Reduce function deferral in g++

[Geoffrey Keating]

On 24/05/2004, at 6:18 PM, Jason Merrill wrote:

> On Mon, 24 May 2004 13:54:36 -0700 (PDT), gkeating@apple.com (Geoffrey 
> Keating) wrote:
>
>> 	* pt.c (mark_decl_instantiated): Only call defer_fn if
>> 	the function actually needs processing in finish_file.
>
> I'm pretty sure this is wrong; this looks like it would avoid emitting
> members of an explicitly instantiated template class.

I was somewhat surprised to find out that this is not, in fact, true.  
What happens is that every time mark_decl_instantiated is called, it is 
called like this:

   mark_decl_instantiated (result, extern_p);
   repo_template_instantiated (result, extern_p);
   if (! extern_p)
     instantiate_decl (result, /*defer_ok=*/1);

and instantiate_decl actually does the work of outputting the function, 
through a complicated mechanism.

[I also checked this with a testcase, and I found that

template <class T> class Z {
   T foo () { return 2; }
};

template class Z<char>;

does in fact output Z<char>::foo().]

> However, I don't see any reason to defer the function if extern_p is 
> true.

Now I'm beginning to wonder if we need to call defer_fn here at all.