Function prototype declared inside main - best practice?

Question

Is this a good style to have the function prototype declared inside of the main function?

I was looking at a C tutorial, I think is quite out of date. However, they

Answer 1

I'll also say no with the additional reason that if you start using explicit declarations all over the code, you will most definitely get unresolved externals when the function you are calling suddenly changes its signature. If you have ONE declaration in ONE header file, you only need to change ONE declaration when the function changes.

However, I'd say yes because of the following reason: If you are just writing a simple test method that's written for a single use only, i.e. if you want to test something really quick and then discard the function right away. Then it can be nifty to just throw in a declaration right before you want to make the call.

For production code -> No no no ! :)