Summary:
In some cases the result of an integer conversion needs to be
truncated by a bit.
Differential Revision: D18271179
fbshipit-source-id: e80740045
Summary:
This diff tries to make less imprecise division by constants results.
For example, the results of the division `[l, u] / c`, where `c` is a positive constant, are:
1. If `l/c` or `u/c` is representable in the bound domain, it uses the precise bounds, i.e., `[l/c, u/c]`.
2. If it is not representable, it tries to make conservative results:
if `0<=l<=u`, it returns `[0, u]` because `0 <= [l/c, u/c] <= u`
if `l<=u<=0`, it returns `[l, 0]` because `l <= [l/c, u/c] <= 0`
if `l<=0<=u`, it returns `[l, u]` because `l <= [l/c, u/c] <= u`
3. otherwise, it returns top, `[-oo, +oo]`
Reviewed By: ezgicicek
Differential Revision: D18270380
fbshipit-source-id: 8fb14c0e4
Summary:
Add precision to analysis by elaborating the thread-status domain. This is done by having unknown (bottom), UI, BG or Any (both/top) elements in the lattice. This way, when we branch on thread-identity (if I am on UI thread do this, otherwise do that), we know that in one branch we are on UI thread and on the other we are *not* on the UI thread (BG thread), where previously the other branch would just go to top.
With this knowledge we can throw away pairs that come from callees which run on a thread that is impossible, given the current caller thread identity. This can happen when annotations are used incorrectly, and since this is the purview of annot-reachability, we just drop those pairs entirely.
Reviewed By: skcho
Differential Revision: D18202175
fbshipit-source-id: be604054e
Summary:
Improve the invariants to show that phi instructions are correctly
translated. It remains to show that the invariants can be established
when jumping to the start of a block
Reviewed By: jberdine
Differential Revision: D18228272
fbshipit-source-id: 4330b4781
Summary:
Now that we have two similar functions, it becomes confusing, because `Pp.to_string` and `Pp.string_of_pp` can seem to do the same stuff, while in reality they do the opposite.
Well, it is still bit confusing, because the proper names would be
`Pp.pp_of_to_string` and `Pp.to_string_of_pp`, but I think this high
level order names are not necessary given that in most cases they will
be used as concrete functions.
I think `Pp.of_string` captures such usages better than `to_string` used to do: you need to pp stuff,
but you have a string (or, technically, a function that returns a string), so you pretty print OF that string, aren't you?
Reviewed By: jvillard
Differential Revision: D18245876
fbshipit-source-id: fd4b6ab68
Summary:
This is a helper module for reading info from a 3rd party nullability repository.
Next diffs are going to use it for reading nullability repository from
disk.
Reviewed By: artempyanykh
Differential Revision: D18225473
fbshipit-source-id: 06a2dc97e
Summary:
We see failures in the Travis CI which may be related to known issues in earlier versions of mlgmpidl.
Facebook
Reviewed By: jvillard
Differential Revision: D18244267
fbshipit-source-id: 9889c9c86
Summary:
Steal a page from RacerD (and improve interface of) on using certain calls to assert
execution on a particular thread. Reduces FPs and FNs too.
Reviewed By: dulmarod
Differential Revision: D18199843
fbshipit-source-id: 5bdff0dfe
Summary:
The zero cost of node does not make sense especially when the abstract memory is non-bottom. This
resulted in unreasonable zero cost results sometimes, e.g. when the checker could not find
appropriate control varaibles having interval values of iteration. This diff fixes this, so sets
the minimum basic cost as 1, if the abstract memory at the node is non-bottom.
Reviewed By: ezgicicek
Differential Revision: D18199291
fbshipit-source-id: b215d10e5
Summary:
When reporting null dereference it is useful to know where the null came
from.
Reviewed By: skcho
Differential Revision: D18206459
fbshipit-source-id: 0c8e6781b
Summary:
This simplifies the code overall. It also makes accessing the action of
a "trace" (which is now stored alongside it instead of deep inside it)
constant time instead of linear in the number of nested calls.
Reviewed By: skcho
Differential Revision: D18206460
fbshipit-source-id: 9546ff36f
Summary:
This adds a more interesting value domain to pulse: concrete intervals.
There are still two main limitations:
1. arithmetic operations are all over-approximated: any assignment involving arithmetic operations is replaced by non-determinism
2. abstract values that are discovered to be equal are not merged into one
Reviewed By: skcho
Differential Revision: D18058972
fbshipit-source-id: 0492a590f
Summary:
This does several things because it was hard to split it more:
1. Split most of the arithmetic reasoning to PulseArithmetic.ml. This
doesn't need to be reviewed thoroughly because an upcoming diff
changes the domain from just `EqualTo of Const.t` to an interval domain!
2. When going through a prune node intra-procedurally, abduce arithmetic
facts to the pre (instead of just propagating them). This is the "assume
as assert" trick used by biabduction 1.0 too and allows to propagate
arithmetic constraints to callers.
3. Use 2 when applying summaries by pruning specs whose preconditions
have un-satisfiable arithmetic constraints.
This changes one of the tests! Pulse now does a bit more work to find
the false positive, as can be seen in the longer trace.
Reviewed By: skcho
Differential Revision: D18117160
fbshipit-source-id: af3b2c8c0
Summary:
Instead of checking that each address in the pre that must be valid is
not invalid in the caller (and error out if it turns out it is invalid)
as we discover them, save these checks for after we are sure that the
precondition can be applied. It is in fact a bug that we can report an
error when trying to apply a precondition that is actually not
satisfiable in the current state for other reasons than lifetime issues.
We still want to skip calls in case of weird issues like mismatch in
number of formals vs actuals.
This will have more obvious effects later when we also check that
arithmetic facts in preconditions are satisfied at the call site: if a
pre mandates "x=1" and "y must be valid" and we have "x=0" and "y
invalid" then we shouldn't report an error.
Reviewed By: skcho
Differential Revision: D18115229
fbshipit-source-id: ad4ce72ff
Summary:
If a precondition cannot be applied, it means that this program path
somehow doesn't make sense for the caller and so should be pruned. Right
now we just treat this as skipping over the call instead.
This will become more important when specs start mentioning arithmetic
facts that must be satisfied at the call site. As it is we will only
stop if we discover aliasing in the pre not present at the call site or
vice versa.
Reviewed By: dulmarod
Differential Revision: D18115230
fbshipit-source-id: 4f1c7a583
Summary: The way `<=` is used in `AbstractDomain` prevents infix use and forces bracketing it everywhere. Replace with simple `leq`.
Reviewed By: jvillard
Differential Revision: D18201854
fbshipit-source-id: 8175224e4
Summary:
Add a new interval abstract domain. This domain uses the APRON
numerical analysis library to keep track of the range of values held
by llair variables where possible. This works by translating LLAIR
expressions into APRON tree expressions, so only handles the
subset of the LLAIR expression language that can be embedded.
Note also that function summarization is not yet implemented.
Future commits will add summarization and improve coverage of
LLAIR's expression language.
Reviewed By: jberdine
Differential Revision: D17763517
fbshipit-source-id: 826ce4cc5
Summary: Abstract state tracks stuff that is not needed for summaries, wasting space/time.
Reviewed By: jvillard
Differential Revision: D18171499
fbshipit-source-id: 25483ced9
Summary:
Primitive types are not annotated. Because of that, we used to implicitly derive
`DeclaredNonnull` type for them. This worked fine, but this leads to errors in Strict mode, which does
not believe DeclaredNonnull type.
Now lets offifically teach nullsafe that primitive types are
non-nullable.
Reviewed By: jvillard
Differential Revision: D18114623
fbshipit-source-id: 227217931
Summary:
This diff adds SafeInvertedMap, which is similar to InvertedMap but it
guarantees that there is no top elements in the tree of the map.
Reviewed By: ezgicicek
Differential Revision: D18062174
fbshipit-source-id: 2fbc51f31
Summary: `Str.regexp_string` should be used to find a method name instead of `Str.regexp`.
Reviewed By: ezgicicek
Differential Revision: D18136598
fbshipit-source-id: c4b56dd64
Summary:
The reporting phase would go through the critical pairs in the summary roughly three times, once for each major type of warning (starvation, lockless violation, deadlock). This is wasteful, and also led to some code duplication. Fix.
Also, use the more efficient annotation matcher in `ConcurrencyModels` and move some model matchers to `StarvationModels`.
Reviewed By: artempyanykh
Differential Revision: D18118149
fbshipit-source-id: ff4dc3d07
Summary: It is now possible to push the thread status into each critical pair. This leads to higher precision, because when code branches on whether it is on the UI thread, the final abstract state of the procedure will be `AnyThread`, but pairs created in the UI thread branch should know that their status is `UIThread`, not `AnyThread`.
Reviewed By: jvillard
Differential Revision: D18114273
fbshipit-source-id: cbb99b46f
Summary: This will be more useful later when adding another one.
Reviewed By: ezgicicek, jberdine
Differential Revision: D18115231
fbshipit-source-id: a0a01901a
Summary:
The business of translating `Top/True/False` to `true/false` can be
hidden more.
Reviewed By: skcho
Differential Revision: D18115228
fbshipit-source-id: 071fcbddf
Summary:
Warning 33 (unused open) is enabled but the module open is not really
unused, it's just also opened at the top of the file...
Reviewed By: skcho
Differential Revision: D18114385
fbshipit-source-id: 2a8f9512a
Summary:
This diff avoids making top values on unknown non-static function,
such as abstract function, calls. This is necessary because the
generated top values ruin the precision of the cost checker.
Reviewed By: ezgicicek
Differential Revision: D17418611
fbshipit-source-id: aeb759bdd
Summary:
The wrong function was used when we tried to see if the class is
annotated with NullsafeStrict. This made it work only for non-static
methods.
Now we use the proper way.
Reviewed By: ngorogiannis
Differential Revision: D18113848
fbshipit-source-id: 02b7555be
Summary:
Previously, we considered a function which modifies its parameters to be impure even though it might not be modifying the underlying value. This resulted in FPs like the following program in Java:
```
void fresh_pure(int[] a) {
a = new int[1];
}
```
Similarly, in C++, we considered the following program as impure because it was writing to `s`:
```
Simple* reassign_pure(Simple* s) {
s = new Simple{2};
return s;
}
```
This diff fixes that issue by starting the check for address equivalnce in pre-post not directly from the addresses of the stack variables, but from the addresses pointed to by these stack variables. That means, we only consider things to be impure if the actual values pointed by the parameters change.
Reviewed By: skcho
Differential Revision: D18113846
fbshipit-source-id: 3d7c712f3
Summary:
Add some theorems establishing the correspondence between the
implementation of the Convert operation in OCaml and the definition of
Convert in the semantics. Essentially, the OCaml version is in terms of
extracting certain ranges of bits, whereas the semantics is in terms of
integer arithmetic (addition, modulus, and exponentiation)
Reviewed By: jberdine
Differential Revision: D18113878
fbshipit-source-id: c318596d0
Summary:
This commit adds truncation, sign extension and zero extension to LLVM
and the Convert instruction to LLAIR.
The LLVM instructions use HOL's build-in word/int and word/num
conversions. Sanity-checking theorems prove that zero-extending leaves
the value of the word unchanged when considered as an unsigned value,
and that sign-extending leaves the value unchanged when considered as a
signed value.
The llair semantics for Convert uses the truncate_2comp function which
converts an integer to another integer as though they were represented
in 2's complement. e.g. truncate_2comp 255 16 = 255, truncate_2comp
255 8 = -1, truncate_2comp -3 2 = 1
Reviewed By: jberdine
Differential Revision: D18058833
fbshipit-source-id: df9de480c
Summary:
The old syntactic invariant in prog_ok was in the wrong direction,
saying that all labels in a phi instruction have to exist, rather than
saying that when we jump to a new block, the label of the block we came
from must be in all of the phi instructions.
Reviewed By: jberdine
Differential Revision: D18058832
fbshipit-source-id: d2ad33b04
Summary:
This required some minor tweaks to how the semantics encode values into
and out of byte lists. The remaining problems have to do with how LLVM
globals are translated into llair. At the moment, llair semantic's state
keeps a mapping for globals to their addresses, following the LLVM
semantics. However, it is not used because the translation (following
the code in frontend.ml) translates LLVM globals into llair locals,
which the llair semantics isn't set up to handle.
Reviewed By: jberdine
Differential Revision: D17930787
fbshipit-source-id: 06c6368e0
Summary: As suggested by artempyanykh, this will make it bit more clear
Reviewed By: artempyanykh
Differential Revision: D18037204
fbshipit-source-id: 65cb96815
Summary: We stop tracking at builder boundaries. Let's tract create methods as well so that trace is more informative.
Reviewed By: skcho
Differential Revision: D18038637
fbshipit-source-id: a99b6431f
Summary:
Although, we have Makefile and BUCK build def, this is a maven project
which is supposed to be released to Maven Central, so it's worth
having a short instruction on how to build it with maven.
Reviewed By: mityal
Differential Revision: D18037109
fbshipit-source-id: 6aebf4384
Summary: Adding support to matching block names. We match mangled block names. We also needed to extend the function for extracting the range for each method, to also traverse the stmts to be able to find the block declarations.
Reviewed By: skcho
Differential Revision: D17956931
fbshipit-source-id: 707908812
Sungkeun Cho
Josh Berdine
Scott Owens
Nikos Gorogiannis
Mitya Lyubarskiy
Dulma Churchill
Jules Villard
Martin Trojer
Benno Stein
Ezgi Çiçek
Artem Pianykh