The assignment operator in C++ returns the value of the assignment to make chaining possible:

int a = b = c = 3;

After this assignment a, b, c will all be equal to 3. This line is also equal to

int a = (b = (c = 3));

In C++ assigning int to bool is made with implicit cast, and

bool b = (x = 3);

will result to 1. Thus the loop condition will always evaluate to true and we get infinite loop.