skynet是为在线游戏服务器打造的轻量级框架，使用c+lua实现，支持linux 。使用这套框架能获得很大收益，其中一个就是，基本只需要用lua开发，很少用到c，提高了开发效率。但是，skynet本身对系统有很大依赖性，安装说明过于简单，没有提及到。所以文章这里总结linux安装skynet问题，希望有所帮助。
skynet的安装过程
git clone https://github.com/cloudwu/skynet.git cd skynet make linux
简单3步，对于很多高版本的系统来说，可能就这3步。但是，低版本系统可能无法安装，如下：
1. gcc版本问题
2. 缺少 readline
3. 缺少 ncurses
4. 缺少 git （非必要项，则要手动下载skynet及3rd下的jemalloc）
5. 缺少 autoconf
所以，这里以CentOS5.5系统做说明，这系统不具备以上几个条件，甚至连git都无法通过包管理来安装。在skynet的编译过程中，如果在make步骤出现错误，要用 make cleanall 清除已编译的文件，不然会出现莫名其妙的错误。
在早期的skynet版本，lua不能清除干净，若是这样，执行：cd 3rd/lua && make clean && cd -
问题1：缺少git
# git clone https://github.com/cloudwu/skynet.git bash: git: command not found
解决：
这里要安装git，在安装git过程中，非常重要一步是安装curl，而这一步会把git所有的依赖装上，如curl和openssl，而git编译时也要找到curl库
yum -y install curl curl-devel wget --no-check-certificate https://www.kernel.org/pub/software/scm/git/git-2.5.2.tar.gz tar -zxf git-2.5.2.tar.gz cd git-2.5.2 ./configure --prefix=/usr make make install
问题2：git https错误
# git clone https://github.com/cloudwu/skynet.git Cloning into 'skynet'... fatal: Unable to find remote helper for 'https'
解决：
很多网友都是说把https换成git解决，但也只是暂时性的。报错是git安装时系统缺少curl导致的，参考问题1重装git
重装git后，如果还不行，应该是git软连接问题，如下修正：
ln -sf /usr/bin/git /bin/git
问题3：缺少readline
lua.c:81:31: error: readline/readline.h: No such file or directory lua.c:82:30: error: readline/history.h: No such file or directory lua.c: In function ‘pushline’: lua.c:311: warning: implicit declaration of function ‘readline’ lua.c:311: warning: assignment makes pointer from integer without a cast lua.c: In function ‘addreturn’: lua.c:342: warning: implicit declaration of function ‘add_history’ make[3]: *** [lua.o] Error 1 make[3]: Leaving directory `/data/git-2.5.2/skynet/3rd/lua' make[2]: *** [linux] Error 2 make[2]: Leaving directory `/data/git-2.5.2/skynet/3rd/lua' make[1]: *** [3rd/lua/liblua.a] Error 2 make[1]: Leaving directory `/data/git-2.5.2/skynet' make: *** [linux] Error 2
解决：
yum -y install readline-devel
问题4：缺少ncurses
cc -std=gnu99 -o lua lua.o liblua.a -lm -Wl,-E -ldl -lreadline /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `PC' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tgetflag' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tgetent' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `UP' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tputs' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tgoto' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tgetnum' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `BC' /usr/lib/gcc/i386-redhat-linux/4.1.2/../../../libreadline.so: undefined reference to `tgetstr' collect2: ld returned 1 exit status make[3]: *** [lua] Error 1 make[3]: Leaving directory `/data/skynet/3rd/lua' make[2]: *** [linux] Error 2 make[2]: Leaving directory `/data/skynet/3rd/lua' make[1]: *** [3rd/lua/liblua.a] Error 2 make[1]: Leaving directory `/data/skynet' make: *** [linux] Error 2
解决：
很多网友说修改Makefile，在SYSLIBS变量中追加” -lncurses “选项，但这样不方便，以后还会遇到这个问题。所以这里建议手动安装readline
yum -y install ncurses-devel wget ftp://ftp.gnu.org/gnu/readline/readline-6.2.tar.gz tar -zxf readline-6.2.tar.gz cd readline-6.2 ./configure --prefix=/usr make SHLIB_LIBS=-lncurses make install ldconfig
备注：
1、国内连接gnu.org网站不是很稳定，可能wget要多试几次。
2、通过ldconfig -p |grep readline可以测试readline的库是否成功加载
3、如果还无法解决，执行以下命令（建议先备份下）：
rm -rf /usr/lib/libreadline* ldconfig
如果是64位机器：
rm -rf /usr/lib64/libreadline* ldconfig
问题5：lua整数编译报错
3rd/lua/luaconf.h:560:2: error: #error "Compiler does not support 'long long'. Use option '-DLUA_32BITS' or '-DLUA_C89_NUMBERS' (see file 'luaconf.h' for details)" In file included from skynet-src/malloc_hook.c:5: 3rd/lua/lua.h:93: error: expected ‘=’,‘,’,‘;’,‘asm’ or ‘__attribute__’ before ‘lua_Integer’ 3rd/lua/lua.h:96: error: expected ‘=’,‘asm’ or ‘__attribute__’ before ‘lua_Unsigned’ 3rd/lua/lua.h:182: warning: type defaults to ‘int’ in declaration of ‘lua_Integer’ 3rd/lua/lua.h:182: error: ‘lua_Integer’ declared as function returning a function 3rd/lua/lua.h:182: warning: parameter names (without types) in function declaration 3rd/lua/lua.h:226: error: expected declaration specifiers or ‘...’ before ‘lua_Integer’ 3rd/lua/lua.h:244: error: expected declaration specifiers or ‘...’ before ‘lua_Integer’ 3rd/lua/lua.h:246: error: expected declaration specifiers or ‘...’ before ‘lua_Integer’ 3rd/lua/lua.h:261: error: expected declaration specifiers or ‘...’ before ‘lua_Integer’ 3rd/lua/lua.h:263: error: expected declaration specifiers or ‘...’ before ‘lua_Integer’ skynet-src/malloc_hook.c: In function ‘update_xmalloc_stat_alloc’: skynet-src/malloc_hook.c:55: warning: value computed is not used skynet-src/malloc_hook.c: In function ‘update_xmalloc_stat_free’: skynet-src/malloc_hook.c:65: warning: value computed is not used skynet-src/malloc_hook.c: In function ‘dump_mem_lua’: skynet-src/malloc_hook.c:237: error: too many arguments to function ‘lua_pushinteger’ skynet-src/malloc_hook.c:238: error: expected ‘)’ before ‘data’ skynet-src/malloc_hook.c:238: error: too many arguments to function ‘lua_rawseti’ In file included from skynet-src/skynet_log.c:1: skynet-src/skynet_log.h:14:7: warning: no newline at end of file make[1]: *** [skynet] Error 1 make[1]: Leaving directory `/data/skynet' make: *** [linux] Error 2
解决：
这个是skynet最常见的编译失败了，和gcc版本有关，升级gcc可以解决问题。
最简单的方法：修改Makefile，在CFLAGS 加入 -std=gnu99
如果不想手动改，可用以下命令：
sed -i "s|CFLAGS =|CFLAGS = -std=gnu99 |" Makefile
问题6：gcc编译器问题
/data/skynet/skynet-src/skynet_server.c:211: undefined reference to `__sync_sub_and_fetch_4' /tmp/ccC4fGch.o: In function `cmd_logoff': /data/skynet/skynet-src/skynet_server.c:589: undefined reference to `__sync_bool_compare_and_swap_4' /tmp/ccC4fGch.o: In function `cmd_logon': /data/skynet/skynet-src/skynet_server.c:568: undefined reference to `__sync_bool_compare_and_swap_4' /tmp/ccaeanLP.o: In function `reserve_id': /data/skynet/skynet-src/socket_server.c:241: undefined reference to `__sync_add_and_fetch_4' /data/skynet/skynet-src/socket_server.c:247: undefined reference to `__sync_bool_compare_and_swap_2' /data/skynet/skynet-src/socket_server.c:243: undefined reference to `__sync_and_and_fetch_4' /tmp/ccs12kTV.o: In function `get_allocated_field': /data/skynet/skynet-src/malloc_hook.c:36: undefined reference to `__sync_bool_compare_and_swap_4' /data/skynet/skynet-src/malloc_hook.c:40: undefined reference to `__sync_bool_compare_and_swap_4' collect2: ld returned 1 exit status make[1]: *** [skynet] Error 1 make[1]: Leaving directory `/data/skynet' make: *** [linux] Error 2
解决：
这是gcc版本问题，解决方法就是到高版本（如gcc4.5）下载一个linux_atomic.c文件，将其编译为一个静态库链接到你的项目代码，具体做法也比较麻烦。所以，这里推荐重装gcc。
另外，编译skynet建议gcc最低版本4.6.0，可自动下载并更新依赖包。安装gcc过程会比较久，要耐心等待
安装gcc步骤如下：（确保磁盘可用空间至少4G）
wget http://mirrors.ustc.edu.cn/gnu/gcc/gcc-4.6.0/gcc-4.6.0.tar.gz tar -zxf gcc-4.6.0.tar.gz cd gcc-4.6.0 ./contrib/download_prerequisites mkdir build cd build ../configure --prefix=/usr -enable-checking=release -enable-languages=c,c++ -disable-multilib make make install
注意了，要确保 download_prerequisites 安装成功。因为国内连接gnu.org网站不是很稳定，可能出现类似错误：
Resolving gcc.gnu.org... 209.132.180.131 Connecting to gcc.gnu.org|209.132.180.131|:21... connected. Logging in as anonymous ... Logged in! ==> SYST ... done. ==> PWD ... done. ==> TYPE I ... done. ==> CWD /pub/gcc/infrastructure ... done. ==> SIZE mpfr-2.4.2.tar.bz2 ... 1077886 ==> PASV ... couldn't connect to 209.132.180.131 port 10179: Connection refused
如果重试了很多次都无法成功，尝试手动安装吧，主要就3个依赖gmp和mpfr、mpc，装好后再继续执行gcc ../configure及后面的步骤。
wget http://ftp.gnu.org/gnu/gmp/gmp-4.2.2.tar.bz2 tar -jxf gmp-4.2.2.tar.bz2 cd gmp-4.2.2 ./configure --prefix=/usr make && make install wget http://mpfr.loria.fr/mpfr-2.3.2/mpfr-2.3.2.tar.gz tar -zxf mpfr-2.3.2.tar.gz cd mpfr-2.3.2 ./configure --prefix=/usr make && make install wget ftp://gcc.gnu.org/pub/gcc/infrastructure/mpc-0.8.1.tar.gz tar -zxf mpc-0.8.1.tar.gz cd mpc-0.8.1 ./configure --prefix=/usr make && make install
问题7：缺少autoconf
make all PLAT=linux SKYNET_LIBS="-lpthread -lm -ldl -lrt" SHARED="-fPIC --shared" EXPORT="-Wl,-E" MALLOC_STATICLIB="3rd/jemalloc/lib/libjemalloc_pic.a" SKYNET_DEFINES="" make[1]: Entering directory `/data/skynet' cd 3rd/jemalloc && ./autogen.sh --with-jemalloc-prefix=je_ --disable-valgrind autoconf ./autogen.sh: line 5: autoconf: command not found Error 0 in autoconf make[1]: *** [3rd/jemalloc/Makefile] Error 1 make[1]: Leaving directory `/data/skynet' make: *** [linux] Error 2
yum -y install autoconf
ln -sf libjemalloc.so.2 lib/libjemalloc.so ln: creating symbolic link `lib/libjemalloc.so' to `libjemalloc.so.2': Operation not supported make[3]: *** [lib/libjemalloc.so] Error 1 make[3]: Leaving directory `/mnt/hgfs/vm/skynet/3rd/jemalloc' make[2]: *** [3rd/jemalloc/lib/libjemalloc_pic.a] Error 2 make[2]: Leaving directory `/mnt/hgfs/vm/skynet' make[1]: *** [linux] Error 2 make[1]: Leaving directory `/mnt/hgfs/vm/skynet' make: *** [default] Error 2
解决：
虚拟机共享目录不能设置软连接，选择其他目录安装
最后语
如果还遇到其他错误，可以评论一起讨论，正好我也一起整理下。另外，文章看似在总结linux安装skynet遇到的问题，实际上也讨论了lua5.3的安装问题，以及gcc安装问题，希望有所帮助。
