On Fri, 5 Jul 2024 at 15:48, Phil Phil via Boost-users <boost-users@lists.boost.org> wrote:

I try to port a c++ project to a new environment with clang++-17, libcxx 17 and std=c++17 for x64 Linux. Also, I switched form boost 1.65 to 1.84. Now I start getting errors in boost itself:

/workspace/usr/include/boost/statechart/fifo_worker.hpp:55:45: error: template argument for template type parameter must be a type
55 | template< class Allocator = std::allocator< none > >

I'm not sure if this answers your issue, but from §12.3.4 (p197) of C++ Templates,

Prior to C++17, default template template arguments of a template template argument were ignored (but if the template template parameter has default arguments, they are considered during the instantiation of the template).

HTHs, Rob