Bug, in the library, I think

[Ken Yarnall]

A student of mine encountered a bug, using gcc 3.0.1.  Her code looks
more or less like

class error {};
#include <iostream>

This causes parsing errors in bits/codecvt.h.  The problem is that
codecvt_base contains an enum (result) which lists "error" as one of its
members.  Code in the indirect derived class codecvt refers to "error"
without qualification.  

This normally isn't a problem, given C++ lookup rules.  However, the
intervening base class is a template, so essentially, "error" is a name
declared in a templated base class (and hence is a dependent name). 
When the compiler sees "error" in codecvt's member functions, it chooses
the global name, generating the parse error.


If I read Stroustrup and the standard correctly, the compiler is
actually doing the right thing (I was surprised by this).  The solution
seems to be to qualify references to  codecvt_base::error.  The advice
in Stroustrup's appendix on technicalities seems to be good --- reduce
or eliminate the use of unqualified names in the presence of templates.

I'm glad to supply more detail if this is insufficient.

Cheers,
Ken

-- 
Ken Yarnall
Dept. of Mathematical Sciences               Lebanon Valley College
Assoc. Professor of Math and CS       (717)867-6085 yarnall@lvc.edu