Re: [C++-0X] User-defined literals

[Jason Merrill <jason at redhat dot com>]

On 03/28/2011 08:13 PM, Ed Smith-Rowland wrote:

Please CC me on C++ questions, as I don't keep up with the mailing list 
very well.

> I would like to check that template literal operators have the specific
> non-type parameter pack:
> template<char...>
> Foo operator"" sluggo();
>
> I looked through the internals documentation and didn't see much on
> this. Could anyone give me some pointers?

If you're looking at the PARM_DECL for the template parameter, you want 
to check that TREE_TYPE (decl) is char_type_node and that 
TEMPLATE_PARM_PARAMETER_PACK (DECL_INITIAL (decl)) is true.  Does that help?

> Also, is there any preference for using VEC vs. TREE_CHAIN for making
> trees and accessing them? Is one sort of "modern"?

VEC, definitely.

> Finally I am using compparms to verify that a literal operator argument
> list conforms to strings like:
> (const char*)
> (const char*, std::size_t)
> (const wchar_t*, std::size_t)
> ....
> I cant get them to work. I built a set of global trees for the argument
> types that I want to check. The char and number tests work.
> I use things like this to build the argument lists (I neglect the return
> type).
> userdef_lit_char16_str_type
> = build_function_type_list (void_type_node, char16_array_type_node,
> size_type_node, NULL_TREE);
> I'm hoping that this matches
> (const char16_t*, std::size_t)
> but it doesn't.
>
> Ideas?

Looks like the problem is that char16_array_type_node is an array, not a 
pointer.

But I'd suggest walking the parmlist directly rather than create more 
global trees.

Jason