[cfe-dev] Partial Template Specialization

[Yang Chen]

Douglas Gregor wrote:
> On Apr 5, 2012, at 2:16 PM, Yang Chen <chenyang at cs.utah.edu> wrote:
>
>   
>> Hi,
>>
>> I am writing a pass using ASTConsumer. I find that seems some 
>> declarations of partial template specializations  are missing from 
>> TranslationUnitDecl. For example, given the simple code below:
>>
>> template<bool, typename>
>> struct AAA { };
>>
>> template<typename T>
>> struct AAA<true, T>
>> { };
>>
>> I get the following result dumped from MyPass::HandleTranslationUnit() 
>> function, where MyPass is inherited from ASTConsumer.
>>
>> (gdb) p Ctx.getTranslationUnitDecl()->dump()
>> struct __va_list_tag {
>>    unsigned int gp_offset;
>>    unsigned int fp_offset;
>>    void *overflow_arg_area;
>>    void *reg_save_area;
>> };
>> typedef struct __va_list_tag __va_list_tag;
>> template <typename > struct AAA {
>> };
>> $1 = void
>>
>> In the above output, only template class AAA is presented, but the 
>> partial template specialization is missing.
>>     
>
> Yeah, the AST should probably have the class template partial specializations listed here.
>
>   
>> Is this an expected behavior, or is it a Clang bug? Sorry for my vague 
>> description. Hopefully I am not missing anything.
>>     
>
> You can retrieve class template partial specializations of a ClassTemplateDecl using getPartialSpecializations().
>
> 	- Doug
>   

Doug,

Thanks for the reply.

I tried getPartialSpecializations() on ClassTemplateDecl in the above 
example, but it returns an empty SmallVector to me, shown as below: 
(MyVisitor is an inheritance from RecursiveASTVisitor):

bool MyVisitor::VisitClassTemplateDecl(ClassTemplateDecl *D)
{
  llvm::SmallVector<ClassTemplatePartialSpecializationDecl*, 5> ParSpecs;
  D->getPartialSpecializations(ParSpecs);
  unsigned Sz = ParSpecs.size();
  return true;
}

And from gdb:

Breakpoint 1, MyVisitor::VisitClassTemplateDecl (this=0x1c340f0, 
D=0x1c5ec90) at MyClass.cpp:103
... [skipped]
(gdb) p Sz
$1 = 0
(gdb) p D->dump()
template <typename > struct AAA {
}$2 = void

One more thing is that I assume 
VisitClassTemplatePartialSpecializationDecl should capture the partial 
template specialization above, but it doesn't.

Thanks,
- Yang