On Saturday, 29 July 2017 at 20:44:30 UTC, Johan Engelen wrote:
I'd like to check a bit of info I need for Address Sanitizer
checking.
The spec says [1]:
Use the destroy function to finalize an object by calling its
destructor. The memory of the object is not immediately
deallocated, instead the GC will collect the memory of the
object at an undetermined point after finalization:
```
class Foo { int x; this() { x = 1; } }
Foo foo = new Foo;
destroy(foo);
assert(foo.x == int.init); // object is still accessible
```
This tells me 2 things that I'd like to verify:
1. The destroyed memory is set to the type's `.init` value.
(but the Ctor is not called)
2. It is _valid_ to access the memory after calling destroy.
Point 2 is worrying: what if there is a thread switch right
after destroy, in which a GC collect happens?
Thanks,
Johan
[1] https://dlang.org/spec/class.html#deallocators
For 1) look at rt_finalize2 in rt/lifetime.d*. It is the function
called by destroy. It sets the class to its init value:
auto w = (*pc).initializer;
p[0 .. w.length] = w[];
So it will memcpy Foo.initializer into foo.
For 2) I think you're right, it seems to be unsafe to access the
object after destroying.
*
https://github.com/dlang/druntime/blob/3485ff859a29ba44e7949bc49e62d5dd3a2a9ff0/src/rt/lifetime.d#L1402
