1) a corrected version of is_abstract_template_test.cpp
When I prepared the original version I did not realize that is_abstract<T&>::value is supposed to be false for any type T.
2) a patch to boost/type_traits/is_abstract.hpp that works around gcc bug #17232.
I would not be surprised if my patch turns out to be overly complicated. I had assumed that any expression that involves sizeof(T) causes the instantiation of T if T is a template specialization. So I tried, e.g., to add the condition sizeof(T) > 0 to the parameter list of ice_and in is_abstract_imp. For some reason, though, whatever I tried showed no effect. (Perhaps the compiler realized that the conditions I added were true for any type T and eliminated the evaluation of sizeof(T)?)
I finally settled for attached patch that adds a further struct in which SFINAE is used again.
With this patch gcc 3.4.2 passes both is_abstract_test.cpp as well as the attached is_abstract_template_test.cpp.
I still would like to see something like is_abstract_template_test.cpp added to the type_traits tests. It is easy to introduce subtle bugs both in the compiler when implementing SFINAE and template instantiation as well as in the code relying on SFINAE.
I agree, sorry for not getting on top of this, but I will add your tests into the type traits test suite at some point (and the patch as well obviously). Thanks for this, John.