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From: David Abrahams (dave_at_[hidden])
Date: 2004-08-21 17:41:23

Daniel James <daniel_at_[hidden]> writes:

> Hi,
> The attached patch improves the type traits library on Digital
> Mars. Mostly it just selects the correct code to be used, the only new
> code is a new version of boost::is_convertible. Using '...' to
> overload the conversion check works really badly, so I experimented
> with different ways of trying to get it to select the right overload,
> and found one that mostly works. You can see it in the patch. Also,
> when using static cosnt values it can sometimes cause '_m_from' to get
> instantiated -
> causing a link error. To work round this, it uses enums.
> With this patch applied there are still the following problems:
> The compiler has trouble with const and volatile modifiers on voids
> and arrays in template variables. So it gets a lot of the tests
> involving these types wrong.
> The compiler allows some conversions that it shouldn't. For example,
> it only warns about binding temporaries to non-const references,
> instead of causing an error. So, in these cases is_convertible is
> true. Would it be worth adding checks for these cases?
> is_abstract doesn't work.
> is_base_and_derived uses the 'broken' implementation, based on
> is_convertible.
> The test tricky_is_enum_test fails to compile.

Doesn't Walter update DMC++ quite often? Would it be better to just
report bugs to him and wait for the fixes? I have no major objection
to the patches; I'm just slightly concerned about crufting up the
codebase to add support for a previously unsupported compiler if it
will happen without changes in a few weeks anyway.

Dave Abrahams
Boost Consulting

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