Invalid downcast warning in boost::lexical_cast when using UBSAN

[arvo@…]

The attempt to lexical_cast an enum class into a std::string produces a warning with UBSAN. GCC version:

g++-6 (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901

CXXFLAGS: -std=c++11 -fsanitize=undefined

Warning text for the attached test program:

(...)/boost/lexical_cast/detail/converter_lexical_streams.hpp:236:43: runtime error: downcast of address 0x7ffddfb77d38 which does not point to an object of type 'basic_unlockedbuf'
0x7ffddfb77d38: note: object is of type 'std::__cxx11::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >'
 69 7f 00 00  e8 ca fb c9 69 7f 00 00  21 dc d8 00 00 00 00 00  21 dc d8 00 00 00 00 00  21 dc d8 00
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'std::__cxx11::basic_stringbuf<char, std::char_traits<char>, std::allocator<char> >'

[arvo@…]

Minimal test program

[Antony Polukhin]

That issue has been fixed ​here in Boost 1.63