On 06/21/2017 07:23 PM, H. S. Teoh via Digitalmars-d-learn wrote:
Being a systems programming language means you should be able to do things outside the type system (in @system code, of course, not in @safe code), including storing pointers as int values. Any C code that your D program interoperates with may also potentially do similar things.
The GC doesn't scan the C heap. You didn't say that it does, but it might be understood that way.
Because of this, the GC cannot simply assume that an int value isn't actually a pointer value in disguise, so if that int value happens to coincide with an address of an allocated memory block, the only sane thing it can do is to assume the worst and assume that the memory is still live (via that (assumed) reference).
There are cases where the GC does assume that ints are not pointers. For example, an int[] on the GC heap won't be scanned for pointers. The GC is neither completely precise nor completely conservative.
