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From: "rui.maciel at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/53281] New: poor error message for calling a non-const method from a const object
Date: Tue, 08 May 2012 13:27:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D53281

             Bug #: 53281
           Summary: poor error message for calling a non-const method from
                    a const object
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rui.maciel@gmail.com


Consider the following code:

<code>
class Foo {
        void bar1() {}
        void bar2(Foo const &foo) {
                foo.bar1();
        }=20=20=20
};

int main()
{
        return 0;
}
</code>

When this code is compiled with g++, the following error message is shown:

<message>
main.c++: In member function =E2=80=98const void Foo::bar2(const Foo&)=E2=
=80=99:
main.c++:4:26: error: passing =E2=80=98const Foo=E2=80=99 as =E2=80=98this=
=E2=80=99 argument of =E2=80=98const void
Foo::bar1()=E2=80=99 discards qualifiers [-fpermissive]
</message>

The error message is technically correct.  Yet, it is too cryptic and a bit
unhelpful, to the point it may be considered that the point of this error
message is entirely missed.=20=20

As an alternative, it would be nice if g++ displayed an error message which
would actually be straight-forward and provided a clear description of the
problem at hand, such as "trying to call a non-const method from a const
object".