[cfe-dev] Fix for PR4701

[David Chisnall]

Hi Daniel,

I've not yet - I don't know my way around the PCH code at all.  I  
believe the problem is that Sema::MergeTypeDefDecl() will be called  
when building the PCH, but not when loading it.  This sets the  
redefinition type, so without the call it is not properly loaded.  The  
fix would make sure that Context.ObjCIdRedefinitionType and  
Context.ObjCClassRedefinitionType were saved in the PCH and loaded  
again afterwards, but I don't know enough about how PCH handling works  
to fix this.

I think the fix is to add lines to PCHWriter::WriteMetadata() to write  
these and corresponding lines in PCHReader:: to restore them, but  
maybe someone who knows how the PCH stuff works could comment?

David

On 20 Aug 2009, at 17:33, Daniel Dunbar wrote:

> David,
>
> Have you had a chance to look at this crash yet? This is preventing us
> from building various projects so I'd like to get it resolved soon.
>
> - Daniel
>
> On Tue, Aug 18, 2009 at 10:39 PM, Daniel Dunbar<daniel at zuster.org>  
> wrote:
>> Ah, the problem appears to be related to the use of PCH:
>> --
>> ddunbar at giles:tmp$ cat t.h
>> #include <Foundation/Foundation.h>
>> ddunbar at giles:tmp$ cat t.m
>> id f0(id x) {
>>  return x->isa;
>> }
>> ddunbar at giles:tmp$ clang -x objective-c-header t.h
>> ddunbar at giles:tmp$ clang -include t.h t.m
>> 0   clang-cc          0x0000000101080755 PrintStackTrace(void*) + 38
>> 1   clang-cc          0x0000000101080ce3 SignalHandler(int) + 336
>> 2   libSystem.B.dylib 0x00007fff812ff83a _sigtramp + 26
>> 3   libSystem.B.dylib 000000000000000000 _sigtramp + 2127562720
>> 4   clang-cc          0x0000000100374eb1
>> clang::ASTContext::getCanonicalType(clang::QualType) + 39
>> 5   clang-cc          0x0000000100262463
>> clang::Sema::ImpCastExprToType(clang::Expr*&, clang::QualType,
>> clang::CastExpr::CastInfo const&, bool) + 123
>> 6   clang-cc          0x00000001002d4635
>> clang::Sema::ActOnMemberReferenceExpr(clang::Scope*,
>> clang::ASTOwningResult<&(clang::ActionBase::DeleteExpr(void*))>,
>> clang::SourceLocation, clang::tok::TokenKind, clang::SourceLocation,
>> clang::IdentifierInfo&, clang::OpaquePtr<0>, clang::CXXScopeSpec
>> const*) + 545
>> 7   clang-cc          0x0000000100429172
>> clang 
>> ::Parser 
>> ::ParsePostfixExpressionSuffix 
>> (clang::ASTOwningResult<&(clang::ActionBase::DeleteExpr(void*))>)
>> + 2624
>> 8   clang-cc          0x000000010042b587
>> clang::Parser::ParseCastExpression(bool, bool, bool&, bool) + 3115
>> 9   clang-cc          0x000000010042ceb7
>> clang::Parser::ParseCastExpression(bool, bool, bool) + 99
>> 10  clang-cc          0x000000010042818c
>> clang::Parser::ParseAssignmentExpression() + 148
>> 11  clang-cc          0x0000000100428616  
>> clang::Parser::ParseExpression() + 42
>> 12  clang-cc          0x0000000100442583
>> clang::Parser::ParseReturnStatement() + 203
>> 13  clang-cc          0x00000001004441cd
>> clang::Parser::ParseStatementOrDeclaration(bool) + 2653
>> 14  clang-cc          0x0000000100447a55
>> clang::Parser::ParseCompoundStatementBody(bool) + 239
>> 15  clang-cc          0x000000010044800b
>> clang::Parser::ParseFunctionStatementBody(clang::OpaquePtr<0>) + 193
>> 16  clang-cc          0x0000000100450e6d
>> clang::Parser::ParseFunctionDefinition(clang::Declarator&,
>> clang::Parser::ParsedTemplateInfo const&) + 1009
>> 17  clang-cc          0x00000001004518d3
>> clang 
>> ::Parser 
>> ::ParseDeclarationOrFunctionDefinition(clang::AccessSpecifier)
>> + 1599
>> 18  clang-cc          0x0000000100451ec2
>> clang::Parser::ParseExternalDeclaration() + 1232
>> 19  clang-cc          0x0000000100451f74
>> clang::Parser::ParseTopLevelDecl(clang::OpaquePtr<1>&) + 106
>> 20  clang-cc          0x0000000100260725
>> clang::ParseAST(clang::Preprocessor&, clang::ASTConsumer*,
>> clang::ASTContext&, bool, bool) + 497
>> 21  clang-cc          0x0000000100030692
>> ProcessInputFile(clang::Preprocessor&, clang::PreprocessorFactory&,
>> std::string const&, ProgActions, llvm::StringMap<bool,
>> llvm::MallocAllocator> const&, llvm::LLVMContext&) + 4175
>> 22  clang-cc          0x000000010003203e main + 2909
>> 23  clang-cc          0x000000010002c550 start + 52
>> Stack dump:
>> 0.      Program arguments:
>> /Volumes/Data/Users/ddunbar/llvm/Debug/bin/clang-cc -triple
>> x86_64-apple-darwin10 -S -disable-free -main-file-name t.m
>> --relocation-model pic -pic-level=1 --disable-fp-elim
>> --unwind-tables=1 --mcpu=core2 --fmath-errno=0
>> -mmacosx-version-min=10.6.0 -include-pch t.h.gch
>> -fdiagnostics-show-option -o
>> /var/folders/DQ/DQ8GT3++HESEzT1obWBynE+++TI/-Tmp-/cc-YvJBuv.s -x
>> objective-c t.m
>> 1.      t.m:2:13: current parser token 'isa'
>> 2.      t.m:1:13: parsing function body 'f0'
>> 3.      t.m:1:13: in compound statement ('{}')
>> clang: error: compiler command failed due to signal 11 (use -v to see
>> invocation)
>> --
>>
>> Probably the state about the redefinition isn't getting properly
>> restored? I don't know much about the PCH implementation, myself...
>>
>>  - Daniel
>>
>>
>> On Tue, Aug 18, 2009 at 8:57 AM, David  
>> Chisnall<csdavec at swansea.ac.uk> wrote:
>>> On 18 Aug 2009, at 16:47, Daniel Dunbar wrote:
>>>
>>>> I think you missed the point here.
>>>>
>>>> If ObjCIdRedefinitionType has not been assigned, then it will be  
>>>> the
>>>> null QualType. The comparison will succeed (since BaseType is not
>>>> null), then BaseType will be assigned to the null type, then the  
>>>> code
>>>> will crash a few lines later.
>>>
>>> Once again, can you provide a test case which demonstrates this?   
>>> I have
>>> tests which attempt to access fields on an id-typed variable with no
>>> definition of id provided, and they do not crash and do use this  
>>> code path.
>>>  If you can demonstrate a condition where this manifests as a bug,  
>>> then I
>>> would be more than happy to fix it.  As, at the moment, it is  
>>> working as I
>>> expect it to work, so I can't fix it because I am not seeing any  
>>> breakage.
>>>
>>> The comparison is only there to avoid a redundant implicit cast  
>>> when there
>>> is one already (which can only happen in cases where a  
>>> redefinition is
>>> supplied).
>>>
>>> David
>>>
>>