From: Nicola Musatti (Nicola.Musatti_at_[hidden])
Date: 2007-03-26 09:33:52
Hallo,
unfortunately the recently committed changes to Boost.Optional uncover a bug in
BCB6, i.e. borland 5.6.4 . As 1.34 is going to be the last Boost release to
officially support this compiler, it would be very important to fix this problem
before the release.
I see that currently no tester is running tests for borland 5.6.4; if none is
available I could run the tests locally on my machine and report back or, with a
little hand-holding, run a full regression run.
The bug can be observed by compiling the following very simple source file:
#include <boost/optional.hpp>
#include <sstream>
This result in a rather incomprehensible error message:
[C++ Error] _ctype.h(124): E2034 Cannot convert 'int *' to
'const ctype_base::mask *'
The problem appears to be triggered by the relational operator overloads that
take a none_t as a first argument (don't ask me why!). By commenting out lines
838-866 in boost/optional/optional.hpp the problem disappears.
The only workaround I was able to find is to revert to the previous
implementation of boost/none.hpp, as in the following:
#include <boost/detail/workaround.hpp>
namespace boost {
#if ! BOOST_WORKAROUND(__BORLANDC__, <= 0x564)
namespace detail { struct none_helper{}; }
typedef int detail::none_helper::*none_t ;
none_t const none = ((none_t)0) ;
#else
enum none_t {none = 0};
#endif
} // namespace boost
Given this is such a simple header it may be reasonable not to include
boost/detail/workaround.hpp here and explicitly state the condition. Note that
this problem is not present in borland 5.8.2.
Cheers,
Nicola Musatti