeGen. If we
> provided an ExternalASTSource, would that be able to lazily complete the
> bases?
> >
> >
> > Yes, such an approach should be able to solve that problem too: when
> CodeGen (or indeed anything) queries any property of the definition of Foo
> / Bar (including whether a definition exists), you'll get a callback and a
> chance to provide a complete type.
> >
> >>
> >> Cheers,
> >> Lang.
> >>
> >>
> >> On Mon, Aug 13, 2018 at 3:30 PM Richard Smith <richard at metafoo.co.uk>
> wrote:
> >>>
> >>> On Thu, 9 Aug 2018 at 10:47, Lang Hames via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
> >>>>
> >>>> Hi clang-dev, lldb-dev,
> >>>>
> >>>> It looks like my clang commit r305850, which modified ASTImporter to
> import method override tables from an external context, introduced a new
> bug which manifests as incorrect vtable layouts for LLDB expression code.
> >>>>
> >>>> The bug itself is fairly straightforward. In r305850 I introduced the
> following method, which is called from ASTNodeImporter::VisitFunctionDecl:
> >>>>
> >>>> void ASTNodeImporter::ImportOverrides(CXXMethodDecl *ToMethod,
> >>>> CXXMethodDecl *FromMethod) {
> >>>> for (auto *FromOverriddenMethod : FromMethod->overridden_methods())
> >>>> ToMethod->addOverriddenMethod(
> >>>> cast<CXXMethodDecl>(Importer.Import(const_cast<CXXMethodDecl*>(
> >>>> FromOverriddenMethod))));
> >>>> }
> >>>>
> >>>> This will produce the correct override table, but can also cause
> methods in the Base class to be visited in the wrong order. Consider:
> >>>>
> >>>> class Base {
> >>>> public:
> >>>> virtual void bar() {}
> >>>> virtual void foo() {}
> >>>> };
> >>>>
> >>>> class Derived : public Base {
> >>>> public:
> >>>> void foo() override {}
> >>>> };
> >>>>
> >>>> If Derived is imported into a new context before Base, then the
> importer will visit Derived::foo, and (via ImportOverrides) immediately
> import Base::foo, but this happens before Base::bar is imported. As a
> consequence, the decl order on the imported Base class will end up being [
> foo, bar ], instead of [ bar, foo ]. In LLDB expression evaluation this
> manifests as an incorrect vtable layout for Base, with foo occupying the
> first slot.
> >>>>
> >>>> I am looking for suggestions on the right way to fix this. A brute
> force solution might be to always have ASTNodeImporter::VisitRecordDecl
> visit all base classes, then all virtual methods, which would ensure they
> are visited in the original decl order. However I do not know whether this
> covers all paths by which a CXXRecordDecl might be imported, nor whether
> the performance of this solution would be acceptable (it seems like it
> would preclude a lot of laziness).
> >>>>
> >>>> Alternatively we might be able to associate an index with each
> imported decl and sort on that when we complete the type, but that would
> leave imported decls in the wrong order until the type was complete, and
> since I do not know all the use cases for the importer I'm concerned people
> may rely on the decl order before type is complete.
> >>>>
> >>>> Any insight from ASTImporter experts would be greatly appreciated. :)
> >>>
> >>>
> >>> Hi Lang,
> >>>
> >>> It might be interesting to consider how this is addressed by the
> ExternalASTSource interface. There, we have separate "import the lexical
> contents of this AST node (including populating the lexical declarations
> list with all members, in the right order)", "import the lookup results for
> this name in this context (and cache them but don't add them to the list of
> lexical members)" and "import this specific declaration member (but don't
> add it to the list of lexical members)" queries. One could imagine doing
> something similar for the AST importer: when you're performing a minimal
> import but you want to import a method declaration, don't insert it into
> the list of lexical members of the enclosing record. Instead, defer doing
> that until a complete type is required (at that point, you'd need to import
> all the relevant members anyway, including the base classes and virtual
> functions in the right order).
> >>>
> >>> The above approach would violate AST invariants (you'd have a
> declaration whose lexical parent doesn't believe it lexically contains the
> child), but I don't know off-hand whether that would be problematic.
> Perhaps a better approach would be to make the "minimal" mode for the
> ASTImporter provide an ExternalASTSource to lazily complete the AST as
> needed (thereby avoiding violating the invariant, because you would
> populate the lexical declarations list whenever anyone actually asks for
> it).
> >>
> >> _______________________________________________
> >> cfe-dev mailing list
> >> cfe-dev at lists.llvm.org
> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >
> > _______________________________________________
> > cfe-dev mailing list
> > cfe-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20180814/15a064a8/attachment.html>
More information about the cfe-dev
mailing list