Summary:
If -fembed-bitcode is passed, it leads to multiple cc1 commands, which
try to read .bc files that don't get generated, and fail. So pass
-fembed-bitcode=off to disable.
Reviewed By: martinoluca
Differential Revision: D5516879
fbshipit-source-id: 478057a
Summary:
If you run `infer report --issues-txt ilovecats.txt ...` then bugs may mysteriously miss from `ilovecats.txt`, unless you flush. (See rules of thumb for `Format` module.)
Closes https://github.com/facebook/infer/pull/694
Reviewed By: mbouaziz
Differential Revision: D5442335
Pulled By: jvillard
fbshipit-source-id: 73272a0
Summary:
The python scripts support this option but don't do anything with it. Note:
This doesn't remove support for android harnesses.
Reviewed By: sblackshear
Differential Revision: D5501019
fbshipit-source-id: 14c4e3f
Summary: The `--failures-allowed` was doing for the Clang frontend what `--keep-doing` was doing for the backend. This revision merges the two options to simplify the Infer CLI and our tests.
Reviewed By: jvillard
Differential Revision: D5474347
fbshipit-source-id: 09bcea4
Summary:
update-submodule: facebook-clang-plugins
Moving to a newer version of clang, see ffb5dd0114
Reviewed By: jvillard
Differential Revision: D5452529
fbshipit-source-id: 28bc215
Summary:
Better to bail early than have mysterious failures. These used to have the wrong error messages:
```
$ cd examples/android_hello/
$ infer -- ./gradlew rubbish
Capturing in gradle mode...
Running and capturing gradle compilation...
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] FAILURE: Build failed with an exception.
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] * What went wrong:
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Task 'rubbish' not found in root project 'android_hello'.
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter]
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] * Try:
10:46:56.730 [ERROR] [org.gradle.internal.buildevents.BuildExceptionReporter] Run gradlew tasks to get a list of available tasks. Run with --stacktrace option to get the stack trace.
Nothing to compile. Try running `./gradlew clean` first.
ERROR: (Unix.Exit_or_signal (Exit_non_zero 66))
$ cd -
$ infer --flavors --Xbuck --keep-going -- buck build //toto:toto
Capturing in buck mode...
moving files in buck-out to buck-out/.trash/buck-outwiiL6N
Not using buckd because watchman isn't installed.
BUILD FAILED: No build file at toto/BUCK when resolving target //toto:toto#infer.
Buck failed, but continuing the analysis because --keep-going was passed
Not using buckd because watchman isn't installed.
No build file at toto/BUCK when resolving target //toto:toto#infer.
Traceback (most recent call last):
File "/home/jul/infer/infer/bin/../lib/python/infer.py", line 186, in <module>
main()
File "/home/jul/infer/infer/bin/../lib/python/infer.py", line 168, in main
capture_exitcode = imported_module.gen_instance(args, cmd).capture()
File "/home/jul/infer/infer/lib/python/inferlib/capture/buck.py", line 89, in capture
return self.capture_with_flavors()
File "/home/jul/infer/infer/lib/python/inferlib/capture/buck.py", line 242, in capture_with_flavors
result_paths = self._get_analysis_result_paths()
File "/home/jul/infer/infer/lib/python/inferlib/capture/buck.py", line 148, in _get_analysis_result_paths
out = [x.split(None, 1)[1] for x in buck_output.strip().split('\n')]
IndexError: list index out of range
ERROR: (Unix.Exit_or_signal (Exit_non_zero 1))
$ cd infer/build_systems/ant/ && infer -- ant rubbish
Capturing in ant mode...
BUILD FAILED
Target "rubbish" does not exist in the project "null".
at org.apache.tools.ant.Project.tsort(Project.java:1929)
at org.apache.tools.ant.Project.topoSort(Project.java:1837)
at org.apache.tools.ant.Project.topoSort(Project.java:1800)
at org.apache.tools.ant.Project.executeTarget(Project.java:1376)
at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
at org.apache.tools.ant.Project.executeTargets(Project.java:1260)
at org.apache.tools.ant.Main.runBuild(Main.java:857)
at org.apache.tools.ant.Main.startAnt(Main.java:236)
at org.apache.tools.ant.launch.Launcher.run(Launcher.java:287)
at org.apache.tools.ant.launch.Launcher.main(Launcher.java:113)
Total time: 0 seconds
Nothing to compile. Try running `ant clean` first.
ERROR: (Unix.Exit_or_signal (Exit_non_zero 66))
```
Now we fail better, for instance:
```
$ infer --flavors --Xbuck --keep-going -- buck build //toto:toto
Capturing in buck mode...
moving files in buck-out to buck-out/.trash/buck-outHag8Ji
Not using buckd because watchman isn't installed.
BUILD FAILED: No build file at toto/BUCK when resolving target //toto:toto#infer.
Buck failed, but continuing the analysis because --keep-going was passed
Not using buckd because watchman isn't installed.
No build file at toto/BUCK when resolving target //toto:toto#infer.
ERROR: (Unix.Exit_or_signal (Exit_non_zero 70))
$ cd infer/build_systems/ant/ && infer -- ant rubbish
Capturing in ant mode...
BUILD FAILED
Target "rubbish" does not exist in the project "null".
at org.apache.tools.ant.Project.tsort(Project.java:1929)
at org.apache.tools.ant.Project.topoSort(Project.java:1837)
at org.apache.tools.ant.Project.topoSort(Project.java:1800)
at org.apache.tools.ant.Project.executeTarget(Project.java:1376)
at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
at org.apache.tools.ant.Project.executeTargets(Project.java:1260)
at org.apache.tools.ant.Main.runBuild(Main.java:857)
at org.apache.tools.ant.Main.startAnt(Main.java:236)
at org.apache.tools.ant.launch.Launcher.run(Launcher.java:287)
at org.apache.tools.ant.launch.Launcher.main(Launcher.java:113)
Total time: 0 seconds
ERROR: couldn't run compilation command `['ant', '-verbose', u'rubbish']`
ERROR: (Unix.Exit_or_signal (Exit_non_zero 1))
```
Reviewed By: jeremydubreil
Differential Revision: D5469607
fbshipit-source-id: a3eb05c
Summary:
The way we represented container writes before was pretty hacky: just use a dummy field for the name of the method that performs the container write.
This diff introduces a new access kind for container writes that is much more structured.
This will make it easier to soundly handle aliasing between containers and support container reads in the near future.
Reviewed By: da319
Differential Revision: D5465747
fbshipit-source-id: e021ec2
Summary: Using a dedicated abstract domain, like Quandary does, is more suitable for taint analysis.
Reviewed By: sblackshear
Differential Revision: D5473794
fbshipit-source-id: c917417
Summary: Because making a diff which breaks the tests because it silently fails to create the right posts for the models is notoriously hard to debug
Reviewed By: sblackshear
Differential Revision: D5471611
fbshipit-source-id: ef04539
Summary:
Both `stringWithUTF8String` and `stringWithString` implements copy semantics that copies the content of their parameter into a newly allocated buffer. We modeled this as pointer assignment in the past, which means that once we write
```
NSString* foo() {
char buf[...];
...
return [NSString stringWithUTF8String:buf];
}
```
We are going to get a spurious stack variable address escape report because local pointer `buf` is assigned to the newly created string and the string gets returned.
This diff tries to address the issue by heap-allocating a buffer and `memcpy` the contents in `stringWithUTF8String` and `stringWithString`. But this change will create another problem: the allocated buffer will be reported as leaked by the backend, while in reality those buffers won't actually be leaked as they are allocated in a region that will be periodically autoreleased. To suppress spurious memory leak FPs, I added another attribute `Awont_leak` that will suppress the leakage report on any expressions that get tagged with it.
Reviewed By: jeremydubreil
Differential Revision: D5403084
fbshipit-source-id: df6de7f
Summary: This gives us more expressive power when defining sources--we can use heuristics like "`foo(o)` only returns a source when `o` is not a constant".
Reviewed By: jvillard
Differential Revision: D5467935
fbshipit-source-id: f3d581d
Summary: This should make it faster to use embarassingly big regexps in AL.
Reviewed By: mbouaziz
Differential Revision: D5462938
fbshipit-source-id: 0431730
Summary:
Pretty basic: warn when we see an assignment instruction `x = ...` and `x` is not live in the post of the instruction.
Only enabled for Clang at the moment because linters already warn on this for Java. But we can enable it later if we want to (should be fully generic).
Reviewed By: jeremydubreil
Differential Revision: D5450439
fbshipit-source-id: 693514c
Summary:
oops_house
This was introduced when upgrading Core, as `Unix.readdir` became deprecated in
favour of `Unix.readdir_opt` but the exception-based logic was left unchanged.
Reviewed By: mbouaziz
Differential Revision: D5461353
fbshipit-source-id: c0994c3
Summary:
Phony dependencies are not good for incrementality. Retain the nice
factorization of code introduced by D5415318 but depend directly on the
relevant files instead of the phony target.
Reviewed By: mbouaziz
Differential Revision: D5461188
fbshipit-source-id: 069519b
Summary: Making it simple to add a new access type for "un-annotated interface call" in an upcoming diff.
Reviewed By: da319
Differential Revision: D5445914
fbshipit-source-id: f29e342
Summary: We get the wrong answer on most of them for now, but that is expected
Reviewed By: ngorogiannis
Differential Revision: D5429242
fbshipit-source-id: 4899079
Summary:
The previous version
- assumed that `infer` was in `PATH`
- would pick any old `infer` in `PATH` and not necessarily the right version
Reviewed By: mbouaziz
Differential Revision: D5433624
fbshipit-source-id: a59be3d
Summary: Long lists will be broken into lines rather than stretch out on a single line.
Reviewed By: jvillard
Differential Revision: D5424323
fbshipit-source-id: 115f16a
Summary:
This commit avoids precision loss on pruning.
// x -> [s$1, s$2]
if(x) { ... }
// x -> ?
before: x -> [min(0, s$1), max(0, s$2)]
because two x values, [0, 0] (true case) and [s$1, s$2] (false case), were joined after the if branch.
after: x -> [s$1, s$2]
Reviewed By: mbouaziz
Differential Revision: D5431009
fbshipit-source-id: 14a9efe
Summary:
Infer is only using clang's AST which means it can ignore flags passed to LLVM backend via `-mllvm` flag.
It will make it easier to maintain compatibility between different versions of clang/LLVM (ie. when flag is not available in LLVM used by infer)
Reviewed By: jvillard
Differential Revision: D5423685
fbshipit-source-id: a9de681
Summary: Changing .inferconfig can change the analysis results, so we want the cache to get invalidated when .inferconfig changes.
Reviewed By: jeremydubreil
Differential Revision: D5419734
fbshipit-source-id: 01ad874
Summary:
This just makes the warnings silent for now. We may improve the analysis to check if the null check on the captured fields are consistent with the annotation on the corresponding parameters.
Eradicate also has the same issue. I added a test to outline this. The biabduction analysis will also probably fail on the same of annotation lookup. We may want implement the proper fix at the level of `Annotation.field_has_annot`.
Reviewed By: sblackshear
Differential Revision: D5419243
fbshipit-source-id: 6460de8
Summary: This way, if infer crashes then the log files will be available for inspection, but if it succeeds we still get rid of the (non-deterministic) logs before Buck caches the results.
Reviewed By: sblackshear
Differential Revision: D5416032
fbshipit-source-id: 22e58be
Summary:
Fixes 2 issues with the build:
- The OCaml dependencies (Version.ml, atdgen-generated stuff, ...) would be generated twice when running `make -j test` from a clean tree, because `make` has no inter-Makefile visibility over common dependencies.
- We would run `atdgen` twice: once for the .ml, once for the .mli, even though one invocation is enough for both.
Add `make ocaml_clean` to nuke only the OCaml code (in particular because
rebuilding the C++ code in the plugin is slow when all I want to get rid of the
OCaml stuff).
Reviewed By: mbouaziz
Differential Revision: D5415318
fbshipit-source-id: 16f42c6
Summary:
First steps towards implementing diff analysis functionalities inside infer
itself. What works: run infer, checkout parent, re-run infer, checkout top
revision, compute the reportdiff (but no final surfacing on the console). Lots
of TODO still, inlined in the code.
Reviewed By: jberdine
Differential Revision: D5364226
fbshipit-source-id: 5b7f9a5
Summary:
Allowing the user to configure where to store the JSON report is asking for
trouble. In fact, some places in the code hardcoded "results.json" anyway.
Someone wanting to have results.json somewhere else can still copy report.json
once infer has run.
Reviewed By: jberdine
Differential Revision: D5415079
fbshipit-source-id: 9439cb6
Summary:
This reverts commit 7177bb6b8af1404fde408ead4750ef48ed9bdaff.
In practice, `extract_filepath` exhausts the call stack, leading to "RuntimeError: maximum recursion depth exceeded" exceptions. Perhaps a loop needs to be used instead.
Reviewed By: jvillard
Differential Revision: D5409892
fbshipit-source-id: 09ccccd
Summary: CFG nodes were not connected and some instructions ended up in wrong place. Fix those issues
Reviewed By: dulmarod
Differential Revision: D5406720
fbshipit-source-id: 2a70e1a
Summary: Introduce `Logging.die` to try and exit with consistent error codes depending on what failed.
Reviewed By: mbouaziz
Differential Revision: D5406642
fbshipit-source-id: 25d98fc
Summary: This will allow us to gradually get rid of the exceptions thrown during the analysis while detecting the regressions earlier
Reviewed By: jberdine, jvillard
Differential Revision: D5385154
fbshipit-source-id: 605e3f5
Summary:
Problem: The analyzer did not know that the value of `v.size()` is an alias of `v.infer_size`, so `v.infer_size` is not pruned by the if condition. As a result it raises a false alarm.
void safe_access(std::vector<int> v) {
if (v.size() >= 10) {
v[9] = 1; // error: BUFFER_OVERRUN Offset: [9, 9] Size: [5, 5]
}
}
void call_safe_access_Good() {
std::vector<int> v(5, 0);
safe_access(v);
}
Solution: Adding alias for return value to the abstract domain.
Now Inferbo can prune `v.infer_size` because it knows that the value of `v.size()` is an alias of `v.infer_size`. There is already an alias domain in Inferbo, so we added a specific room for the retrun value.
Reviewed By: jvillard, mbouaziz
Differential Revision: D5396988
fbshipit-source-id: 4a4702c
Summary:
1. Allow it to forward -version calls to javac (so that if the build system wants
to check the compiler version it doesn't end up with Infer's version)
2. Preserve empty arguments:
javac -bootclasspath "" -classpath a.jar ...
currently gives:
javac: invalid flag: a.jar
Closes https://github.com/facebook/infer/pull/688
Differential Revision: D5406058
Pulled By: jvillard
fbshipit-source-id: 7fa1bcf
Summary:
Conversion and reformat of infer source using ocamlformat
auto-formatting tool.
Current status:
- Because Reason does not handle docstrings, the output of the
conversion is not 'Warning 50'-clean, meaning that there are
docstrings with ambiguous placement. I'll need to manually fix
them just before landing.
Reviewed By: jvillard
Differential Revision: D5225546
fbshipit-source-id: 3bd2786
Summary:
Add support for converting without actually converting. To be used as
a landing pad for rebasing over the conversion.
Reviewed By: jvillard
Differential Revision: D5379967
fbshipit-source-id: 1bd932d
Summary: Adding to the Quandary tests, the list of tests that are already working for the bi-abduction based taint analysis.
Reviewed By: sblackshear
Differential Revision: D5395734
fbshipit-source-id: c4f2e79
Summary:
Error'ing when getting several subcommands on the command line only makes sense
when the user typed these options herself. This was causing a bug in the Gradle
integration, and possibly others (see GitHub issue).
Fixes#668
Reviewed By: jeremydubreil
Differential Revision: D5381850
fbshipit-source-id: f332377
Summary:
Fixes#683
Disclaimer: I don't know what XML namespaces/namespace prefixes are, but this seems to do the trick.
Reviewed By: mbouaziz
Differential Revision: D5381480
fbshipit-source-id: 3da16e7
Summary: This will allow to replace type vars into concrete types in expressions.
Reviewed By: jvillard, mbouaziz
Differential Revision: D5209276
fbshipit-source-id: c1650f8
Summary:
The thread safety domain manipulates access paths that are a variable
followed by a sequence of field or index accesses. Some expressions
from C++ code do not fit that form, such as cases where subtraction of
an offset from a pointer is used to obtain another pointer, whose
fields are then accessed. Previously the analyzer would crash on such
expressions. This diff partially treats them by introducing dummy
variables.
Reviewed By: da319
Differential Revision: D5343567
fbshipit-source-id: f73b520
Summary:
:
because otherwise people would believe they can use the internal representation of these std lib but it fails for our models.
Reviewed By: jvillard
Differential Revision: D5368671
fbshipit-source-id: 4e53d5a
Summary: So that it get rebuilt. Test is clang_compilation_db_relpath
Reviewed By: mbouaziz
Differential Revision: D5364561
fbshipit-source-id: 8cae984
Summary:
:
Get rid of model location in reports.
The goal is to avoid changing `issues.exp` whenever a model is updated.
Reviewed By: jvillard
Differential Revision: D5356608
fbshipit-source-id: 88ecaba
Summary: This could generate enormous amounts of logs on medium-sized projects (eg rocksdb) when running with `--stats`. Review other debug levels in inferbo as well.
Reviewed By: mbouaziz
Differential Revision: D5364139
fbshipit-source-id: 5c8d206
Summary:
In C++ it may happen that a procedure return 'variable' is an access
path that cannot be translated to Hil. For now just skip these instead
of crashing.
Reviewed By: mbouaziz
Differential Revision: D5356134
fbshipit-source-id: 977dfba
Summary:
They are expected to occur in C++ code, so don't fail on them. For now
just skip them, although a better treatment of dynamic dispatch may be
needed later.
Reviewed By: da319, mbouaziz
Differential Revision: D5292462
fbshipit-source-id: 4285514
Summary:
Indexing into a string literal expression would generate a fresh
variable on every application of a transformer. This violated
finiteness of the domain, and caused divergence.
Reviewed By: da319
Differential Revision: D5342951
fbshipit-source-id: e95e84e
Summary: It was passing the argument multiple times rather than once with all the accepted values
Reviewed By: jvillard
Differential Revision: D5338509
fbshipit-source-id: 22b86a5
Summary: This is useful when we only want to examine the html for some but not all source files.
Reviewed By: jvillard
Differential Revision: D5334786
fbshipit-source-id: 774c23c
Summary:
It instantiates fields of structures when a pointer to which is given
as a function parameter, e.g., `foo(&s);`.
Reviewed By: mbouaziz, jvillard
Differential Revision: D5337645
fbshipit-source-id: c06da29
Summary: Rename historical option to its new form, since the old form was no longer accepted by infer.
Reviewed By: martinoluca
Differential Revision: D5329033
fbshipit-source-id: 4fa9402
Summary:
We keep track of both `beginPtr` and `endPtr` but the modelling was mostly
about `beginPtr` as some sort of approximation I guess. This shouldn't change
much but will be useful later when doing more iterator stuff.
Reviewed By: mbouaziz
Differential Revision: D5255772
fbshipit-source-id: 0f6e3e8
Summary:
This will be needed to re-use the functions now in Driver.ml in other contexts
without always adding to infer.ml. For instance, this is used in a later diff
to do a diff-analysis orchestrator that needs to run the capture and analysis
several times.
Reviewed By: jberdine
Differential Revision: D5319862
fbshipit-source-id: caf9551
Summary: Needed in a later diff to be able to compute the set of changed files *during* an infer execution.
Reviewed By: jberdine
Differential Revision: D5319667
fbshipit-source-id: 226ec91
Summary: This seems to move in the right direction. Also, `const operator[]` did not do an `access_at`, which I fixed.
Reviewed By: mbouaziz
Differential Revision: D5320427
fbshipit-source-id: c31c5ea
Summary: Unknown library returns the unknown pointer as well as the top interval.
Reviewed By: mbouaziz, jvillard
Differential Revision: D5282669
fbshipit-source-id: 34c7e18
Summary:
Thanks to the logging introduced in D5293334 (or because of, depending on your liking of spam), I noticed that there lots of errors being logged of the form
Couldn't read multilink file '/home/jul/infer/infer/tests/codetoanalyze/cpp/errors/infer-out/attributes/d0/multilink.txt': /home/jul/infer/infer/tests/codetoanalyze/cpp/errors/infer-out/attributes/d0/multilink.txt: No such file or directory
I don't think it makes sense to care about multilink files except when `--merge` is specified.
Also introduced a .mli and self-documented a function.
Reviewed By: akotulski
Differential Revision: D5310129
fbshipit-source-id: c3a6276
Summary:
Once the fixed/preexisting/introduced sets have been computed, they endure
further filtering which may decide that more of them are equal. These bugs just
get dropped on the floor. Put these into preexisting as well instead, at least
in the case of the "skip_duplicated_types_on_filenames" filter.
Reviewed By: martinoluca
Differential Revision: D5274248
fbshipit-source-id: 99b3f3d
Summary:
This diff tries to achieve the followings: if we have the following C++ codes:
```
bool foo(int x, int y) {
return &x == &y;
}
```
We want the C++ frontend to emit Sil as if the input is written as
```
bool foo(int x, int y) {
if (&x == &y) return 1; else return 0;
}
```
This matches the behavior of our Java frontend.
The reason why we prefer an explicit branch is that it will force the backend to eagerly produce two different specs for `foo`. Without the explicit branch, for the above example the backend would produce one spec with `return = (&x == &y)` as the post condition, which is not ideal because (1) we don't want local variables to escape to the function summary, and (2) with the knowledge that no two local variables may alias each other, the backend could actually determines that `&x == &y` is always false, emitting a more precise postcondition `return = 0`. This is not possible if we do not eagerly resolve the comparison expression.
Reviewed By: akotulski
Differential Revision: D5260745
fbshipit-source-id: 6bbbf99
Summary:
:
There are throw wrapper functions like `std::__throw_bad_alloc()` defined in both libstdc++ (https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/bits/functexcept.h) and libc++ (e.g. 907c1196a7/include/new (L145)). Folly actually exports some of them as well (diffusion/FBS/browse/master/fbcode/folly/portability/BitsFunctexcept.h). The function body of those wrappers merely throws the corresponding exception. My understanding is that the primary purpose of the wrappers is to throw the exception if everything goes well and to fall back to something reasonable when exception is disabled (e.g. when `-fno-exceptions` is passed to the compiler).
The problem is that infer doesn't really understand what those functions do, and I've seen some false positives get reported as a result of it. So to remove those FPs we need to either model them or handle them specially. Modeling those wrappers by either whitelisting them or overriding the include files turns out to be difficult, as those wrappers are only declared but not defined in the STL headers. Their implementations are not available to Infer so whitelisting them does nothing, and if I provide custom implementations in the headers then normal compilation process will be disrupted because the linker would complain about duplicated implementation.
What I did here is to replace functions whose name matches one of the throw wrapper's name with a `BuiltinDecls.exit`. I have to admit that this is a bit hacky: initially I was trying to do something more general: replacing functions with `noreturn` attribute with `BuitinDecls.exit`. That did not work because, CMIIW, the current frontend only exports function attributes for functions with actual bodies, not declaration-only functions. I'd love to be informed if there are better ways to handle those wrappers.
Reviewed By: jeremydubreil
Differential Revision: D5266030
fbshipit-source-id: 4580227
Summary:
:
Do not store dummy `_` into the stack.
This makes debugging a lot easier
Reviewed By: skcho
Differential Revision: D5275941
fbshipit-source-id: ce329a5
Jeremy Dubreil
Sam Blackshear
Josh Berdine
Jules Villard
Jia Chen
Radu Grigore
Andrzej Kotulski
Dino Distefano
Martino Luca
Mehdi Bouaziz
Sungkeun Cho
Kyriakos Nikolaos Gkorogiannis
Dulma Churchill
Pavel Grafov
azhdar
Kihong Heo
Daiva Naudziuniene
Alexander Slesarev