a double free error stemming from set::erase

I keep getting the runtime error double free or corruption (!prev). I've spent a while trying things out, and I think I can come up with smaller reproducible example.

This code produces a similar "double free" error. What's going on here? I thought set::erase increments the iterator.

#include <iostream>
#include <set>
#include <string>

int main() {

    std::set<int> tmp = {1,2,3};
    for(auto num = tmp.begin(); num != tmp.end(); ) {
        if(true) {
            std::cout << "removing...\n";
            tmp.erase(num);
        }
    }

    return 0;
}