D is a system programming language and thus allows you to manually manage memory. However, manual memory management is very error-prone and thus D uses a garbage collector by default to free unused memory.
D provides pointer types T* like in C:
int a;
int* b = &a; // b contains address of a
auto c = &a; // c is int* and contains address of a
A new memory block on the heap is allocated using the
new expression, which returns a pointer to the managed
memory:
int* a = new int;
As soon as the memory referenced by a isn't referenced anymore
through any variable in the program, the garbage collector
will free its memory.
D has three different security levels for functions: @system, @trusted, and @safe.
Unless specified otherwise, the default is @system.
@safe is a subset of D that prevents memory bugs by design.
@safe code can only call other @safe or @trusted functions.
Moreover, explicit pointer arithmetic is forbidden in @safe code:
void main() @safe {
int a = 5;
int* p = &a;
int* c = p + 5; // error
}
@trusted functions are manually verified functions that allow a bridge between SafeD and the underlying dirty low-level world.