Re: c++/10380: warning about "choosing ... over ..." when there is no choice

Re: c++/10380: warning about "choosing ... over ..." when there is no choice

[nathan]

Synopsis: warning about "choosing ... over ..." when there is no choice

State-Changed-From-To: analyzed->closed
State-Changed-By: nathan
State-Changed-When: Sun Apr 20 13:39:39 2003
State-Changed-Why:
    not a bug. a = c, is equivalent to a.operator= (c)
    The candidate function is A::operator=(A const &)
    There are two user-defined conversion sequences to convert
    'c' to 'A const &', these are
    1) const qualify C, apply C::operator A () const
    2) apply C::operator B (), convert to A const &
    these are indistinguishable conversion sequences, and 
    therefore the call is ill-formed. G++ is not so picky about
    things, and finds a conversion that works, but might not be the one you expected.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10380

Re: c++/10380: warning about "choosing ... over ..." when there is no choice

[bangerth]

Synopsis: warning about "choosing ... over ..." when there is no choice

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Apr 11 19:44:54 2003
State-Changed-Why:
    Confirmed. Essentially a duplicate of 10337, but with
    slightly different code.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10380

c++/10380: warning about "choosing ... over ..." when there is no choice

[stip]

>Number:         10380
>Category:       c++
>Synopsis:       warning about "choosing ... over ..." when there is no choice
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 11 19:16:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     stip@mathematik.uni-ulm.de
>Release:        unknown-1.0
>Organization:
>Environment:
gcc 3.2 on Solaris 2.9
>Description:
gcc produces warning about chosing one conversion operator over another in the following example where there is only one correct choice:

struct A
{
};

struct B : public A
{
};

class C {
    public:
        operator A() const { return A(); }
        operator B() { return B(); }
};

int
main()
{
    C c;

    A a;
    B b;

    a = c;
    b = c;

    return 0;
}

According to the standard IMO there is no reason to complain but the second conversion operator B() has
to be chosen in both assignments. There is no way to (correctly) apply the first conversion operator, so why
warning about the possibility?
There is no switch to turn exactly this warning off what makes it even worse.
>How-To-Repeat:
g++ 
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: