CNI changes (Was: Binary Compatibility)

Mon Aug 4 17:25:00 GMT 2003

Tom Tromey writes:
 > Andrew> Besides, I have some vague memory that Java semantics actually
 > Andrew> require storing into an int field to be atomic. [Looks it
 > Andrew> up.] Oh yes, according to Section 8.3 of the VMspec that
 > Andrew> seems to be the case. But a method pointer might on some
 > Andrew> machines be a long rather than an int, so synchronization may
 > Andrew> be required. I get it now, I think.
 > 
 > I've never even been certain that we correctly implement the java
 > rules for atomicity of stores. These rules are a requirement on us to
 > generate the correct code...
That's right. So why are we making so much fuss about this particular
instance? It's only going to be an issue on a machine that has
multi-word function pointers.
 > Changing the lookup code will make things a little worse. We'll need
 > an extra function call and a synchronization for every JNI method. It
 > would be nice not to do this if possible. This is an area I really
 > don't know much about. Can we tell gcc that we need a certain store
 > to be atomic?
This is all rather system dependent AFAIK.
Andrew.