Overload resolution and copy constructors that take non-const references

Hi,

Should the following compile, and what should it print?

#include <memory>
#include <iostream>

void foo(std::auto_ptr<int> x)
{
    std::cout<<"copy"<<std::endl;
}

struct dummy
{
    dummy(std::auto_ptr<int> const&)
    {}
};

void foo(dummy x)
{
    std::cout<<"dummy const ref"<<std::endl;
}

int main()
{
    std::auto_ptr<int> const x(new int);
    foo(x);
}

MSVC 9.0 and g++ 4.3 disagree.

MSVC compiles it and prints "dummy const ref", which is what I expected.

g++ refuses to compile it, saying that:

test_copy.cpp: In function 'int main()':
test_copy.cpp:23: error: passing 'const std::auto_ptr<int>' as 'this' argument o
f 'std::auto_ptr<_Tp>::operator std::auto_ptr_ref<_Tp1>() [with _Tp1 = int, _Tp
= int]' discards qualifiers
test_copy.cpp:23: error: initializing argument 1 of 'void foo(std::auto_ptr<in
t>)'

implying that it chose the first overload of foo.

Anthony
--
Anthony Williams | Just Software Solutions Ltd
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