I stumble on another problem when trying to compile the test library with IBM/VisualAge (vacpp). Apparantly vacpp has a problem on lines 97,98 and 99 of boost/test/detail/basic_cstring/basic_cstring.hpp. Basically the problem is this: this file declares a class template < class CharT > class basic_string { public: typedef basic_string<CharT> self_type ; self_type& trim_left(self_type exclusions = self_type() ) ; // line 97 } ; If I now remove the default initializer, vacpp does not choke anymore (same situation on lines 98 and 99). I tried to isolate this problem in small test but in a small test vacpp seems to deal with the situation just fine. Thus AFAICT this is a compiler-bug but would anyone mind if I remove the default initializers or just remove them in the vacpp compilation to get one step closer to running the regression tests on vacpp again.