Summary:
The "access path" memory model (equal access paths iff equal object addresses) is suited to when aliasing occurs only at the roots (i.e. variables). When there is intentional aliasing in the middle of an access path, this model will miss the aliasing. For instance if `[x.f] == [y.g]`, then also `[x.f.h] == [y.g.h]`, but the latter access paths are unequal.
In Java, non-static inner classes consistently alias `this.this$0` inside an inner class, which points to the "parent" outer-class object. So if two inner-class objects (belonging to different inner classes) access `this(type:InnerClassA).this$0.f` and `this(type:InnerClassB).this$0.f` the equality will be missed (many other combinations exist). This isn't strictly due to the memory model -- any alias analysis would have to do some class invariant inference to detect this.
For this purpose `AccessPath.inner_class_normalize` exists (it replaces `this.this$0` with `this` of the appropriate type), but this breaks the invariant that we know which formal parameter is at the root (there may not even exist a `this` parameter if the method is static). So this was buggy.
Here we simply recursively remove the synthetic field prefix of the accesses list, while computing forwards the object type. This is only applied when we check aliasing across threads. This will also allow actuals/parameters substitutions (stacked diff) which normalisation was breaking.
Reviewed By: jberdine
Differential Revision: D19601455
fbshipit-source-id: 7e42667b6
Summary:
- Add `Nullsafe` annotation as a general mechanism to specify
type-checking behaviour for nullsafe.
- Document annotation params and provide usage examples with
explanations.
- Add tests to demonstrate the behaviour with different type-checking
modes.
No implementation is added. This diff serves as an RFC to hash out the
details before I dive into code.
Reviewed By: ngorogiannis
Differential Revision: D19578329
fbshipit-source-id: b1a9f6162
Summary: `String.split(regexp)` returns an array that is split by the given regexp. If the regexp doesn't match, the original string is returned. Hence, the resulting array's length must be in `[1, max(1, n_u -1)]` where`n_u` is the upper bound of the string's length.
Reviewed By: dulmarod
Differential Revision: D19578318
fbshipit-source-id: 675af7376
Summary:
In practice, condition redundant is extremely noisy and low-signal
warning (hence it is turned off by default).
This diff does minor tweaks, without the intention to change anything
substantially:
1/ Change severity to advice
2/ Change "is" to "might be"
3/ Describe the reason in case the origin comes from a method.
The short term motivation is to use 3/ for specific use-case: running nullsafe on codebase and
identify most suspicious functions (that are not annotated by often
compared with null).
Reviewed By: artempyanykh
Differential Revision: D19553571
fbshipit-source-id: 2b43ea0af
Summary:
The order by which the scheduler visits odd and even methods here
will determine if there is any report at all. This is a bad test
so remove.
Reviewed By: fgasperij
Differential Revision: D19535537
fbshipit-source-id: 6b64b0de9
Summary:
1. One should use either a writer or a stream to send a response, but not both.
2. A response should be forwarded only if it was commited.
Both properties are extracted from API comments on classes in the servlet API.
Reviewed By: jvillard
Differential Revision: D19514568
fbshipit-source-id: 79f0257ed
Summary:
If data comes from an outer OutputStream, then this outer OutputStream
needs to be flushed before getting the byte array.
Reviewed By: jvillard
Differential Revision: D19514569
fbshipit-source-id: e3e025394
Summary: We were lacking this kind of test where one interface refines the nullability of the other.
Reviewed By: ngorogiannis
Differential Revision: D19514245
fbshipit-source-id: fa3e781f3
Summary:
This is a common enough case to make error message specific.
Also let's ensure it's modelled.
Reviewed By: artempyanykh
Differential Revision: D19431899
fbshipit-source-id: f34459cb3
Summary:
The previous diff changes the message for params case, this one handles
return.
Reviewed By: artempyanykh
Differential Revision: D19430706
fbshipit-source-id: f897f0e56
Summary: Use more informative method names, and add comments explaining the logic behind each test. Correct two cases which are FPs instead of legitimate reports.
Reviewed By: artempyanykh
Differential Revision: D19465227
fbshipit-source-id: 29332e2b9
Summary:
Currently, impurity analysis is oblivious to skipped functions which might e.g. return a non-deterministic value, write to memory or have some other side-effect. This diff fixes that by relying on Pulse's skipped functions to determine impurity. Any unknown function which is not modeled to be pure is assumed to be impure.
This is a heuristic. We could have assumed them to be pure by default as well.
Reviewed By: jvillard
Differential Revision: D19428514
fbshipit-source-id: 82efe04f9
Summary:
As suggested by Ilya, the current message can be improved in a way that
it can contain more clear action. I also added artempyanykh's explanation at the
end of message to provide an additional justification from common sense
perspective.
But most importantly, the previous message was missing a space which is
eye bleeding, how come haven't I noticed this before, I can't stand it
OMG.
Reviewed By: artempyanykh
Differential Revision: D19430271
fbshipit-source-id: dd31f7adb
Summary:
Introduce a new notion of equality for comparing abstract addresses in distinct threads:
```
(** Abstract address for a lock. There are two notions of equality:
- Equality for comparing two addresses within the same thread/process/trace. Under this,
identical globals and identical class objects compare equal. Locks represented by access paths
rooted at method parameters must have equal access paths to compare equal. Paths rooted at
locals are ignored.
- Equality for comparing two addresses in two distinct threads/traces. Globals and class objects
are compared in the same way, but locks represented by access paths rooted at parameters need
only have equal access lists (ie [x.f.g == y.f.g]). This allows demonically aliasing
parameters in *distinct* threads. This relation is used in [may_deadlock]. *)
```
Reviewed By: skcho
Differential Revision: D19347307
fbshipit-source-id: 9f338731b
Summary:
This diff avoids that `array_sizeof` returns bottom value when given Java enum values, which
introduced unreachable code inadvertently.
Reviewed By: ngorogiannis
Differential Revision: D19409077
fbshipit-source-id: 2816fd995
Summary:
The property SkipAfterRemove already had a test, but not for
intra-procedural violations. This adds a test for that case.
Reviewed By: ngorogiannis
Differential Revision: D19330471
fbshipit-source-id: 1dd1c3ad7
Summary: This diff implements this for Field Not Initialized check
Reviewed By: artempyanykh
Differential Revision: D19393989
fbshipit-source-id: cf60e8d53
Summary: add subdirectories so that we can run each java file against its own topl properties
Reviewed By: rgrig
Differential Revision: D19347302
fbshipit-source-id: 562830774
Summary:
This diff does it for nullable dereference and assignment violations
rules which happen under NullsafeStrict case.
Follow up are to make the same for inheritance and field initializer
violations.
Possible follow up includes making error message more specific and
articulare this this is a nullsafe strict mode.
Reviewed By: artempyanykh
Differential Revision: D19392916
fbshipit-source-id: 2554ac7a7
Summary:
Previously, _override resolution_ considered only the number of
arguments. This led to many FPs in nullsafe's _Inconsistent Subclass
Annotation_ check.
Current version also checks that argument types match. However, we
still don't handle type parameters and erasure, so in this sense the
rules are incomplete.
Reviewed By: ngorogiannis, mityal
Differential Revision: D19393201
fbshipit-source-id: a0c75b8dd
Summary:
This diff avoids that null-retuned path's abstract value ruins that of non-null-returned path.
What this diff does is: when joining two abstract states, one is null-return-path and the other is
non-null-return-path (`return obj;`), it keeps the method calls of `obj` from the
non-null-return-path.
While this design is unsound, I think it should work in practice.
Reviewed By: ezgicicek
Differential Revision: D19348313
fbshipit-source-id: cf5d0f3ff
Summary:
Java treats switch on nullables in a non-obvious way (throws an NPE
surprise) so lets have a decidated test exactly for this.
Reviewed By: ngorogiannis
Differential Revision: D19371280
fbshipit-source-id: d9867b6d6
Summary: This diff use actuall call path in the cost results instead of `class name + method name`.
Reviewed By: ngorogiannis
Differential Revision: D19194969
fbshipit-source-id: b72018586
Summary:
Model array length in Java as returning an unknown interval [0, +inf] for now.
Ideally, we can deal with the size in a more precise manner in the future like in InferBo.
Reviewed By: skcho
Differential Revision: D19312123
fbshipit-source-id: 8c51059a4
Summary: Pulse doesn't care about exceptions yet. With Exceptional CFG, java analysis takes a lot of time due to having many disjuncts. Let's use Normal CFG for now.
Reviewed By: jvillard
Differential Revision: D19194479
fbshipit-source-id: f94bb6078
Summary:
In order to improve the impurity analysis, this diff adds models for
- `hasNext()` and - `Object.equals()` modeled as returning a non-deterministic value (havoc_id)
- `next()` modeled as `StdVector.get` with a fresh index
- `iterator` modeled as just returning the underlying list
Reviewed By: jvillard
Differential Revision: D19177392
fbshipit-source-id: 0babb037a
Summary:
This diff updates the relation between iterator (offset) and integer value not only at
assignments (`x += 1`), but also at function calls (`foo()`) that increase integer values by one in
their side effects.
Reviewed By: ezgicicek
Differential Revision: D19163214
fbshipit-source-id: 47e52f939
Summary: This diff extends the domain to express the relation between iterator's offset and integer value.
Reviewed By: ezgicicek
Differential Revision: D19143670
fbshipit-source-id: 6223bc934
Summary:
Old versions of sawja/javalib got the line numbers slightly wrong. The workaround was to do a regexp search in the source file for the right line.
My understanding is that this is no longer necessary. This diff removes it.
Reviewed By: jvillard
Differential Revision: D19033415
fbshipit-source-id: 2da19d66d
Summary:
This is an optimization. We ask the user to tell us which states are nondeterministic, and we
generate code that handle nondeterminism only for those states. It is common for only one state per
TOPL property to be nondeterministic. This speeds up the biabduction-analysis of the monitor by a
factor of ~10. But, using the monitor is only a little faster.
Facebook
Reviewed By: jvillard
Differential Revision: D19160286
fbshipit-source-id: 4dd39769a
Summary:
In the previous code, it removed non-build-called method calls. For example, it was like
```
{non-build-called: {prop1, prop3}}
{build-called: {}}
b.build();
{non-build-called: {}}
{build-called: {prop1, prop3}}
```
However, this behavior introduced a false positive when there is multiple builders that point to the
same abstract object and `build` is called one by one.
This diff changes the semantics to keep the method calls of non-build-called at `build` calls.
Reviewed By: ezgicicek
Differential Revision: D19144525
fbshipit-source-id: e2ace127f
Summary:
This applies some simplifications that were previously
done after footprint (and therefore lost), and some
simplifications that require looking at both pre and
post.
Reviewed By: ngorogiannis
Differential Revision: D19035494
fbshipit-source-id: bad79534a
Summary:
This havocs event data, so that biabduction doesn't try to
track what was the last event processed by the monitor
(which is redundant as long as the state of the monitor
is tracked).
Reviewed By: ngorogiannis
Differential Revision: D19035491
fbshipit-source-id: a1c75daae
Summary:
Don't instrument SIL when we can determine statically that
biabduction symexec would be a no-op.
Reviewed By: ngorogiannis
Differential Revision: D19116849
fbshipit-source-id: 4d25462a3
Summary: It is confusing to report missing props at the the beginning of the method (especially when there are many components created or when the method has many lines). Let's report them at create methods to better contextualize. Also, make the missing prop bold.
Reviewed By: skcho
Differential Revision: D19141135
fbshipit-source-id: a23d2e7c9
Summary:
In addition to
state1 -> state2: pattern
one can now also write
state1 -> state2: pattern if condition
where "condition" is some conjunction of comparisons (==,<,>) that
involve variables bound by "pattern", registers of the automaton, and
constants.
Reviewed By: ngorogiannis
Differential Revision: D19035496
fbshipit-source-id: 6f6e6a9be
Summary:
According to Java semantics, they are always non-null.
Internally they are represented as static fields, so they have
DeclaredNonnull nullability, which means NullsafeStrict mode would
refuse to use them without strictification.
Lets teach nullsafe that these guys are non-nullables.
See also FN in test case.
Reviewed By: ngorogiannis
Differential Revision: D19024547
fbshipit-source-id: 8c120fa50
Summary:
We do not have the create method in the trace which makes it difficult to understand
- inter-procedural issues where create and prop setting are in different methods
- there are multiple create-build chains in a method
Let's add the create to the beginning of the trace. Moreover, let's simplify the prop printing to make traces easier to understand.
Reviewed By: ngorogiannis
Differential Revision: D19020213
fbshipit-source-id: 7f8a5d4ec
Summary: The new domain is much better than the old one. Let's kill the old one (along with old litho tests) and simplify things.
Reviewed By: skcho
Differential Revision: D18959627
fbshipit-source-id: df77ae20e
Summary:
In order to handle the example added:
changed domain of `MethodCalled`
from `CreatedLocation -> (IsBuildCalled X IsChecked X Set(MethodCall))`
to `(CreatedLocation X IsBuildCalled) -> (IsChecked X Set(MethodCall))`
This avoids joining of two method calls where one is build-called and the other is not, e.g.,
```
if(b) {
o.build();
} else {
// no build call
}
```
changed domain of `NewDomain`
from `Created X MethodCalled`
to `(Created X MethodCalled) X (Created X MethodCalled)`
One is for no returned memory and the other is returned memory. This keeps precision some join
points of branches, e.g.,
```
if(b) {
return;
} else {
// no return
}
```
Reviewed By: ezgicicek
Differential Revision: D18909768
fbshipit-source-id: c39d1a1ef
Summary: It is not used anywhere and there are no plans to revive it. Kill it!
Reviewed By: skcho
Differential Revision: D18934719
fbshipit-source-id: b9b069b96
Summary: Guava uses assertions to ensure a future can be gotten without blocking (this means that if the future is not done, the app will crash). This diff teaches the starvation analyser about a number of such assertions, by treating them as assumes (since we don't care about exceptions).
Reviewed By: jvillard
Differential Revision: D18893427
fbshipit-source-id: 4d26a202b
Summary: A future is guaranteed not to block if `isDone()` has returned true first. Add logic for supporting that by remembering the objects that we have called `isDone` on and by making `assume` do the right thing with that knowledge. All this is achieved with the attribute domain.
Reviewed By: ezgicicek
Differential Revision: D18833901
fbshipit-source-id: 7f4ea0cd1
Summary:
When retrieving a value from a container, we previously had an arbitrary hack which would
- In java, give no ownership to the returned object (trying to be sound)
- In C++ give conditional ownership to the current method's first argument (trying to be complete, but doing it badly, as the first argument may not be the `this` object in a static method, or we might be accessing it through another parameter altogether).
Harmonise both by using the existing ownership of the container as ownership value for the returned object (leaning towards completeness).
Reviewed By: jvillard
Differential Revision: D18882800
fbshipit-source-id: f98f8d315
Summary:
This reverts commit 4fd6165d190bab32544f9f040b777565432c15b2.
We don't need to check for reporting each node anymore. It suffices to just check per function.
Reviewed By: skcho
Differential Revision: D18883833
fbshipit-source-id: 2591b3af3
Summary:
Making `MethodCalled` an inverted map from created location to method calls results in not being able to track a builder that is created in two different branches of a conditional with different types. Instead, we can make `MethodCalled` simply a map and also change `Created` to be a map from access paths to a set of created locations.
To deal with the case of setting a prop only in one branch, we need to ensure that whenever we call a create method, we add a binding to `MethodCalled` with an empty list of methods so that its intersection with a non-empty one is empty.
Reviewed By: skcho
Differential Revision: D18883097
fbshipit-source-id: b3464ca20
Summary: As long as the types match, it should be possible to call build on two components that are created at different locations.
Reviewed By: skcho
Differential Revision: D18881740
fbshipit-source-id: 356f9e168
Summary: Add a FN that is detected by the old domain but not the new one
Reviewed By: ngorogiannis
Differential Revision: D18854389
fbshipit-source-id: 9bdc90a6b
Summary: The map from `CreatedLocation` to `MethodCalls` already takes care of the association from create methods to their set props. `MethodCall` comparison should be oblivious the the receiver, otherwise, we risk mistakenly considering two props set at different locations as different.
Reviewed By: skcho
Differential Revision: D18829388
fbshipit-source-id: b5a0d628d
Summary: This diff check and report on every nodes. Problem of the previous design is that it has to report alarms only with the abstract memory of the exit node. However, the new abstract value becomes imprecise at every join points on the path to the exit node, since it is using inverted map, i.e., under-approximation on collecting called methods. As a solution, this diff report on every nodes where `.build` is called with the abstract memory at that node.
Reviewed By: ezgicicek
Differential Revision: D18809449
fbshipit-source-id: 4fd6165d1
Summary: Current method call comparison is too strong. As exemplified with the new test, one can also set the required prop by calling a version which contains the suffixes. The domain should take care of such cases now.
Reviewed By: skcho
Differential Revision: D18808869
fbshipit-source-id: 9f7672e75
Summary: This diff checks litho condition on the new abstract value. This is triggered with `--new-litho-domain`, but it is intra-procedural as of now.
Reviewed By: ezgicicek
Differential Revision: D18783203
fbshipit-source-id: 98570104e
Summary:
Also add logic for recognising excessive timeouts. Refactor the code
around timeouts a little.
Reviewed By: artempyanykh
Differential Revision: D18807836
fbshipit-source-id: df5a1b566
Summary:
`Object.wait()` must be called on a locked monitor and it releases the
lock immediately, as far as other threads are concerned
(it also magically re-takes the lock when the monitor is `notified`).
Starvation can only occur if the UI thread is waiting
a lock that is distinct to that being waited on.
The check present was over-approximate in that it was checking that there exists a lock held by the UI thread and the thread issuing the `wait`, but did not make sure that lock was *not* the one waited on.
Amusingly, the e2e test was correct, but the reporting code wasn't.
Reviewed By: dulmarod
Differential Revision: D18782919
fbshipit-source-id: b3b98239e
Summary: Similar to constructor established attributes, we do the same here for static initializers. That is, attributes of static properties are injected into the initial state of every method.
Reviewed By: ezgicicek
Differential Revision: D18763192
fbshipit-source-id: 3879a27c5
Summary: This diff extends the bound domain to express multiplication of bounds in some simple cases.
Reviewed By: ezgicicek
Differential Revision: D18745246
fbshipit-source-id: 4f2dcb42c
Summary:
One standard way to schedule work is by starting a thread. We treat this by
- Treating invocations of `start` on a receiver with the `Runnable _` attribute as scheduling that runnable for parallel execution in the background (as opposed to on the UI thread).
- If `start` is used on an object of a subclass of `Thread` everything already works thanks to the `get_exp_attributes` function which will implicitly ascribe to an expression the attribute `Runnable _` if the expression points to an object with a known `run` method. This will even take care of some degree of dynamic dispatch, yay!
- If `start` is used on a `Thread` object which has been created with a constructor call provided with a `Runnable` argument, we have to appropriately model that constructor call, which is what is done in `do_call`.
Reviewed By: jvillard
Differential Revision: D18726676
fbshipit-source-id: 0bd83c28e
Summary:
A current blind spot is when object construction stores specific executors / runnables to object fields, which are then never mutated and accessed from normal methods. IOW the attributes established in the constructor are necessary to report properly inside a normal method (assuming these attributes are not invalidated by method code).
To achieve this, first we retain a subset of the final state attributes in the summary (only those that affect instance variables, in constructor methods). Then, when we analyse a non-constructor method:
- we analyse all constructors
- remove all attributes from the attribute map whose key is not an expression of the form `this.x. ...`
- re-localise all remaining keys so that they appear as rooted in the `this` local variable of the current procedure
- join (intersect) all such attribute maps
- use the result in place of initial state as far as the attribute map is concerned for the analysis of the current procedure, which can now start.
This means we can catch idioms that use side-effectful initialisation for configuring certain object fields like executors or runnables.
Reviewed By: jvillard
Differential Revision: D18707890
fbshipit-source-id: 42ac6108f
Summary: Another way to schedule work in android is by posting it to a `Handler`. A handler can be constructed out of the main looper, which forces it to schedule work on the UI thread. To model all this, we add syntactic models for getting the main looper and for creating handlers, and dataflow attributes for tracking that an expression is a looper/the main looper, or a handler constructed out of a looper.
Reviewed By: skcho
Differential Revision: D18706768
fbshipit-source-id: 7c46e6913
Summary:
This gets rid of false positives when something invalid (eg null) is
passed by reference to an initialisation function. Havoc'ing what the
contents of the pointer to results in being optimistic about said
contents in the future.
Also surprisingly gets rid of some FNs (which means it can also
introduce FPs) in the `std::atomic` tests because a path condition
becomes feasible with havoc'ing.
There's a slight refinement possible where we don't havoc pointers to
const but that's more involved and left as future work.
Reviewed By: skcho
Differential Revision: D18726203
fbshipit-source-id: 264b5daeb
Summary:
This diff fixes the model of substring.
Problem: The cost model of the substring function was to return `size of string - start index` as a
cost. However, sometimes this was a negative number, because of state abstractions on paths, array
elements, call contexts, etc, which caused an exception inadvertently.
This diff changes the model to return just `size of string`, when it cannot say `size of string` is
bigger than `start index`.
Reviewed By: ezgicicek
Differential Revision: D18707954
fbshipit-source-id: 63f27e461
Summary:
Instead of trying to figure out what runnable is directly passed to an executor,
use attributes to track the flow of a runnable. This has several advantages:
- Can track runnables across function return values.
- Can somewhat overcome the information loss under dynamic dispatch.
- Unifies handling with other attributes.
Reviewed By: skcho
Differential Revision: D18672676
fbshipit-source-id: a06a0e6ff
Summary:
- Unify treatment of modelled and annotated executors by making things go through attributes.
- Add a return attribute to summaries, so that we can track flows of thread guards/executors/future stuff through returned values.
- Dispatch modeled functions to model summaries.
This will help in following diffs where runnables will also go through attributes.
Reviewed By: skcho
Differential Revision: D18660185
fbshipit-source-id: e26b1083e
Summary: When we see a call to schedule some work on an executor and we don't have evidence that it is on some specific thread (UI/BG), instead of dropping the work, assign it `UnknownThread` and treat it as running on the background by default.
Reviewed By: jvillard
Differential Revision: D18615649
fbshipit-source-id: e8bad64b6
Summary: Following D18351867, this diff adds more size alias: when initial array size is one.
Reviewed By: ezgicicek
Differential Revision: D18530598
fbshipit-source-id: 26d57fe30
Summary:
Now we point to the root cause of the problem, and also provide
actionable way to solve the issue
Reviewed By: artempyanykh
Differential Revision: D18575650
fbshipit-source-id: ba4884fe1
Summary:
Two goals:
1. Be less assertive when speaking about third party code (it might be
written with different conventions).
2. Point to third party signatures folder so the users know how to
proceed
Reviewed By: artempyanykh
Differential Revision: D18571514
fbshipit-source-id: 854d6e746
Summary:
1/ We now support messaging for third-party: show file name and line
number
2/ We did not show information about internal models in case of param
calls
3/ Small change: we don't specify "modelTables.ml" anymore: no need to
expose implementation details
Reviewed By: artempyanykh
Differential Revision: D18569790
fbshipit-source-id: 28586c8ff
Summary:
Whole bunch of changes aimed to make error messages more clear and
concise.
1/ Wording and language is unified. We make errors sound more like a
type system violations, rather than linter reccomendations.
Particularly, we refrain from saying things like "may be null" - this is
a linter-style statement that may provoke discussions (what if the
developer knows it can not be null in this particular case).
Instead, we refer to declared nullability and nullability of actual values. This way, it is more clear that this is not a heuristic, this is how rules of a type-system work.
2/ Additionally, we drop things like field class in places when the
context should be clear by who looks at the error. We expect the user
sees the code and the error caption. So e.g. we don't repeat the word "field"
twice.
3/ In cases when we are able to retrieve formal param name, we include it for
usability.
4/ For Field not initialized error, we refer to Initializer methods:
this is a non-obvious but important nullsafe feature.
Reviewed By: artempyanykh
Differential Revision: D18569762
fbshipit-source-id: 9221d7102
Summary:
It make the message bit less heavy, and also it is kind of obvious that
it is origin.
In follow up diffs we will change the text so it is hopefully even more
obvious.
Reviewed By: artempyanykh
Differential Revision: D18527695
fbshipit-source-id: a305d547b
Summary:
1. We don't want to teach the users to ignore noise origin because
sometimes we are going to render something useful for them.
2. It just looks not cool.
Reviewed By: artempyanykh
Differential Revision: D18527694
fbshipit-source-id: 0ea248122
Summary: Android may spontaneously call these methods on the UI thread, so recognize the fact.
Reviewed By: ezgicicek
Differential Revision: D18530477
fbshipit-source-id: a8a798779
Summary:
First step towards a global analysis. A new command line flag activates the step in `Driver`.
The whole-program analysis is a simple, quadratic (inefficient-as-yet), iteration over all domain elements. However, it is restricted to those elements that are explicitly scheduled to run.
Reviewed By: skcho
Differential Revision: D17787441
fbshipit-source-id: 9fecd766c
Nikos Gorogiannis
Artem Pianykh
Ezgi Çiçek
Jules Villard
Mitya Lyubarskiy
Radu Grigore
Sungkeun Cho