[cfe-commits] r139358 - /cfe/trunk/lib/Serialization/ASTReader.cpp

[Argyrios Kyrtzidis]

On Sep 9, 2011, at 8:15 AM, Douglas Gregor wrote:

> 
> On Sep 8, 2011, at 11:44 PM, Argyrios Kyrtzidis wrote:
> 
>> Author: akirtzidis
>> Date: Fri Sep  9 01:44:17 2011
>> New Revision: 139358
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=139358&view=rev
>> Log:
>> [PCH] When loading the decls linked to an identifier, also make them visible
>> in the translation unit.
>> 
>> Modified:
>>   cfe/trunk/lib/Serialization/ASTReader.cpp
>> 
>> Modified: cfe/trunk/lib/Serialization/ASTReader.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReader.cpp?rev=139358&r1=139357&r2=139358&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Serialization/ASTReader.cpp (original)
>> +++ cfe/trunk/lib/Serialization/ASTReader.cpp Fri Sep  9 01:44:17 2011
>> @@ -4841,8 +4841,16 @@
>>    return;
>>  }
>> 
>> +  ASTContext &Ctx = *getContext();
>>  for (unsigned I = 0, N = DeclIDs.size(); I != N; ++I) {
>>    NamedDecl *D = cast<NamedDecl>(GetDecl(DeclIDs[I]));
>> +
>> +    // In C++, translation unit's visible decls map gets emitted in the AST
>> +    // file, but not on C; make the decl visible so it can be looked up.
>> +    if (!Ctx.getLangOptions().CPlusPlus)
>> +      SetExternalVisibleDeclsForName(Ctx.getTranslationUnitDecl(),
>> +                                     DeclarationName(II), D);
>> +
>> 
> 
> This is a bit unfortunate. Creating the lookup table in the translation unit forces the AST to continually maintain that lookup table (e.g., adding entries to it every time a visible declaration is added to the translation unit), which is a cost we'd like to avoid in C. I presume that you only made this change to support the new lookup used in  r139359? I have an alternative suggestion for that...

But adding entries always updated the lookup table, or the lookup in r139359 would not work in non-PCH mode, right ? 
In general I'd find it bad for the AST usefulness if you could not do a lookup in translation unit unless it is on C++.

> 
> 	- Doug