boost::exception uses invalid C++ code

[Chris Jefferson]

boost::exception uses a

std::map<type_info_, shared_ptr<error_info_base> > in error_info_container_impl. This map is copied in clone(). However, type_info_ contains a member which is a reference, so it is not copyable.

The standard says that you can only copy a std::map<T,U> if both T and U are copyable. Some standard libraries don't make use of this requirement, but libc++ does.

The easiest fix to this would be to make type_info_ take it's reference member instead by pointer, and make it copyable.

Before I prepare a full patch, I wondered if anyone had any comments, as this is a fairly big change to boost::exception

[Steven Watanabe]

Actually, the solution is simple:

• Implement the copy constructor
• Use it in clone

The standard only requires the template arguments to be CopyAssignable for assignment, not for copy construction.

[Chris Jefferson]

Patch to info.hpp, using new copy constructor

[Chris Jefferson]

You are right, that is much simpler, and I missed it. Thanks.

The attached patch does exactly this, and fixes all but one bug in libc++ boost::exception (which is a different problem). gcc darwin still passes all tests.