Hoisting in Ansi-C?

Question

In JavaScript I can do something like this:
console.log(hi());
function hi(){ return "hello" }

So you can call the function before declaration because of the engines hoisting system.

Here I saw, that this feature in C also work.
printf("%d", sum(3,4));
int sum(int a, int b){
return a+=b;
}
So C is use hoisting?

Answer 1

C is a compiled language. Your code can reference external functions, but they are linked in a separate linker stage after all files are compiled.
The code you provided can be compiled by the ancient K&R dialect of C.
K&R C assumes that any function encountered without a prior declaration, returns an int.
No error checking is done on the parameters you pass to the function, so they better match what the actual function expects.

EDIT: The subject line says ANSI C, but I'm pretty sure this code would trigger warning on any respectable ANSI C compiler.

EDIT 2:
According to code playground, ANSI C accepts your code without any warnings. It simply does an implicit declaration of any new function as returning an int.