Whether a description appears or not, that does not mean a thing.
After a trace instruction the variable trace_hit is 1 (something hit) or 0 (else), it is not set to different values than 1/0.
Have a look at the following example:

function a_useless_function {
// ...
return 523;
}


...
result = a_useless_function();
Now result is 523 and no predefined variable has been changed to return the value.
It is exactly the same with c_trace:
result = c_trace(some parameters);
or
var distance;
distance = c_trace(some parameters);.