只要堆栈保持平衡，是否可以修改堆栈值? [英] Is it allowed to modify stack values as long as the stack stays balanced?

问题描述

每个人都知道保持堆栈平衡是一种良好的编程习惯.我想知道的是，是否允许我在从Lua脚本调用的C函数中修改堆栈值?考虑以下代码:

Everybody knows it is good programming practice to keep the stack balanced. What I'm wondering, though, is whether I'm allowed to modify stack values in a C function called from a Lua script? Consider the following code:

int myfunc(lua_State *L)
{
    int arg1 = luaL_checkinteger(L, 1);
    int arg2 = luaL_checkinteger(L, 2);

    // pop arg 2
    lua_pop(L, 1);

    // this is to be our return value
    lua_newtable(L);

    ...do complicated stuff...

    // restore second parameter but set it to nil for convenience's sake
    lua_pushnil(L);
    lua_insert(L, 2);

    // return our table
    return 1;
}

因此，上面的代码将第二个参数替换为nil.这是允许的还是我必须恢复原始值，即我必须做

So the code above replaces the second parameter with nil. Is this allowed or do I have to restore the original value, i.e. would I have to do

lua_pushinteger(L, arg2);

代替

lua_pushnil(L);

?还是只要myfunc在堆栈平衡的情况下返回就没关系吗?

? Or doesn't this matter as long as myfunc returns with the stack balanced?

推荐答案

堆栈值是被调用的C函数的属性.您可以与他们一起做任何您想做的事情.外部的唯一影响是该函数返回的值.

The stack values are the property of the C function being called. You can do whatever you wish with them. The only effect to the outside is the values returned by the function.

C函数不需要保持堆栈平衡，也就是说，其内容或条目数量与进入时相同.

C functions called from Lua do not need to keep the stack balanced, that is, with the same contents or number of items it had on entry.

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