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.


rdmd playground.d