The following reply was made to PR libstdc++/4458; it has been noted by GNATS.

From: Martin Sebor <sebor@roguewave.com>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
 	kanze@gabi-soft.de, gcc-bugs@gcc.gnu.org
Cc:  
Subject: Re: libstdc++/4458
Date: Sun, 14 Oct 2001 15:02:40 -0600

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=4458&database=gcc
 
  |>  It's not required to do so for efficiency (see 22.2.1.3.2, p5).
  
  §22.2.1.1.1/1: concerning std::ctype<>::is:
  
      Returns: do_is(m,c)
  
  Can't be any clearer than that.  The function do_is is required by the
  standard to be virtual, which means that the actual function called (and
  thus the actual semantics of the function is) depend on the dynamic type
  of the object.  This is, after all, the whole point behind defining the
  protected virtual functions -- any other interpretation, and having the
  protected interface makes sense.
 
 No, you're quoting the requirement on the primary template, but your
 issue (titled std::ctype<char>::is ...) is with the specialization on
 char. The requirement I referred you to in 22.2.1.3.2, p5 is the one
 that's relevant here. The reason for not calling the virtual function
 from the ctype<char>::is() is, as I said earlier, for efficiency. 
 
 Regards
 Martin