I'm doing some experiments with ldc2 GC, by instrumenting it and
printing basic information (what is allocated and freed)
My first tests are made on this sample :
```
cat test2.d
import core.memory;
class Bar { int bar; }
class Foo {
this()
{
this.bar = new Bar;
}
Bar bar;
}
void func()
{
Foo f2 = new Foo;
}
int main()
{
Foo f = new Foo;
func();
GC.collect();
return 0;
}
```
When trying to run the instrumented druntime, I get a strange
behavior : the first collection (done with GC.collect) doesn't
sweep anything (in particular, it doesn't sweep memory allocated
in _func()_). The whole sweeping is done when program finish, at
cleanup. I don't understand why : memory allocated in _func()_
shouldn't be accessible from any root at first collection, right ?
```
╰─> /instrumented-ldc2 -g -O0 test2.d --disable-gc2stack
--disable-d-passes --of test2 && ./test2
"--DRT-gcopt=cleanup:collect fork:0 parallel:0 verbose:2"
[test2.d:26] new 'test2.Foo' (24 bytes) => p = 0x7f3a0454d000
[test2.d:10] new 'test2.Bar' (20 bytes) => p = 0x7f3a0454d020
[test2.d:21] new 'test2.Foo' (24 bytes) => p = 0x7f3a0454d040
[test2.d:10] new 'test2.Bar' (20 bytes) => p = 0x7f3a0454d060
============ COLLECTION =============
============= MARKING ==============
marking range: [0x7fff22337a60..0x7fff22339000] (0x15a0)
range: [0x7f3a0454d000..0x7f3a0454d020] (0x20)
range: [0x7f3a0454d040..0x7f3a0454d060] (0x20)
marking range: [0x7f3a0464d720..0x7f3a0464d8b9] (0x199)
marking range: [0x46c610..0x47b3b8] (0xeda8)
============= SWEEPING ==============
=====================================================
============ COLLECTION =============
============= MARKING ==============
marking range: [0x46c610..0x47b3b8] (0xeda8)
============= SWEEPING ==============
Freeing test2.Foo (test2.d:26; 24 bytes)
(0x7f3a0454d000). AGE : 1/2
Freeing test2.Bar (test2.d:10; 20 bytes)
(0x7f3a0454d020). AGE : 1/2
Freeing test2.Foo (test2.d:21; 24 bytes)
(0x7f3a0454d040). AGE : 1/2
Freeing test2.Bar (test2.d:10; 20 bytes)
(0x7f3a0454d060). AGE : 1/2
=====================================================
```
