Summary:
This makes sure we call `AbductiveDomain.summary_of_post` exactly once
per post-condition. Notice in particular in the diff:
- in Pulse.ml we remove a now-certified-useless "is_unsat_expensive"
call
- in PulseOperations.ml we add a previously-missing call to
`summary_of_post` (it's needed to remove local variables from the
symbolic state + normalize)
The price to pay is ugly type annotations and down-casting peppered in a
few places, in reasonable number.
Reviewed By: da319
Differential Revision: D24078564
fbshipit-source-id: 3102cacf0
Summary:
Take another page from the Incorrectness Logic book and refrain from reporting issues on paths unless we know for sure that this path will be taken.
Previously, we would report on paths that are merely *not impossible*. This goes very far in the other direction, so it's possible we'll want to go back to some sort of middle ground. Or maybe not. See the changes in the tests to get a sense of what we're missing.
Reviewed By: ezgicicek
Differential Revision: D24014719
fbshipit-source-id: d451faf02
Summary:
Nullifying these leads to observable side-effects, like in the added
test.
Reviewed By: da319
Differential Revision: D23759756
fbshipit-source-id: 559a6486b
Summary:
- freshen up /docs/next/absint-framework to give sensible advice, and
delete outdated bits that are now in the API docs so they remain fresh
- delete SimpleChecker.ml as it's just a source of bitrot
- delete the "adding checkers" page as it's completely outdated and
subsumed by the "AI framework" page + the labs.
Reviewed By: jberdine
Differential Revision: D23597271
fbshipit-source-id: 78b541746
Summary: Most of the time, when the procdesc of a callee is requested, all that is really required is the procedure attributes. However, requesting the procdesc may return `None` when the procedure is undefined (in Java, and soon for Clang too). So, change all callsites to using attributes instead, where possible.
Reviewed By: jvillard
Differential Revision: D23539422
fbshipit-source-id: 3b1a52d48
Summary: There is no reason to write back to the database here, as the resulting procdesc is anyway stored in the summary. This is a source of non-determinism.
Reviewed By: skcho
Differential Revision: D23500220
fbshipit-source-id: 7434e6239
Summary: We only added suffix-stripped prefixes of props but this causes FPS if a component declares props that actually contain suffixes since we strip them when we are adding builder calls. The fix is to add both normal and stripped versions.
Reviewed By: skcho, Katalune
Differential Revision: D23375405
fbshipit-source-id: e99cb4dd8
Summary:
As title.
This diff is co-authored by SungKeun Cho and me.
facebook
This diff is co-authored by skcho and me.
Original comments from skcho
"For the record:
1. Rory and I tried to write models for ObjC iterator.
2. We could not use Java's iterator semantics: In Java's, `hasNext` returns the size of collection, rather than a boolean, and which is used as a control variable. On the other hand, in ObjC, it calls only `nextObject`, not calling `hasNext`, and the return value of which is being checked as `null`.
3. We added an artificial field `objc_iterator_offset` to keep the index of the iterator, and the models added in this diff are handling that integer value.
A problem is that `array.objc_iterator_offset` is not included in the control variables, since the condition of the loop is `nextObject() != null` that does not include the iterator offset. We need to make `array.objc_iterator_offset` as a control variable, by changing the part collecting control variables.
"
Reviewed By: ezgicicek, skcho
Differential Revision: D22944278
fbshipit-source-id: 7e71b79c1
Summary:
This is needed to make dune auto-updating of unit tests introduced in
the next diff cohabit peacefully with our tests to make sure code stays
correctly formatted wrt ocamlformat.
Also, more auto-formatting = better.
Reviewed By: da319
Differential Revision: D22865004
fbshipit-source-id: 91c47ab08
Summary: This diff separates purity analysis and its reporting, since sometimes we want to use the purity analysis results in other checkers, but don't want to report purity issues.
Reviewed By: ezgicicek, jvillard
Differential Revision: D23054913
fbshipit-source-id: 12cc1fc42
Summary: To avoid dead store false positives we skip initialization of a variable that has an `unused` attribute. However, this causes uninitialized value false positives when the variable is later used in macros. To fix this, instead of skipping initialization we record the information about `unused` attribute in local variable data that we can later use for filtering out dead store issues.
Reviewed By: jvillard
Differential Revision: D22868050
fbshipit-source-id: 4a2d0e680
Summary: This diff refactors Java specific `PatternMatch` functions into its own module. When `PatternMatch.ml` was originally created, it was mainly for Java but now it also supports ObjC. Let's refactor it to reflect the Java/ObjC separation: move all functions that operate on Java procnames into Java submodule.
Reviewed By: jvillard
Differential Revision: D22816504
fbshipit-source-id: ff6b64b29
Summary:
We update the type of captured variables to include information about capture mode (`ByReference` or `ByValue`) both for procdesc attributes and the closure expression.
For lambda: closure expression now contains correct capture mode for capture variables. Procdesc still does not contain information about captured variables which we will address in the next diff.
For objc blocks: at the moment all captured variables have mode `ByReference`. Added TODOs to fix this.
Reviewed By: jvillard
Differential Revision: D22572054
fbshipit-source-id: 4c88678ee
Summary: This diff extends the value domain to express multiple markers.
Reviewed By: ngorogiannis
Differential Revision: D22524864
fbshipit-source-id: b8e4af2eb
Summary:
This one is observed to be more memory efficient. Intuitively, maps need
to be re-allocated more often than lists for balancing. In pulse, we'll
often only ever add new values, in increasing order (when they are fresh
variables created as we symbolically execute the program), which pushes
maps into their worst-case allocation pattern. At least I suspect that's
what happens. With lists, this case is handled much better as lists are
not re-allocated when adding elements.
This is somewhat confirmed by benchmarking and observing GC stats.
Reviewed By: skcho
Differential Revision: D22140908
fbshipit-source-id: 29815112f
Summary: This diff adds support for `com.facebook.litho.sections.Section` which mimics the behavior for `com.facebook.litho.Component`.
Reviewed By: skcho
Differential Revision: D22309039
fbshipit-source-id: 3510441a8
Summary:
This diff revises assignment semantics, so it can store/load from the
heap location.
Reviewed By: ezgicicek
Differential Revision: D22042823
fbshipit-source-id: 20d91bfc5
Summary:
Better API for creating issue types:
- distinguish hidden/normal/dynamic issue types
- normal issue types should always be documented
- add "TODO" to missing documentation
- dynamic issue types are the only ones that can be created outside of
IssueType.ml
I had to document the new CCBM and the resource leak lab exercise to
keep Help.ml happy, did `make doc-publish`.
Reviewed By: ngorogiannis
Differential Revision: D22118766
fbshipit-source-id: 3d0194518
Summary:
This diff adds a prototype of a new checker that collects config checkings between markers.
Basically, what the checker is doing is a taint analysis.
* Taint source: function calls of "marker start"
* Taint sink: function calls of config checking
* Taint remove: function calls of "marker end"
By the taint analysis, the analysis results will say that which taints can reach to the sink. In other words, which marker ID that has been started can reach to the config checks, before marker's ending.
I am separating the diff into three steps:
(1/3) Add basic abstract semantics
(2/3) Add trace information
(3/3) Add reporting with test examples
Reviewed By: jvillard
Differential Revision: D21998170
fbshipit-source-id: e7759f62f
Summary:
This diff adds a prototype of a new checker that collects config checkings between markers.
Basically, what the checker is doing is a taint analysis.
* Taint source: function calls of "marker start"
* Taint sink: function calls of config checking
* Taint remove: function calls of "marker end"
By the taint analysis, the analysis results will say that which taints can reach to the sink. In other words, which marker ID that has been started can reach to the config checks, before marker's ending.
I am separating the diff into three steps:
(1/3) Add basic abstract semantics
(2/3) Add trace information
(3/3) Add reporting with test examples
Reviewed By: jvillard
Differential Revision: D21998150
fbshipit-source-id: 337a8938a
Summary:
This diff adds a prototype of a new checker that collects config checkings between markers.
Basically, what the checker is doing is a taint analysis.
* Taint source: function calls of "marker start"
* Taint sink: function calls of config checking
* Taint remove: function calls of "marker end"
By the taint analysis, the analysis results will say that which taints can reach to the sink. In other words, which marker ID that has been started can reach to the config checks, before marker's ending.
I am separating the diff into three steps:
(1/3) Add basic abstract semantics
(2/3) Add trace information
(3/3) Add reporting with test examples
Reviewed By: jvillard
Differential Revision: D21935546
fbshipit-source-id: 092abb92c
Summary:
The past issue with ppx_compare on nonrec types has (at some point)
been fixed. Cf. https://github.com/janestreet/ppx_compare/issues/2
Reviewed By: ngorogiannis
Differential Revision: D21961645
fbshipit-source-id: de03a60a4
Summary:
See previous diff: issues are always reported with the same severity so
recognise that and just use their default severity in "modern" checkers.
Reviewed By: ngorogiannis
Differential Revision: D21904591
fbshipit-source-id: fb5387e35
Summary:
- "visibility" (whether an issue to report is something to show the user
or something that is only used for debugging or for detecting other
issues) is an intrinsic property of an issue type and thus belongs in
`IssueType.t`.
- "severity" (warning/error/...) is something that each issue should
have a default for ("a memory leak is by default an ERROR", a
"condition always true is by default a warning"), but can also be
overriden at run-time. Right now only nullsafe uses that capability:
when in "strict mode", some warnings become errors. We can imagine
extending this to other issue types, or even providing config flags to
turn warnings into errors, like compilers often have.
To guess the default severity (since it's dynamic it can be hard to know
for sure!), I tried to find places where it was reported as the source
of truth, but also later diffs test these defaults against our tests (by
removing most of the dynamic changes in severity).
With this diff there are 3 places where severity is set:
1. The default severity in IssueType.t: this is unused for now.
2. The severity from `Exceptions.recognize_exception`: this is
semi-statically determined and, if set, takes precedence over number 3 (which looks wrong to me!)
3. The severity passed to `Errlog.log_issue` when we actually add an
issue to the error log: this is used only when (2) is unset.
The next diffs will make 1 the default, delete 2, and make 3 optional
but override 1 when passed.
Reviewed By: skcho
Differential Revision: D21904538
fbshipit-source-id: a674b42d8
Summary:
Introduce BIABD_ prefixes for a few issue types that were duplicated
between analyses, and also prefix the lab exercise issue type to avoid
sharing with biabduction.
Reviewed By: ngorogiannis
Differential Revision: D21660226
fbshipit-source-id: 3435916e6
Summary:
Consider the below program,
```
const int gvar = 0;
enum {
cvar = gvar + 1,
};
bool dangling_cvar(int x) {
for (int i = 0; i < cvar; i++){
}
}
```
In the prune node, we don't have `cvar` but its inlined version, i.e. we have ` i < n$2 + 1` and the variable `n$2` is defined not in predecessor nodes to the prune node (as normally one would expect) but in a separate dangling node (see the {F236910156})
:
```
6: BinaryOperatorStmt:Add n$2=*&#GB<test.cpp|ice>$gvar:int [line 38, column 10]
```
When computing the control var of this loop, previously we gave up and simply raised an error.
With this diff, let's handle this case by looking inside this dangling node.
Reviewed By: skcho
Differential Revision: D21525569
fbshipit-source-id: bd4371493
Summary:
Add an extra argument everywhere we report about the identity of the
checker doing the reporting. This isn't type safe in any way, i.e. a
checker can masquerade as another. But, hopefully it's enough to ensure
checker writers (and diff reviewers) have a chance to reflect on what
issue type they are reporting.
Reviewed By: ngorogiannis
Differential Revision: D21638823
fbshipit-source-id: b4a4b0c0a
Summary:
The eventual goal is to document issue types and checkers better, in
particular which issue types "belong" to which checkers. (note:
Currently some issue types are reported by several checkers.)
The plan is to associate a list of "allowed" checkers to each issue type
and (not in this diff) raise a runtime exception if a checker not in
that list tries to report that issue. Hopefully tests cover all the use
cases and there are no surprises. I've filled in the lists by
`git grep`ing which checkers used which issue types in their code.
Reviewed By: ngorogiannis
Differential Revision: D21617622
fbshipit-source-id: 159ab171f
Summary: In an intra-procedural analysis, we assume that parameters passed by reference to a function will be initialized inside that function. To do that we use the type information of a formal parameter to initialize the fields of the struct. This was causing false positives if the formal parameter in function signature had type `void*`. To solve this, we used type information from local variables instead. However, we also get false positives for any kind of pointer if we use cast. We fix this by using type information of local variables as in `void*` case.
Reviewed By: jvillard
Differential Revision: D21522979
fbshipit-source-id: 4222ff134
Summary:
The documentation had gone out of sync with the new library names. Add
or copy some short documentation for the main libraries, i.e. all of
them except individual analyses (and scripts, third party, ..).
The idea is that each library has some toplevel documentation
`infer/src/<library_dir>/<LibraryName>.mld` that is linked to from the
main entry point of the document infer/infer.mld. We can link to some
important modules for each library from within their toplevel
documentation, then the actual documentation should live inside the
.mli's of the modules of the library as appropriate.
Hopefully this leads to better documentation over time. At least now we
can write some docs and they'll end up somewhere nice. Lots can be
improved still at this point.
Reviewed By: ngorogiannis
Differential Revision: D21551955
fbshipit-source-id: 69a0cfa44
Summary:
This diff adds semantics of assume null, heuristics. When `assume(x == null)`, it removes the
methods called on the builder `*x` from the abstract state.
```
x -> {p}
p -> {method1 called}
assume(x == null)
x -> {p}
```
This heuristics is unsound: Even though `x` (a pointer to builder object) points-to an builder
object, which cannot imply that the object `p` does not exist in the concrete semantics. The
unsoundness may appear when there is an alias (see the FP test added).
Reviewed By: ezgicicek
Differential Revision: D21502923
fbshipit-source-id: 2e392bd89
Summary:
The only thing keeping this module alive were unit tests, proving once
and for all that unit tests are bad.
Reviewed By: ngorogiannis
Differential Revision: D21451855
fbshipit-source-id: e63995732
Summary:
- make quandary an `interprocedural`
- move quandary traces to absint/ since they are also used at least by
SIOF
- no more `Summary.OnDisk.dummy` :')
Reviewed By: ngorogiannis
Differential Revision: D21408391
fbshipit-source-id: cc53d2c6c
Summary:
Needed to move a bunch of files around to make this happen. Notably,
moving "preanal.ml" outside of checkers/ into backend/ since it needs to
modify the proc desc in the summary. Also hoisting goes to cost/.
Reviewed By: skcho
Differential Revision: D21407069
fbshipit-source-id: ebb9b78ec
Summary:
Changing inferbo required changing all the analyses that depend on it
too. This introduces a new feature of the the new framework: the ability
for the checkers to read other analyses' payloads in a more functional
way.
Reviewed By: ezgicicek, skcho
Differential Revision: D21401819
fbshipit-source-id: f9b99e344
Summary:
An easy one. Will be needed eventually to make checkers/ its own dune
library.
Reviewed By: ngorogiannis
Differential Revision: D21401818
fbshipit-source-id: 64e8a4bf4
Summary:
This module needs to be above all checkers since it knows about all the
checkers; put it at the same level of ondemand and callbacks.
Reviewed By: ezgicicek
Differential Revision: D21401821
fbshipit-source-id: f40dba6dd
Summary:
- move a few files from checkers/ so that nullsafe can depend on them
- nullsafe depends on a few files in biabduction/ via Errdesc (not the
biabduction analysis itself but some datatypes and functionality):
- when possible, I've moved the individual functions elsewhere, in absint/Decompile.ml
- nullsafe still depends on a function in Errdesc that unfortunately
depends on a bunch of biabduction datatypes like Prop(!) and some
other functionality that for now is embedded in biabduction
(substitution in SIL instructions).
Reviewed By: mityal
Differential Revision: D21351906
fbshipit-source-id: 757528120
Summary:
Easy cleanup. The tenv is now part of the analysis_data that is in the
closure passed to the Dataflow framework.
Reviewed By: dulmarod
Differential Revision: D21351907
fbshipit-source-id: 592542c06
Summary:
This is to eventually remove eradicate's dependency on Ondemand and
other modules in backend/.
Reviewed By: mityal
Differential Revision: D21351456
fbshipit-source-id: 1c4723cbc
Summary:
Add a new data structure and use it for the map of memory accesses to
limit the number of destinations reachable from a given address. This
avoids remembering details of each index in large arrays, or even each
field in large structs.
Reviewed By: skcho
Differential Revision: D18246091
fbshipit-source-id: 5d3974d9c
Summary:
This shows how the strategy for making each analysis its own library
looks like. Starting with biabduction since it's one of the worst ones.
A checker cannot depend on ProcData (in its current form) as it contains
a Summary.t. We don't want to change all the analyzers at once so let's
make up a new type. The new type also contains callbacks for Ondemand
since a checker that is its own dune library cannot call Ondemand
directly either (because Ondemand needs Summary.OnDisk).
Once all checkers are migrated we should be able to reclaim the
callbacks set up by callbacks.ml in exchange for these new callbacks,
therefore achieving a neutral callback karma.
Reviewed By: dulmarod, skcho
Differential Revision: D21261638
fbshipit-source-id: fa91ca50f
Summary:
Looks like this one was already causing circular dependency issues!
Saves threading the callback through *many* functions.
Reviewed By: ngorogiannis
Differential Revision: D21261636
fbshipit-source-id: 2b23aa07d
Summary:
absint/ is its own dune library. There was one last obstacle: we need
callbacks to `NodePrinter`. We'll add more to `AnalysisCallbacks` in future
diffs.
Reviewed By: ngorogiannis
Differential Revision: D21257476
fbshipit-source-id: 3a2ddef14
Summary:
`ProcData.t` contains a `Summary.t`. Eventually we want to fix this too
so that checkers don't depend on backend/, i.e. on all the other
checkers via Summary.ml. But in order to migrate progressively we can
first migrate absint/ and one step on the way is for it to not know what
kind of analysis data it is passing around.
This extra flexibility only costs us passing an extra `Procdesc.t` in a
couple more functions so it's actually not a bad change in itself.
Reviewed By: ngorogiannis
Differential Revision: D21257466
fbshipit-source-id: a91f7b191
Summary:
This is needed to make absint/ its own dune library. Modules in absint/
cannot depend on modules in backend/. This is because backend/Summary.ml
depends on *all* the (inteprocedural) analyses since its stores elements
of their domains. But analyses are supposed to depend on absint/ to
use the AI framework and others. Thus absint/ cannot depend on backend/
otherwise it creates a dependency cycle.
Right now infer builds with this cycle because we consider all these
directories to be one library and there is no dependency cycle between
the individual modules, but making absint/ a library makes the situation
coarser.
One actual change in there: one function in PatternMatch was specific to
nullsafe and was moved there.
Reviewed By: ngorogiannis
Differential Revision: D21257467
fbshipit-source-id: 42af43315
Summary:
This is a step in disentangling the various analyses: that file used to
make every checker on biabduction because of a few of its functions that
use biabduction datatypes.
Split reporting.ml into:
- Reporting.ml: the functions all checkers need to report errors. This
is put in absint/ with the other files that are needed by all
checkers.
- SummaryReporting.ml: functions that need to depend on Summary.ml
(useful for later). This is put in backend/ where Summary.ml lives.
- BiabductionReporting.ml: for the biabduction analysis
The rest of the changes are renames to use the appropriate module
amongst the above.
Reviewed By: ngorogiannis
Differential Revision: D21257468
fbshipit-source-id: fa28cefbc
Summary:
This fixes a long-standing TODO. I re-ordered the lines by:
- first putting each entry on a single line (replacing "^J " -> " "
in emacs)
- then using emacs' M-x reverse-region
- then auto-formatting again
Reviewed By: skcho
Differential Revision: D21257475
fbshipit-source-id: 91b780a5d
Summary: D21155014 replaced `skip` call with a Load but this was not right. Instead, let's add a new builtin function (rather than skip) so that other analyses can freely model it as they want.
Reviewed By: jvillard
Differential Revision: D21178286
fbshipit-source-id: c214ccfb0
Summary:
Now that the shape of the record type of AbductiveDomain.t is known, we
don't need this getter anymore. Keep `get_pre` and `get_post` as they
perform useful casting to `BaseDomain.t`.
Reviewed By: ezgicicek
Differential Revision: D21022924
fbshipit-source-id: 340f4edf8
Summary:
The "interface" modules define short forms for the internals of pulse
and also serve as a guide of which modules you are supposed to use at
which "level" in the pulse domains (base domain vs abductive domain vs
higher-level PulseOperations.ml). Make sure they are used.
Reviewed By: skcho
Differential Revision: D21022927
fbshipit-source-id: f890df245
Summary:
The full inventory of everything in infer-out/. The main change is
around "issues directories": instead of registering them dynamically
they are now all declared statically (well, they kind of were already in
Config.ml).
Reviewed By: ngorogiannis
Differential Revision: D20894305
fbshipit-source-id: 1a06ec09d
Summary:
As soon as pulse detects an error, it completely stops the analysis and loses the state where the error occurred. This makes it difficult to debug and understand the state the program failed. Moreover, other analyses that might build on pulse (e.g. impurity), cannot access the error state.
This diff aims to restore and display the state at the time of the error in `PulseExecutionState` along with the diagnostic by extending it as follows:
```
type exec_state =
| represents the state at the program point that caused an error *)
```
As a result, since we don't immediately stop the analysis as soon as we find an error, we detect both errors in conditional branches simultaneously (see test result changes for examples).
NOTE: We need to extend `PulseOperations.access_result` to keep track of the failed state as follows:
```
type 'a access_result = ('a, Diagnostic.t * t [denoting the exit state] ) result
```
Reviewed By: jvillard
Differential Revision: D20918920
fbshipit-source-id: 432ac68d6
Summary: Consider functions that simply exit as impure by extending the impurity domain with `AbstractDomain.BooleanOr` that signifies whether the program exited.
Reviewed By: skcho
Differential Revision: D20941628
fbshipit-source-id: 19bc90e66
Summary:
Java bytecode format does not record the declarations location
for classes and fields. We set up a first infrastructure to recover this
information. Currently we only track location for classes and only gives
the first line of the corresponding source file. We will enhance this location
with source file (baby) parsing in a next diff.
Reviewed By: mityal
Differential Revision: D20868187
fbshipit-source-id: d355475e9
Summary:
This diff lifts the `PulseAbductiveDomain.t` in `PulseExecutionState` by tracking whether the program continues the analysis normally or exits unusually (e.g. by calling `exit` or `throw`):
```
type exec_state =
| ContinueProgram of PulseAbductiveDomain.t (** represents the state at the program point *)
| ExitProgram of PulseAbductiveDomain.t
(** represents the state originating at exit/divergence. *)
```
Now, Pulse's actual domain is tracked by `PulseExecutionState` and as soon as we try to analyze an instruction at `ExitProgram`, we simply return its state.
The aim is to recover the state at the time of the exit, rather than simply ignoring them (i.e. returning empty disjuncts). This allows us to get rid of some FNs that we were not able to detect before. Moreover, it also allows the impurity analysis to be more precise since we will know how the state changed up to exit.
TODO:
- Impurity analysis needs to be improved to consider functions that simply exit as impure.
- The next goal is to handle error state similarly so that when pulse finds an error, we recover the state at the error location (and potentially continue to analyze?).
Disclaimer: currently, we handle throw statements like exit (as was the case before). However, this is not correct. Ideally, control flow from throw nodes follows catch nodes rather than exiting the program entirely.
Reviewed By: jvillard
Differential Revision: D20791747
fbshipit-source-id: df9e5445a
Summary:
Fix all the docstrings that `odoc` or `ocamlformat` is not happy about.
Delete all `[@@ocamlformat "parse-docstring = false"]` pragmas as a
result.
Reviewed By: jberdine, ngorogiannis
Differential Revision: D20798913
fbshipit-source-id: 728d9e45c
Summary:
This declaration is heavily used in Guava library.
Quick inspection shows that majority of methods are annotated correctly.
This will hide previosly hidden unsoundness issues in the codebase.
Reviewed By: artempyanykh
Differential Revision: D20737104
fbshipit-source-id: aa048bfc1
Summary: In an intra-procedural analysis we assume that parameters passed by reference to a function will be initialized inside that function. We use the type information of an actual parameter to initialize the fields of the struct. This does not work if a function has a parameter of type void* as the actual parameters also has type void*. To solve this issue, we use type information from local variables.
Reviewed By: jvillard
Differential Revision: D20670253
fbshipit-source-id: dc9f051ef
Summary:
- Model `System.exit()` as early_exit and add a test
- Tweak message of methods that are impure due to having no pulse summary (and add a test)
Reviewed By: skcho
Differential Revision: D20668979
fbshipit-source-id: 6b5589aae
Summary:
As exemplified by added tests, pulse computes an empty summary (with 0 disjuncts) whenever it discovers a contradiction which might be caused by:
- discovering aliasing in memory
- widening limited number of times in loops and concluding that loop exit conditions are never taken
However, AFAIU, it is not possible to have a function with 0 disjunct apart from such anomalities. Even a function which does nothing like `void foo(){}` has 1 disjuncts:
```
Pulse: 1 pre/post(s)
#0: PRE:
{ roots={ };
mem ={ };
attrs={ };}
POST:
{ roots={ };
mem ={ };
attrs={ };}
SKIPPED_CALLS: { }
```
The aim of this diff is to consider functions with 0 disjuncts as **impure** because most often such cases are impure, rather than actually pure.
Reviewed By: skcho
Differential Revision: D20619504
fbshipit-source-id: 3a8502c90
Summary:
- Add more naive pulse models for:
- `System.arraycopy`
- `StringBuilder.setLength`
- `StringBuilder.delete`
- Model the following as pure
- `SparseArrayCompat.valueAt`
- `File.get...`
- Add a nice test
Reviewed By: jvillard
Differential Revision: D20513397
fbshipit-source-id: 6d412d13a
Jules Villard
Nikos Gorogiannis
Ezgi Çiçek
Dulma Churchill
Qianyi Shu
Sungkeun Cho
Daiva Naudziuniene
Josh Berdine
David Pichardie
Mitya Lyubarskiy