Clang does not compile a g++ project - boost

Question

When trying to compile a g++ project with the clang compiler, there is a strange error showing up.
Here is the snippet of the source file:
std::set<TTransportNetworkId> l_transportNetworkIds;
SelectionResultContainer l_searchResult = p_repo.rootMoc() / LnAny("LNBTS") / LnAny("LNMME");
BOOST_FOREACH(const SelectionResult & l_lnmmeSR, l_searchResult)
{
const MoLnmme & l_lnmme = l_lnmmeSR;
l_transportNetworkIds.insert(*l_lnmme.transportNwId);
}
The error message is:
conditional expression is ambiguous; 'rvalue_probe<Rrom::DataRep::SelectionResultContainer>' can be converted to 'Rrom::DataRep::SelectionResultContainer' and vice versa
BOOST_FOREACH(const SelectionResult & l_lnmmeSR, l_searchResult)
Conditions are:
The file compiles fine with gcc_4.3.2
clang in version 3.2 throws the above error
Already tried to include the latest boost library which results in the same error
My guess is that clang handles rvalue conditions differently than this gcc version does.
clang is supposed to be a drop-in-replacement for gcc, so how can one get rid of this error without touching the source file?
Are there any options in clang which somehow disables these kind of errors?!
UPDATE:
I could create an example source file, which you can reproduce for yourself:
#include <vector>
#include <boost/foreach.hpp>
class A : public std::vector<int>
{
public:
template <class T>
operator const T &() const;
};
void foo(){
A colA;
int b = 1;
BOOST_FOREACH(b, colA)
{
;
}
}
When compiled with clang 3.2 the above error is raised, with some additional insights to where exactly the error occurs:
error: conditional expression is ambiguous; 'rvalue_probe<A>' can be converted to 'A' and vice versa BOOST_FOREACH(b, colA)
expanded from macro 'BOOST_FOREACH' f (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_col) = BOOST_FOREACH_CONTAIN(COL))
expanded from macro 'BOOST_FOREACH_CONTAIN' BOOST_FOREACH_EVALUATE(COL)
expanded from macro 'BOOST_FOREACH_EVALUATE' (true ? boost::foreach_detail_::make_probe((COL), BOOST_FOREACH_ID(_foreach_is_rvalue)) : (COL))
This code is compiled without errors with gcc_4.7.2.
Any ideas why the two compilers behave differently?

Answer 1

I found the solution in this document, see http://www.boost.org/doc/libs/1_43_0/boost/foreach.hpp
Snippet:
// Some compilers do not correctly implement the lvalue/rvalue conversion
// rules of the ternary conditional operator.
# if defined(BOOST_FOREACH_NO_RVALUE_DETECTION)
So, when providing a -DBOOST_FOREACH_NO_RVALUE_DETECTION definition option to clang, the error disappears.
Still the question remains whether gcc or clang is right or wrong on this point.