Re: [c++]pt.c:most_specialized_class appears to substitute outer args for inner params

[Larry Evans]

On 11/02/09 22:39, Larry Evans wrote:

The following code around trunk/gcc/cp/pt.c:15514:

15513     partial_spec_args = INNERMOST_TEMPLATE_ARGS (partial_spec_args);
15514     partial_spec_args = tsubst_template_args
15515       (partial_spec_args, outer_args, tf_none, NULL_TREE);

as shown here:

http://gcc.gnu.org/viewcvs/trunk/gcc/cp/pt.c?view=markup&pathrev=153822

appears to substitute outer_args in the place where inner parameters
are located.  Am I reading the code wrong?  I ask because gdb seems to
show this happening with the following code:

--{-- test code --
  struct
outer_arg0
;
  struct
inner_arg0
;
  struct
inner_arg1
;

//#define CLASS_SCOPE_SPECIALIZATION
  template
  < class OuterArg0
  >
  struct
outer_tmpl
{
      template
      < typename InnerArg0
      , typename InnerArg1
      >
      struct
    inner_tmpl
  #ifndef CLASS_SCOPE_SPECIALIZATION
    ;
  #else
    {};
      template
      < typename InnerArg0
      >
      struct
    inner_tmpl
      < InnerArg0
      , inner_arg1
      >
    {
            typedef
          InnerArg0
        inner_typdef
        ;
    };
  #endif
};

#ifndef CLASS_SCOPE_SPECIALIZATION
  template
  < //class OuterArg0
  >
      template
      < typename InnerArg0
      >
      struct
outer_tmpl
  < outer_arg0
  >::
    inner_tmpl
      < InnerArg0
      , inner_arg1
      >
    {
            typedef
          InnerArg0
        inner_typdef
        ;
    };
#endif

    typedef
  outer_tmpl<outer_arg0>
  ::inner_tmpl
  < inner_arg0
  , inner_arg1
  >
  ::inner_typdef //error here.
outer_inner_type
;
--}-- test code --

[snip]
Just adding an outer_tmpl specialization solves the problem:

  template
  <// class OuterArg0
  >
  struct
outer_tmpl
  < outer_arg0
  >
{
      template
      < typename InnerArg0
      , typename InnerArg1
      >
      struct
    inner_tmpl
    ;
};