[cfe-dev] Smart pointer usage in the Parser/Actions

[steve naroff]

On Dec 19, 2008, at 4:21 PM, Douglas Gregor wrote:

> On Dec 19, 2008, at 3:39 PM, steve naroff wrote:
>> On Dec 19, 2008, at 3:09 PM, Fariborz Jahanian wrote:
>> A variation on the FIXME is to have a subclass of ParmVarDecl (e.g.  
>> ObjCParmVarDecl) that contains the original type (to support method  
>> encoding). This is still wasteful, however the waste is isolated to  
>> ObjC. Note that C++ is already wasting space (with the DefaultArg  
>> slot). Conceptually, I like the idea of having ObjC and C++  
>> subclasses of ParmVarDecl.
>
> I'm not a fan of having separate ObjC/C++ subclasses for Decls  
> unless there are differences in the data we need to store in the AST.

This is true for C++, but that's a separate issue I guess.

> In this case, the difference isn't whether we're in Objective-C or  
> not; it's whether or not the original type is different from the  
> converted type.

I suppose, but ObjC is the only language that currently cares about  
the original type (so it can generate meta data consistent with the  
source).

> So, why not have ParmVarWithOriginalTypeDecl be a subclass of  
> ParmVarDecl, and create ParmVarWithOriginalTypeDecls whenever we've  
> actually performed some kind of promotion of the declaration's type?  
> That will capture all of the information in the source code while  
> not special-casing Objective-C or introducing an extra slot into  
> ParmVarDecls that aren't promoted.

 From a space perspective, I really like that idea! (and it's  
straightforward to implement). Conceptually it's a little odd, but  
that's not very relevant/important...

snaroff

> I've been meaning to do the same thing with FieldDecl, by creating a  
> subclass BitFieldDecl that's has the extra Stmt* containing the  
> bitfield size. The FieldDecl class's interface won't change... but  
> it will perform a dyn_cast<BitFieldDecl> in  
> FieldDecl::getBitWidth(), so that clients of FieldDecl's won't ever  
> have to know about BitFieldDecl.
>
> 	- Doug