[ytti@ytti.fi ~/usr/git/sykemittari]% crystal build --release moi.cr [ytti@ytti.fi ~/usr/git/sykemittari]% ~/usr/git/crystal/.build/crystal build --release moi.cr ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `__crystal_main': main_module:(.text+0x411a): undefined reference to `co_thread_init' main_module:(.text+0x41e4): undefined reference to `co_set_data' main_module:(.text+0x4a86): undefined reference to `co_get_data' main_module:(.text+0x53ab): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `*Fiber::new<&( -> Void)>:Fiber': main_module:(.text+0x6a86): undefined reference to `co_set_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `*Fiber#resume<Fiber>:Void': main_module:(.text+0x6f60): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `*IO::FileDescriptor#unbuffered_write<IO::FileDescriptor, Slice(UInt8)>:Int32': main_module:(.text+0x7559): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `~fun_literal_12': main_module:(.text+0x7e24): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `~fun_literal_19': main_module:(.text+0xb561): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o: In function `*TCPServer@IO::Buffered#flush<TCPServer>:TCPServer': main_module:(.text+0xc25a): undefined reference to `co_get_data' ./.crystal/home/ytti/usr/git/sykemittari/moi.cr/_main.o:main_module:(.text+0xe359): more undefined references to `co_get_data' follow collect2: error: ld returned 1 exit status Error: execution of command failed with code: 1: `cc -o "moi" "${@}" -rdynamic -lssl -lcrypto -levent -lrt -lpcl -lpcre -lgc -lpthread -ldl` [1 ytti@ytti.fi ~/usr/git/sykemittari]% cat moi.cr require "http/server" server = HTTP::Server.new(1122) do |request| ##pp request.src ##pp request.dst HTTP::Response.ok "text/plain", "yaya" end server.listen [ytti@ytti.fi ~/usr/git/sykemittari]%