Write C++ char array without branching (II)

#include <iostream>
        char*         a = "abcdef";
        unsigned int  i = 0;
        unsigned int  k = 1;            // k to be determined

int main() {
        start:
            int b = (unsigned int)a[i] == 0;
            __asm__ ("jmp b*k");
        print:
            std::cout << a[i++];
            goto start;
        exit:
            std::cout << "\n";
            return 0;
}