Quiz: does this compile or not?
```
class Klass {}
void main() {
immutable Klass klass = new Klass;
synchronized (klass)
{
// do smth
}
}
```
A D object contains two (!) hidden pointers. Two? Yes: the vtable
pointer __vptr, and a pointer to a Monitor struct which contains
a synchronization mutex.
The synchronized statement is lowered into druntime calls that
*write* to __monitor.
Quiz answer: yes it compiles. Oops?
This is related to an earlier discussion on whether TypeInfo
objects should be immutable or not [1]. Should one be able to
synchronize on typeid(...) or not?
```
interface Foo {}
void main() {
synchronized(typeid(Foo)) {
// do smth
}
}
```
Because LDC treats the result of typeid as immutable, the code is
bugged depending on the optimization level.
[1]
http://forum.dlang.org/post/[email protected]
