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From: "meng at g dot clemson.edu" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/55386] New: operator void called for class objects converted to void type.
Date: Mon, 19 Nov 2012 01:13:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55386

             Bug #: 55386
           Summary: operator void called for class objects converted to
                    void type.
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: meng@g.clemson.edu


C++11 12.3.2/1 says that:
A conversion function is never used to convert a (possibly cv-qualified) object
to the (possibly cv-qualified) same object type (or a reference to it), to a
(possibly cv-qualified) base class of that type (or a reference to
it), or to (possibly cv-qualified) void.

The standard also puts a note at the end of same page which reads:
A conversion to void does not invoke any conversion function (5.2.9).

But the following program shows that g++ calls operator void for class objects
converted to the void type.

--------------------- BEGIN ---------------------
#include <iostream>

struct test
{
 operator void () const { std::cout << "test::operator void ()" << std::endl; }
};

int main ()
{
 test const t;
 (void)t; // calls test::operator void
 return 0;
}
---------------------  END  ---------------------

My command line:~/gcc/4.7.0/bin/c++ -std=c++11 -Wall -Wextra t.cc
My compiler version:~/gcc/4.7.0/bin/c++ -v
Reading specs from /home/meng/gcc/4.7.0/lib/gcc/i686-pc-linux-gnu/4.7.0/specs
COLLECT_GCC=/home/meng/gcc/4.7.0/bin/c++
COLLECT_LTO_WRAPPER=/home/meng/gcc/4.7.0/libexec/gcc/i686-pc-linux-gnu/4.7.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ./configure --prefix=/home/meng/gcc/4.7.0/
--enable-languages=c,c++
Thread model: posix
gcc version 4.7.0 (GCC)