On Wednesday, 24 January 2018 at 22:27:40 UTC, Nordlöw wrote:
On Wednesday, 24 January 2018 at 21:47:26 UTC, H. S. Teoh wrote:
On Wed, Jan 24, 2018 at 09:48:21PM +0000, Nordlöw via
Digitalmars-d-learn wrote:
Why is the memory overhead for a class instance as high as 3
words (24 bytes on 64-bit systems? I find that annoyingly
much for my knowledge database application.
[...]
There's been an attempt to get rid of the Monitor field, which
takes up one word, but it didn't seem to have gone anywhere
the last time it was discussed. I believe originally it was
always initialized, but lately it seems to have been changed
to be lazily initialized, so at least you'll only incur the
computational cost if you actually use it. Nevertheless, the
field itself is still there.
T
Can I use `*(cast(size_t*)&c.__monitor)` for storing my own
stuff in a class instance `c` if I never use monitors? :)
Maybe, the runtime when destroying that class might think the
monitor is set and try and destroy the mutex it thinks is where
the pointer points to.
BTW: the documentation on the concept of monitors is kind of
sparse here
https://dlang.org/spec/class.html#class_properties
What is the `__monitor` property used for? Something with
synchronized member functions?
It is used for
```
MyClass mc;
synchronized(mc) // <-
{
...
}
```
and I believe synchronized member functions and member functions
of `synchronized class` (which are the same thing really).
The __monitor field points to a mutex object which is managed by
the runtime.
