skynet是爲在線遊戲服務器打造的輕量級框架，使用c+lua實現，支持linux 。使用這套框架能獲得很大收益，其中一個就是，基本只需要用lua開發，很少用到c，提高了開發效率。但是，skynet本身對系統有很大依賴性，安裝說明過於簡單，沒有提及到。所以文章這裏總結linux安裝skynet問題，希望有所幫助。
skynet的安裝過程
git clone https://github.com/cloudwu/skynet.git
cd skynet
make linux
簡單3步，對於很多高版本的系統來說，可能就這3步。但是，低版本系統可能無法安裝，如下：
1. gcc版本問題
2. 缺少 readline
3. 缺少 ncurses
4. 缺少 git （非必要項，則要手動下載skynet及3rd下的jemalloc）
5. 缺少 autoconf
所以，這裏以CentOS5.5系統做說明，這系統不具備以上幾個條件，甚至連git都無法通過包管理來安裝。在skynet的編譯過程中，如果在make步驟出現錯誤，要用 make cleanall 清除已編譯的文件，不然會出現莫名其妙的錯誤。
在早期的skynet版本，lua不能清除乾淨，若是這樣，執行：cd 3rd/lua && make clean && cd -
問題1：缺少git
# git clone https://github.com/cloudwu/skynet.git
bash: git: command not found
解決：
這裏要安裝git，在安裝git過程中，非常重要一步是安裝curl，而這一步會把git所有的依賴裝上，如curl和openssl，而git編譯時也要找到curl庫
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
問題2：git https錯誤
# git clone https://github.com/cloudwu/skynet.git
Cloning into 'skynet'...
fatal: Unable to find remote helper for 'https'
解決：
很多網友都是說把https換成git解決，但也只是暫時性的。報錯是git安裝時系統缺少curl導致的，參考問題1重裝git
重裝git後，如果還不行，應該是git軟連接問題，如下修正：
ln -sf /usr/bin/git /bin/git
問題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
解決：
yum -y install readline-devel
問題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
解決：
很多網友說修改Makefile，在SYSLIBS變量中追加” -lncurses “選項，但這樣不方便，以後還會遇到這個問題。所以這裏建議手動安裝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
備註：
1、國內連接gnu.org網站不是很穩定，可能wget要多試幾次。
2、通過ldconfig -p |grep readline可以測試readline的庫是否成功加載
3、如果還無法解決，執行以下命令（建議先備份下）：
rm -rf /usr/lib/libreadline*
ldconfig
如果是64位機器：
rm -rf /usr/lib64/libreadline*
ldconfig
問題5：lua整數編譯報錯
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
解決：
這個是skynet最常見的編譯失敗了，和gcc版本有關，升級gcc可以解決問題。
最簡單的方法：修改Makefile，在CFLAGS 加入 -std=gnu99
如果不想手動改，可用以下命令：
sed -i "s|CFLAGS =|CFLAGS = -std=gnu99 |" Makefile
如果是升級gcc參考問題6的解決方式。
問題6：gcc編譯器問題
/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
解決：
這是gcc版本問題，解決方法就是到高版本（如gcc4.5）下載一個linux_atomic.c文件，將其編譯爲一個靜態庫鏈接到你的項目代碼，具體做法也比較麻煩。所以，這裏推薦重裝gcc。
另外，編譯skynet建議gcc最低版本4.6.0，可自動下載並更新依賴包。安裝gcc過程會比較久，要耐心等待
安裝gcc步驟如下：（確保磁盤可用空間至少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，要確保 download_prerequisites 安裝成功。因爲國內連接gnu.org網站不是很穩定，可能出現類似錯誤：
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
如果重試了很多次都無法成功，嘗試手動安裝吧，主要就3個依賴gmp和mpfr、mpc，裝好後再繼續執行gcc ../configure及後面的步驟。
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
問題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
解決：
yum -y install autoconf
問題8：鏈接錯誤
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
解決：
虛擬機共享目錄不能設置軟連接，選擇其他目錄安裝
最後語
如果還遇到其他錯誤，可以評論一起討論，正好我也一起整理下。另外，文章看似在總結linux安裝skynet遇到的問題，實際上也討論了lua5.3的安裝問題，以及gcc安裝問題，希望有所幫助。