[cfe-dev] Review Request: Plain Old Data (POD) property of classes, and type traits basics

[Douglas Gregor]

Hi Sebastian,

On Jan 2, 2009, at 6:57 PM, Sebastian Redl wrote:
> I've implemented the POD property of classes, and (in order to test  
> it)
> a basic infrastructure for GCC's type traits extensions, plus a  
> concrete
> implementation of the __is_pod trait.

Cool.

>
> However, I'm not quite sure about all aspects of the patch, so I'm
> posting it for review first. In particular, I have an enum called
> UnaryTypeTrait that represents the various type trait keywords.  
> Since it
> is needed in the parser, the sema and the AST, I saw no other choice  
> but
> to make it part of Basic. Is this the right thing to do?

Yes, I think so. AccessSpecifier, which currently lives in Parse,  
should also be moved back to Basic (but that's my problem, not yours).

+/// UnaryTypeTraitExpr - A GCC or MS unary type trait, as used in the
+/// implementation of TR1/C++0x type trait templates.

Please add an example to the documentation for this class.

+  // FIXME: Some of the type traits have requirements. Interestingly,  
only the
+  // __is_base_of requirement is explicitly stated to be diagnosed.  
Indeed,
+  // G++ accepts __is_pod(Incomplete) without complaints, and claims  
that the
+  // type is indeed a POD.

Interesting. The documentation for __is_pod says:

	Requires: type shall be a complete type, an array type of unknown  
bound, or is a void type.

So GCC should be diagnosing this kind of error. We should report the  
problem to them. However, we can address this FIXME later. The point  
of the patch is PODs, right? :)

In Type::isPODType, could you add a FIXME for pointer-to-member types?  
(I almost want to just add basic pointer-to-member support now, since  
we seem to have lots of FIXMEs for them).

Regarding the FIXME at the end of  
CXXRecordDecl::hasConstCopyAssignment, I think we should assert that  
the CXXRecordDecl itself is marked "invalid". We shouldn't get here in  
any well-formed program.

This patch looks really good to me. Thanks!

	- Doug