This came about when I had to make changes to accomodate borland compilers which didn't like the BOOST_STRONG_TYPEDEF code. I think I originally wanted "Jody Hagins" <jody-boost-011304@atdesk.com> wrote in message news:20041122165456.34f46069.jody-boost-011304@atdesk.com...
On Mon, 22 Nov 2004 12:54:17 -0800 "Robert Ramey" <ramey@rrsd.com> wrote:
I've never really understood this warning - basically it reminds me that I did what I intended to do.
Are you always sure?
bool basic_iarchive_impl::track( basic_iarchive & ar, void * & t ){ object_id_type oid; load(ar, oid);
// if its a reference to a old object if(object_id_type(object_id_vector.size()) > oid){ // we're done t = object_id_vector[oid].address; return false; } return true; }
object_id_vector is a std::vector<>, so it has...
reference operator[](size_type n), where size_type is "unsigned int"
The line that generates the warning wants to convert a "object_id_type" to a "unsigned int" so it can pass the index to operator[]().
However, object_id_type is a class (BOOST_STRONG_DEF) with the following conversion operators...
operator T () const {return t; } \ operator T & () { return t; } \
where T is "unsigned int"
So, in the attempt to convert from object_id_type to "unsigned int", we try both of the operators, and they both match. So, the compiler can not decide which one you want, because your object is non-const. Maybe in this situation, it does not matter, but there are many situations in which this multiple match can cause harm.
So, I think the warnings should be eliminated, to prevent a piece of "bad" use from being overlooked because we get used to seeing these warnings.
The presence of both operators in the BOOST_STRONG_DEF is what causes this ambiguity...
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