shows nothing on godbolt, but when run on my local machine yields the expected

    $ clang++ bar.cpp -fsanitize=memory -DFMT_HEADER_ONLY=1 -std=c++20
    $ ./a.out
    42
    ==269465==WARNING: MemorySanitizer: use-of-uninitialized-value
        #0 0x55ba20d00c8e in fmt::v8::appender fmt::v8::detail::write<char, fmt::v8::appender, int, 0>(fmt::v8::appender, int) (/tmp/a.out+0xb9c8e)
        #1 0x55ba20cff0ac in fmt::v8::appender fmt::v8::detail::default_arg_formatter<char>::operator()<int>(int) (/tmp/a.out+0xb80ac)
        #2 0x55ba20d6ef67 in char const* fmt::v8::detail::parse_replacement_field<char, void fmt::v8::detail::vformat_to<char>(fmt::v8::detail::buffer<char>&, fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<std::conditional<std::is_same<fmt::v8::type_identity<char>::type, char>::value, fmt::v8::appender, std::back_insert_iterator<fmt::v8::detail::buffer<fmt::v8::type_identity<char>::type> > >::type, fmt::v8::type_identity<char>::type> >, fmt::v8::detail::locale_ref)::format_handler&>(char const*, char const*, void fmt::v8::detail::vformat_to<char>(fmt::v8::detail::buffer<char>&, fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<std::conditional<std::is_same<fmt::v8::type_identity<char>::type, char>::value, fmt::v8::appender, std::back_insert_iterator<fmt::v8::detail::buffer<fmt::v8::type_identity<char>::type> > >::type, fmt::v8::type_identity<char>::type> >, fmt::v8::detail::locale_ref)::format_handler&) (/tmp/a.out+0x127f67)
        #3 0x55ba20cfaca9 in void fmt::v8::detail::vformat_to<char>(fmt::v8::detail::buffer<char>&, fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<std::conditional<std::is_same<fmt::v8::type_identity<char>::type, char>::value, fmt::v8::appender, std::back_insert_iterator<fmt::v8::detail::buffer<fmt::v8::type_identity<char>::type> > >::type, fmt::v8::type_identity<char>::type> >, fmt::v8::detail::locale_ref) (/tmp/a.out+0xb3ca9)
        #4 0x55ba20cf8a57 in fmt::v8::vprint(_IO_FILE*, fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<fmt::v8::appender, char> >) (/tmp/a.out+0xb1a57)
        #5 0x55ba20cf86c2 in fmt::v8::vprint(fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<fmt::v8::appender, char> >) (/tmp/a.out+0xb16c2)
        #6 0x55ba20cf7cce in main (/tmp/a.out+0xb0cce)
        #7 0x7f45c65b330f in __libc_start_call_main libc-start.c
        #8 0x7f45c65b33c0 in __libc_start_main@GLIBC_2.2.5 (/usr/lib/libc.so.6+0x2d3c0)
        #9 0x55ba20c6a444 in _start (/tmp/a.out+0x23444)
    
    SUMMARY: MemorySanitizer: use-of-uninitialized-value (/tmp/a.out+0xb9c8e) in fmt::v8::appender fmt::v8::detail::write<char, fmt::v8::appender, int, 0>(fmt::v8::appender, int)
    Exiting