It would be a little more accurate to say that in D, memory safety is optional. If you wrote every method using the @safe flag, you'd be forced to write a memo

It would be a little more accurate to say that in D, memory safety is optional. If you wrote every method using the @safe flag, you'd be forced to write a memory-safe program. Eg: void main() @safe { int everything = 42; int* theAnswer = &a; int* earth = theAnswer * 2; // Won't compile. } With no flag or @system, safety is not ensured. Using @trusted will allow a function to be called, safe or not, from other safe functions ending the safety. But by design @safe functions can only call other @safe functions.