On Tuesday, 6 November 2012 at 11:27:25 UTC, luka8088 wrote:
Hello everyone,
I was writing some unit tests and I also wanted to test that in
certain cases object references are properly removed everywhere
so that GC can collect them in order to make sure there is no
memory leak. While trying to achieve this I learned that
objects are not always collected at the time I would expect
them to, so I documented current behavior and some tips.
Those are some sample cases which all fit into the general rule:
on collection the stack is scanned and everything that looks like
a pointer to live heap is used to mark heap objects as live, then
the heap objects are scanned and marked transitively. Unmarked
objects get collected. In each case described in the original
post the decision whether some value will be collected or not
depends on whether the local variable is still on the stack and
not overwritten by some newer stack variable. As a consequence:
If it's going to be used later, it's still live on stack.
If it's not going to be used later, it all depends on whether
some other variable defined later is placed by compiler in the
same stack slot, and whether that new variable was initialized
already.
If it was used in a function called and returned, it's not in the
active stack, so it should be collected. And so on.
