Debugger hangs on Float instruction

When I run this code on my STM32L1 board, the debugger hangs once it reaches to a Float (in this case the variable 'Distance') or Delay, I mean it seems like it's processing, however it never goes through, and I have to close it and run the debugger again, which hangs of course again. Note that the code builds without errors or warnings.
Is there's any special configuration for float ?

The following is the related part of the code:

void Delay(int x){
    //input milliseconds, delay that number of milliseconds
    int a,b;
    for(a=0; a<x; a++){
        for(b=0; b<1000; b++){
        }
    }
}
                .
                .
                .

volatile int timespan = 0;                      // Total pulse width

int main(void){

                float Distance;     // actual distance in cm
                .
                .
                .

    while(1){

        TIM4_Echo_Read();

    Distance = (timespan / 58.0);

        if (Distance <= 100){

            GPIOB->BSRRL = (1<<7);
        }
            else {
            GPIOB->BSRRH = (1<<7);

            }
                Delay(10);
        }

timespan is declared as a global int.
Note that none of this happens when I declare Distance as int instead of float.

Any idea why the debugger keeps getting stuck on float instructions?