Is there a built-in way to swap two variables in C

There is no equivalent in C - in fact there can't be, as C doesn't have template functions. You will have to write separate functions for all the types you want to swap.

You need to define it yourself.

1. C doesn't have templates.

2. If such function does exist it would look like void swap(void* a, void* b, size_t length), but unlike std::swap, it's not type-safe.

3. And there's no hint such function could be inlined, which is important if swapping is frequent (in C99 there's inline keyword).

4. We could also define a macro like

    #define SWAP(a,b,type) {type ttttttttt=a;a=b;b=ttttttttt;}
   

   but it shadows the ttttttttt variable, and you need to repeat the type of a. (In gcc there's typeof(a) to solve this, but you still cannot SWAP(ttttttttt,anything_else);.)

5. And writing a swap in place isn't that difficult either — it's just 3 simple lines of code!