C++ 将问题与{fmt}6.2.1-3和#x2B联系起来；尝试使用ostream时发出叮当声10.0.0<&书信电报；运算符对象

在std:：thread的get_id（）和通过fmt打印（尽管我包括fmt/ostream.h）出现问题后，我想我应该把这个简单的fmt_test.cpp文件放在一起（基于以下内容）：

#包括
#包括
#包括
上课日期{
年、月、日；
公众：
日期（整年、整月、整日）：
m_年（年），
m_月（月），
m_日（日）
{}
friend std:：ostream&operator这看起来像是pacman包的问题，因为您的示例使用的是{fmt}的股票版本6.2.1:。我建议检查pacman版本的libfmt导出的符号。
这是否回答了您的问题？尝试重载Hmm时出错，但即使无法重现您的问题，我也会遇到此问题，谢谢！经过进一步调查，如果我删除“-stdlib=libc++”，似乎可以工作pacman包可能是用libstdc++编译的。
clang version 10.0.0 
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /sbin
Found candidate GCC installation: /sbin/../lib/gcc/x86_64-pc-linux-gnu/10.1.0
Found candidate GCC installation: /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/10.1.0
Found candidate GCC installation: /usr/lib64/gcc/x86_64-pc-linux-gnu/10.1.0
Selected GCC installation: /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
 "/usr/bin/clang-10" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name fmt_test.cpp -mrelocation-model pic -pic-level 2 -pic-is-pie -mthread-model posix -mframe-pointer=all -fmath-errno -fno-rounding-math -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining -debug-info-kind=limited -dwarf-version=4 -debugger-tuning=gdb -v -resource-dir /usr/lib/clang/10.0.0 -internal-isystem /usr/bin/../include/c++/v1 -internal-isystem /usr/local/include -internal-isystem /usr/lib/clang/10.0.0/include -internal-externc-isystem /include -internal-externc-isystem /usr/include -O0 -std=c++20 -fdeprecated-macro -fdebug-compilation-dir /home/falk/Code/Sandbox -ferror-limit 19 -fmessage-length 0 -stack-protector 2 -fgnuc-version=4.2.1 -fobjc-runtime=gcc -fcxx-exceptions -fexceptions -fdiagnostics-show-option -faddrsig -o /tmp/fmt_test-befb6c.o -x c++ fmt_test.cpp
clang -cc1 version 10.0.0 based upon LLVM 10.0.0 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/bin/../include/c++/v1
 /usr/local/include
 /usr/lib/clang/10.0.0/include
 /usr/include
End of search list.
 "/sbin/ld" -pie --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o testbin /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../lib64/Scrt1.o /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../lib64/crti.o /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/crtbeginS.o -L/sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0 -L/sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../lib64 -L/usr/bin/../lib64 -L/lib/../lib64 -L/usr/lib/../lib64 -L/sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../.. -L/usr/bin/../lib -L/lib -L/usr/lib /tmp/fmt_test-befb6c.o -lfmt -lc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/crtendS.o /sbin/../lib64/gcc/x86_64-pc-linux-gnu/10.1.0/../../../../lib64/crtn.o
/sbin/ld: /tmp/fmt_test-befb6c.o: in function `std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping<char>(fmt::v6::internal::locale_ref)':
/usr/include/fmt/format.h:855: undefined reference to `std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping_impl<char>(fmt::v6::internal::locale_ref)'
/sbin/ld: /tmp/fmt_test-befb6c+.o: in function `void fmt::v6::internal::format_value<char, date>(fmt::v6::internal::buffer<char>&, date const&, fmt::v6::internal::locale_ref)':
/usr/include/fmt/ostream.h:102: undefined reference to `std::__1::locale fmt::v6::internal::locale_ref::get<std::__1::locale>() const'
clang-10: error: linker command failed with exit code 1 (use -v to see invocation)


/sbin/ld: /tmp/fmt_test-d2bca4.o: in function `void fmt::v6::internal::format_value<char, std::__1::__thread_id>(fmt::v6::internal::buffer<char>&, std::__1::__thread_id const&, fmt::v6::internal::locale_ref)':
/usr/include/fmt/ostream.h:102: undefined reference to `std::__1::locale fmt::v6::internal::locale_ref::get<std::__1::locale>() const'
/sbin/ld: /tmp/fmt_test-d2bca4.o: in function `std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping<char>(fmt::v6::internal::locale_ref)':
/usr/include/fmt/format.h:855: undefined reference to `std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > fmt::v6::internal::grouping_impl<char>(fmt::v6::internal::locale_ref)'
clang-10: error: linker command failed with exit code 1 (use -v to see invocation)