（原+译）LUA调用C函数

转载请注明出处：

http://www.cnblogs.com/darkknightzh/p/5804924.html

原始网址：

http://www.troubleshooters.com/codecorn/lua/lua_lua_calls_c.htm

1. 新建hellofunc.c，输入：

/* hellofunc.c (C) 2011 by Steve Litt
 * gcc -Wall -shared -fPIC -o Cfunc.so -I/usr/include/lua5.1 -llua5.1 hellofunc.c
 * Note the word " Cfunc " matches the string after the underscore in
 * function luaopen_ Cfunc(). This is a must.
 * The -shared arg lets it compile to .so format.
 * The -fPIC is for certain situations and harmless in others.
 * On your computer, the -I and -l args will probably be different.
*/

#include <lua5.1/lua.h>                               /* Always include this */
#include <lua5.1/lauxlib.h>                           /* Always include this */
#include <lua5.1/lualib.h>                            /* Always include this */

static int isquare(lua_State *L)               /* Internal name of func */
{              
    float rtrn = lua_tonumber(L, -1);      /* Get the single number arg */
    printf("Top of square(), nbr=%f\n",rtrn);
    lua_pushnumber(L,rtrn*rtrn);           /* Push the return */
    return 1;                              /* One return value */
}
static int icube(lua_State *L){                /* Internal name of func */
    float rtrn = lua_tonumber(L, -1);      /* Get the single number arg */
    printf("Top of cube(), number=%f\n",rtrn);
    lua_pushnumber(L,rtrn*rtrn*rtrn);      /* Push the return */
    return 1;                              /* One return value */
}


/* Register this file's functions with the
 * luaopen_libraryname() function, where libraryname
 * is the name of the compiled .so output. In other words
 * it's the filename (but not extension) after the -o
 * in the cc command.
 *
 * So for instance, if your cc command has -o power.so then
 * this function would be called luaopen_power().
 *
 * This function should contain lua_register() commands for
 * each function you want available from Lua.
 *
*/
int luaopen_Cfunc(lua_State *L){
    lua_register(
            L,               /* Lua state variable */
            "testsquare",        /* func name as known in Lua */
            isquare          /* func name in this file */
            );  
    lua_register(L,"testcube",icube);
    return 0;
}

2. 在ubuntu的终端中生成.so：

gcc -Wall -shared -fPIC -o Cfunc.so hellofunc.c

说明：luaopen_ XXX对应于上面-o后面的XXX.so的XXX。供LUA代码中require“XXX”来调用。

3. 新建myLUA.lua，输入：

require("Cfunc")
print(testsquare(1.414213598))
print(testcube(5))

4. 终端中输入:

lua myLUA.lua

5. 结果：

说明：电脑上装了lua5.1和lua5.2.默认的是lua5.2.使用lua myLUA.lua后，提示：

经过查找，发现默认的是lua5.2。然后直接使用lua5.1 myLUA.lua后，显示的就是正确的结果（如果使用lua5.2 myLUA.lua，显示的就是上面的错误）。当然，如果装了torch，torch默认的也是5.1的话，使用th myLUA.lua后，也能显示正确的结果，如下：