Summary:
We previously lumped ownership predicates in with all other predicates. That limited us to a flat ownership domain.
This diff separates out the ownership predicates so we can have a richer lattice of predicates with each access path.
This lets us be more precise; for example, we can now show that
```
needToOwnBothParams(Obj o1, Obj o2) {
Obj alias;
if (*) { alias = o1; } else { alias = o2; }
alias.f = ... // both o1 and o2 need to be owned for this to be safe
}
void ownBothParamsOk() {
needToOwnBothParams(new Obj(), new Obj()); // ok, would have complained before
}
```
is safe.
Reviewed By: jberdine
Differential Revision: D5589898
fbshipit-source-id: 9606a46
Summary: Thread-local variables can't be shared between threads, so it's safe to mutate them outside of synchronization
Reviewed By: jeremydubreil
Differential Revision: D4568316
fbshipit-source-id: 0634cad
Summary: This will be important for maintaining ownership of `View`'s, which involve a lot of casting.
Reviewed By: peterogithub
Differential Revision: D4520441
fbshipit-source-id: fdef226
Summary:
Previously, we would lose track of ownership in code like
```
Obj owned = new Obj();
Obj stillOwned = id(owned); // would lose ownership here
stillOwned.f = ... // would report false alarm here
```
This diff partially addresses the problem by adding a notion of "unconditional" (always owned) or "conditional" (owned if some formal at index i is owned) ownership.
Now we can handle simple examples like the one above.
I say "partially" because we still can't handle cases where there are different reasons for conditional ownership, such as
```
oneOrTwo(Obj o1, Obj o2) { if (*) return o1; else return o2; } // we won't understand that this maintains ownership if both formals are owned
Obj stillOwned = oneOrTwo(owned1, owned2);
stillOwned.f = ... // we'll report a false alarm here
```
This can be addressed in the future, but will require slightly more work
Reviewed By: peterogithub
Differential Revision: D4520069
fbshipit-source-id: 99c7418
Summary:
Constants are always "owned" in the sense that no one can mutate them.
In code like
```
Obj getX(boolean b) {
if (b) {
return null;
}
return new Obj();
}
```
, we need to understand this in order to infer that the returned value is owned.
This should fix a few FP's that I've seen.
Reviewed By: peterogithub
Differential Revision: D4485452
fbshipit-source-id: beae15b
Summary:
Previously, we would correctly be silent on code like `x = new T(); x.f = ...`, but would wrongly warn on code like `x = makeT(); x.f = ...`.
The reason is that we only allowed ownership through direct allocation.
This diff adds a boolean that specifies whether the return value is owned as part of the summary.
This allows us to correctly handle many common cases of (transitively) returning a freshly allocated object, but still won't work for understanding that ownership is maintained in examples like
`x = new T(); y = id(x); y.f = ...`.
Reviewed By: jvillard
Differential Revision: D4456864
fbshipit-source-id: b5eec02
Summary:
In code like
```
foo(o) {
iWriteToF(o)
}
```
, the condtional write to `f` in `iWriteToF` should become a conditional write for `foo`.
Reviewed By: peterogithub
Differential Revision: D4429160
fbshipit-source-id: f111ac4
Summary:
In code like
```
foo() {
Object local = new Object();
iWriteToAField(local);
}
```
, we don't want to warn because the object pointed to by `local` is owned by the caller, then ownership is transferred to the callee.
This diff supports this by introducing a notion of "conditional" and "unconditional" writes.
Conditional writes are writes that are rooted in a formal of the current procedure, and they are safe only if the actual bound to that formal is owned at the call site (as in the `foo` example above).
Unconditional writes are rooted in a local, and they are only safe if a lock is held in the caller.
Reviewed By: peterogithub
Differential Revision: D4429131
fbshipit-source-id: 2c6112b
Summary: Just cleanup; gives us slightly less test code to maintain.
Reviewed By: jeremydubreil
Differential Revision: D4429265
fbshipit-source-id: d43c308
Summary:
Maintain an "ownership" set of access paths that hold locally allocated memory that has not escaped.
This memory is owned by the current procedure, so modifying it outside of synchronization is safe.
If an owned access path does escape to another procedure, we remove it from the ownership set.
Reviewed By: peterogithub
Differential Revision: D4320034
fbshipit-source-id: 64f9169
Sam Blackshear
Kyriakos Nikolaos Gkorogiannis
Peter O'Hearn