lua的解释器拿到 lua 编写的源码，首先进行解析，就是进行词法分析和语法分析，将源码转换成 lua 的指令集，然后执行这个指令集。

　　

　　lua 源码：

　　

function f(val)    return val;endfunction main()    local i = 1;    local j = 2;    local b = i + f(2);    --local b = i + j;    print("retval = "..b);    return b;end

　　　调用 main 的指令集分析：

　　

in while  opcode = [CALLFUNC]. -- main in while  opcode = [NOP]. in while  opcode = [SETFUNCTION]. in while  opcode = [ADJUST]. in while  opcode = [NOP]. in while  opcode = [SETLINE]. in while  opcode = [PUSH1].  -- i  in while  opcode = [SETLINE]. in while  opcode = [PUSH2].  -- j in while  opcode = [SETLINE].  -- local b = i + f(2) in while  opcode = [PUSHLOCAL0]. -- i in while  opcode = [PUSHGLOBAL]. -- f in while  opcode = [PUSHMARK]. in while  opcode = [PUSH2].    -- val in while  opcode = [CALLFUNC]. -- f() in while  opcode = [NOP]. in while  opcode = [SETFUNCTION]. in while  opcode = [ADJUST]. in while  opcode = [NOP]. in while  opcode = [SETLINE]. in while  opcode = [PUSHLOCAL0]. -- val  in while  opcode = [RESET]. in while  opcode = [RETCODE]. in while  opcode = [SETLINE]. in while  opcode = [ADJUST]. in while  opcode = [ADDOP].  -- local b = i + f(2) in while  opcode = [SETLINE]. in while  opcode = [NOP]. in while  opcode = [PUSHGLOBAL]. --  print in while  opcode = [PUSHMARK]. in while  opcode = [PUSHSTRING]. -- retval = in while  opcode = [PUSHLOCAL2]. -- b in while  opcode = [CONCOP]. in while  opcode = [CALLFUNC]. -- print()retval = 3 in while  opcode = [ADJUST]. in while  opcode = [SETLINE]. in while  opcode = [PUSHLOCAL2]. in while  opcode = [RESET]. in while  opcode = [RETCODE]. in while  opcode = [HALT].

 PS:

　　函数就是一个入口地址，入口是通向将要执行的指令集。想下 汇编 中的 call，ret。lua 中的虚拟指令类似，只不过入口中的指令集是 lua 自己的虚拟指令，不是像 c 那样的机器指令。