How to change the function behavior at run-time in luav5.1.4

[刘小凡 <zhqqmao@...>]

Hello, everyone, sometimes I would like to change the run-time behavior of a function, usually I use dofile to achieve, but doing so will not change the previous reference, so I think maybe directly to change the function prototype can be achieved:
I am currently in luaV_settable function to add the following code:

/ * When oldc and valc are the type of closure lua * /
oldc-> l.p = valc-> l.p;


However, sometimes the program crashes, I would like to know where I ignored, Thank you.