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 cad/kicad to fail to compile with clang 19 and libc++ 19,
resulting in errors similar to:
/wrkdirs/usr/ports/cad/kicad/work/kicad-7.0.2/thirdparty/nanodbc/nanodbc/nanodbc.cpp:261:25: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
261 | auto const n = std::char_traits<NANODBC_SQLCHAR>::length(array);
| ^
/usr/include/c++/v1/__string/char_traits.h:45:8: note: template is declared here
45 | struct char_traits;
| ^
/wrkdirs/usr/ports/cad/kicad/work/kicad-7.0.2/thirdparty/nanodbc/nanodbc/nanodbc.cpp:3576:52: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
3576 | dsn.name = string(&name[0], &name[std::char_traits<NANODBC_SQLCHAR>::length(name)]);
| ^
/usr/include/c++/v1/__string/char_traits.h:45:8: note: template is declared here
45 | struct char_traits;
| ^
/wrkdirs/usr/ports/cad/kicad/work/kicad-7.0.2/thirdparty/nanodbc/nanodbc/nanodbc.cpp:3578:49: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
3578 | string(&driver[0], &driver[std::char_traits<NANODBC_SQLCHAR>::length(driver)]);
| ^
/usr/include/c++/v1/__string/char_traits.h:45:8: note: template is declared here
45 | struct char_traits;
| ^
/wrkdirs/usr/ports/cad/kicad/work/kicad-7.0.2/thirdparty/nanodbc/nanodbc/nanodbc.cpp:3629:54: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
3629 | drv.name = string(&descr[0], &descr[std::char_traits<NANODBC_SQLCHAR>::length(descr)]);
| ^
/usr/include/c++/v1/__string/char_traits.h:45:8: note: template is declared here
45 | struct char_traits;
| ^
and:
/usr/include/c++/v1/string:820:42: error: implicit instantiation of undefined template 'std::char_traits<unsigned short>'
820 | static_assert(is_same<_CharT, typename traits_type::char_type>::value,
| ^
/wrkdirs/usr/ports/cad/kicad/work/kicad-7.0.2/thirdparty/compoundfilereader/compoundfilereader.h:226:21: note: in instantiation of template class 'std::basic_string<unsigned short>' requested here
226 | utf16string dir;
| ^
/usr/include/c++/v1/__fwd/string.h:23:29: note: template is declared here
23 | struct _LIBCPP_TEMPLATE_VIS char_traits;
| ^
The first batch of errors can be fixed by providing a simple `length()`
function for the `NANODBC_SQLCHAR const*` type. The second batch can be
fixed by using `std::basic_string<char16_t>` for `utf16string`, and
adjusting the call to `std::basic_string<char16_t>::append`.
[1] https://libcxx.llvm.org/ReleaseNotes/19.html#deprecations-and-removals
PR: 281886
MFH: 2024Q3
