From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Mitchell <mmitchell@usa.net>
To: oliva@dcc.unicamp.br
Cc: jbuck@synopsys.com, als@tusc.com.au, egcs@cygnus.com
Subject: Re: error message formatting
Date: Thu, 16 Apr 1998 23:59:00 -0000
Message-id: <199804162313.QAA29122@mail.earthlink.net>
References: <199804151709.KAA24258@atrus.synopsys.com> <199804160703.AAA01943@mail.earthlink.net> <orwwcp8r1d.fsf@narizinho.lsd.dcc.unicamp.br>
X-SW-Source: 1998-04/msg00670.html

>>>>> "Alexandre" == Alexandre Oliva <oliva@dcc.unicamp.br> writes:

    Alexandre> Mark Mitchell writes:

    >> We have to be careful that we don't introduce ambiguity in the
    >> process.  It may be possible to do so by dropping defaulted
    >> arguments,

    >> template <class T, class U = T**> void f();

    >> template <class T*, class U = T*> void f();

    Alexandre> `classs T*' is not a valid template argument
    Alexandre> declaration.

Thank you for the improved example.  I *knew* when I wrote what I did
that I didn't have it right, but I didn't have time to think about it
carefully.  What an embarrassing mistake!

    Alexandre> However, the raised issue is a valid one.  Suppose one
    Alexandre> declares:

    Alexandre> template <typename T, int i = 1> void f(); template
    Alexandre> <typename T, char e = '\0'> void f();

    Alexandre> Then he calls f<int>().  The compiler must report an
    Alexandre> ambiguity but, if we remove trailing default arguments,
    Alexandre> the error message would look like:

    Alexandre> ?:?:Template function call is ambiguous.  Available
    Alexandre> specializations are: ?:?: f<int>() ?:?: f<int>()

    Alexandre> This would seem rather confusing, although line numbers
    Alexandre> might help.

    Alexandre> -- Alexandre Oliva mailto:oliva@dcc.unicamp.br
    Alexandre> mailto:aoliva@acm.org http://www.dcc.unicamp.br/~oliva
    Alexandre> Universidade Estadual de Campinas, SP, Brasil

-- 
Mark Mitchell <mmitchell@usa.net>
http://home.earthlink.net/~mbmitchell
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