conversion operator ambiguity

From:

seaswar <seaswar@yahoo.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 10 Feb 2011 17:04:50 CST

Message-ID:

<ceed4cac-ccc7-4c6e-aa2d-add26f6db4cc@x4g2000prf.googlegroups.com>

Could someone please throw some light or suggest a fix to the
ambiguous overload errors that gcc is complaining about? It only seems
to happen in the presence of multiple conversion operators. If if
remove lines A and B, then it compiles.

#include <string>

struct C {
    std::string s; int i;

    operator std::string() const { return s; }

    operator int() const { return i; } // line A
};

int main()
{
    C c;
    std::string s;
    int i;
    s = c;
    i = c; // line B
}

$ g++ --version
g++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-48)

$ g++ -o tp tp.cpp
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/
bits/basic_string.h:485: note: candidates are:
std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT,
_Traits, _Alloc>::operator=(const std::basic_string<_CharT, _Traits,
_Alloc>&) [with _CharT = char, _Traits = std::char_traits<char>,
_Alloc = std::allocator<char>]
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/
bits/basic_string.h:493: note:
std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT,
_Traits, _Alloc>::operator=(const _CharT*) [with _CharT = char,
_Traits = std::char_traits<char>, _Alloc = std::allocator<char>] <near
match>
/usr/lib/gcc/x86_64-redhat-linux/4.1.2/../../../../include/c++/4.1.2/
bits/basic_string.h:504: note:
std::basic_string<_CharT, _Traits, _Alloc>& std::basic_string<_CharT,
_Traits, _Alloc>::operator=(_CharT) [with _CharT = char, _Traits =
std::char_traits<char>, _Alloc = std::allocator<char>]

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