lua 1.0 源码分析 -- 1 lua 的虚拟指令

　　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;
end

function 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。