science/dlib-cpp: fix build with clang and libc++ 19
As noted in the libc++ 19 release notes [1], std::char_traits<> is now
only provided for char, char8_t, char16_t, char32_t and wchar_t, and any
instantiation for other types will fail.
This causes science/dlib-cpp to fail to compile with clang 19 and
libc++ 19, resulting in errors similar to:
/usr/include/c++/v1/string:820:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned int>'
820 | static_assert(is_same<_CharT, typename traits_type::char_type>::value,
| ^
/wrkdirs/usr/ports/science/dlib-cpp/work/dlib-19.24/dlib/bigint/../unicode/unicode.h:496:26: note: in instantiation of template class 'std::basic_string<unsigned int>' requested here
496 | inline const ustring convert_utf8_to_utf32 (
| ^
/usr/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
| ^These can be fixed by using char32_t instead of uint32_t for the
unichar type.
Also, clang 19 now implements CWG 96 [1], which requires a template
argument list after a 'template' keyword, resulting in errors similar
to:
/wrkdirs/usr/ports/science/dlib-cpp/work/dlib-19.24/dlib/filtering/../global_optimization/find_max_global.h:61:130: error: a template argument list is expected after a name prefixed by the template keyword [-Wmissing-template-arg-list-after-template-kw]
61 | static auto go(T&& f, const matrix<double,0,1>& a) -> decltype(call_function_and_expand_args<max_unpack-1>::template go(std::forward<T>(f),a))
| ^This can be fixed by adding <> after the go identifier.
[1] https://libcxx.llvm.org/ReleaseNotes/19.html#deprecations-and-removals
PR: 281975
Approved by: arrowd (maintainer)
MFH: 2024Q3
(cherry picked from commit e8b1dca33760dc680dcc732dcd3e9c7be1d79e76)