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version 2.109.0

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Function core.memory.pureCalloc

Pure variants of C's memory allocation functions malloc, calloc, and realloc and deallocation function free.

void* pureCalloc (
  size_t nmemb,
  size_t size
) pure nothrow @nogc @trusted;

UNIX 98 requires that errno be set to ENOMEM upon failure. Purity is achieved by saving and restoring the value of errno, thus behaving as if it were never changed.

See Also

D's rules for purity, which allow for memory allocation under specific circumstances.

Example

ubyte[] fun(size_t n) pure
{
    void* p = pureMalloc(n);
    p !is null || n == 0 || assert(0);
    scope(failure) p = pureRealloc(p, 0);
    p = pureRealloc(p, n *= 2);
    p !is null || n == 0 || assert(0);
    return cast(ubyte[]) p[0 .. n];
}

auto buf = fun(100);
writeln(buf.length); // 200
pureFree(buf.ptr);

Example

Deleting classes 

bool dtorCalled;
class B
{
    int test;
    ~this()
    {
        dtorCalled = true;
    }
}
B b = new B();
B a = b;
b.test = 10;

assert(GC.addrOf(cast(void*) b) != null);
__delete(b);
assert(b is null);
assert(dtorCalled);
writeln(GC.addrOf(cast(void*)b)); // null
// but be careful, a still points to it
assert(a !is null);
assert(GC.addrOf(cast(void*) a) == null); // but not a valid GC pointer

Example

Deleting interfaces 

bool dtorCalled;
interface A
{
    int quack();
}
class B : A
{
    int a;
    int quack()
    {
        a++;
        return a;
    }
    ~this()
    {
        dtorCalled = true;
    }
}
A a = new B();
a.quack();

assert(GC.addrOf(cast(void*) a) != null);
__delete(a);
assert(a is null);
assert(dtorCalled);
writeln(GC.addrOf(cast(void*)a)); // null

Example

Deleting structs 

bool dtorCalled;
struct A
{
    string test;
    ~this()
    {
        dtorCalled = true;
    }
}
auto a = new A("foo");

assert(GC.addrOf(cast(void*) a) != null);
__delete(a);
assert(a is null);
assert(dtorCalled);
writeln(GC.addrOf(cast(void*)a)); // null

// https://issues.dlang.org/show_bug.cgi?id=22779
A *aptr;
__delete(aptr);

Example

Deleting arrays 

int[] a = [1, 2, 3];
auto b = a;

assert(GC.addrOf(b.ptr) != null);
__delete(b);
assert(b is null);
writeln(GC.addrOf(b.ptr)); // null
// but be careful, a still points to it
assert(a !is null);
assert(GC.addrOf(a.ptr) == null); // but not a valid GC pointer

Example

Deleting arrays of structs 

int dtorCalled;
struct A
{
    int a;
    ~this()
    {
        writeln(dtorCalled); // a
        dtorCalled++;
    }
}
auto arr = [A(1), A(2), A(3)];
arr[0].a = 2;
arr[1].a = 1;
arr[2].a = 0;

assert(GC.addrOf(arr.ptr) != null);
__delete(arr);
writeln(dtorCalled); // 3
writeln(GC.addrOf(arr.ptr)); // null

Authors

Sean Kelly, Alex Rønne Petersen

License

Boost License 1.0