Re: [PATCH] PR c++/26693

[Dodji Seketeli <dodji at redhat dot com>]

Jason Merrill a Ãcrit :
> Dodji Seketeli wrote:
> > -      && uses_template_parms (DECL_CONTEXT (decl)))
> > +      && uses_template_parms (DECL_CONTEXT (decl))
> > +      && uses_template_parms (decl))
>
> This seems wrong.  Why wouldn't we want to re-use typedefs with 
> non-dependent types?

Ah, I did this as a stop gap measure because otherwise for a 
non-dependent typedef variant, the compiler was crashing in tree 
gen_args = tsubst (DECL_TI_ARGS (decl), args, complain, in_decl);

I should have investigated. Earlier. Now it seems it is crashing 
eventualy in tsusbt () because of the assert gcc_assert (TREE_VEC_LENGTH 
(args) > 0); around line 9060. This is because we are trying to tsubst a 
 TEMPLATE_PARM_INDEX with a NULL args parameter. I am not sure why the 
assert would be required there. Just handling the arg == NULL case seems 
to fix it.


> > +          if (!enforce_access (TYPE_BINFO (DECL_CONTEXT (decl)), 
> > decl, decl))
> > +        return error_mark_node;
>
> It occurs to me that just using TYPE_BINFO (DECL_CONTEXT (decl)) may not 
> be enough for code that accesses a typedef through a derived class, i.e.
>
> class A
> {
>  protected:
>   typedef int mytype;
> };
>
> template <class T> class B;
>
> class C: public A
> {
>   template <class T> friend class B;
> };
>
> template <class T> class B
> {
>   C::mytype mem;
> };
>
> B<int> b;
>
> This is valid, but I believe your patch will cause us to reject it, 
> which would be a regression.

Good catch.

Now I guess in this particular case, the right TYPE_BINFO to pass to 
enforce_access() would be the one of the C type, in C::mytype. If that 
is correct then how can I have access to that C type from withing 
tsubst() when I am tsubsting mytype, which TYPE_DECL points to the 
declaration "typedef int mytype;" from class A ? If I can't get that

> > +  name = TYPE_IDENTIFIER (TREE_TYPE (TYPE_MAIN_DECL (type)));
>
> Is this different from TYPE_IDENTIFIER (TYPE_MAIN_VARIANT (type))?

It seems like both are equal actually.

Dodji.