can't running...

[smarttang]

Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
"/Library/Developer/CommandLineTools/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.12.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name Get.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu penryn -target-linker-version 278.4 -v -dwarf-column-info -debugger-tuning=lldb -resource-dir /Library/Developer/CommandLineTools/usr/bin/../lib/clang/8.1.0 -I include -stdlib=libc++ -w -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /Users/smarttang/http -ferror-limit 19 -fmessage-length 104 -stack-protector 1 -fblocks -fobjc-runtime=macosx-10.12.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/x2/6cnhw24969s1f0v1h099qgdr0000gn/T/Get-483293.o -x c++ Get.cpp
clang -cc1 version 8.1.0 (clang-802.0.42) default target x86_64-apple-darwin16.7.0
ignoring nonexistent directory "/usr/include/c++/v1"
#include "..." search starts here:
#include <...> search starts here:
include
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1
/usr/local/include
/Library/Developer/CommandLineTools/usr/bin/../lib/clang/8.1.0/include
/Library/Developer/CommandLineTools/usr/include
/usr/include
/System/Library/Frameworks (framework directory)
/Library/Frameworks (framework directory)
End of search list.
"/Library/Developer/CommandLineTools/usr/bin/ld" -demangle -lto_library /Library/Developer/CommandLineTools/usr/lib/libLTO.dylib -no_deduplicate -dynamic -arch x86_64 -macosx_version_min 10.12.0 -w -o a.out /var/folders/x2/6cnhw24969s1f0v1h099qgdr0000gn/T/Get-483293.o -lc++ -lSystem /Library/Developer/CommandLineTools/usr/bin/../lib/clang/8.1.0/lib/darwin/libclang_rt.osx.a
Undefined symbols for architecture x86_64:
"coro::hub()", referenced from:
std::__1::shared_ptrcoro::Coroutine coro::startmain::$_0(main::$_0) in Get-483293.o
"coro::run()", referenced from:
_main in Get-483293.o
"coro::Stack::Stack(unsigned int)", referenced from:
coro::Coroutine::Coroutinemain::$_0(main::$_0) in Get-483293.o
"coro::Stack::~Stack()", referenced from:
coro::Coroutine::Coroutinemain::$_0(main::$_0) in Get-483293.o
"coro::Coroutine::init(std::__1::function<void ()> const&)", referenced from:
coro::Coroutine::Coroutinemain::$_0(main::$_0) in Get-483293.o
"coro::Coroutine::~Coroutine()", referenced from:
std::__1::shared_ptrcoro::Coroutine::shared_ptrcoro::Coroutine(coro::Coroutine*, std::__1::enable_if<is_convertible<coro::Coroutine*, coro::Coroutine*>::value, std::__1::shared_ptrcoro::Coroutine::__nat>::type) in Get-483293.o
std::__1::__shared_ptr_pointer<coro::Coroutine*, std::__1::default_deletecoro::Coroutine, std::__1::allocatorcoro::Coroutine >::__on_zero_shared() in Get-483293.o
"http::get(std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator > const&, std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator > const&)", referenced from:
main::$_0::operator()() const in Get-483293.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)