Miri

An experimental interpreter for Rust's mid-level intermediate representation (MIR). It can run binaries and test suites of cargo projects and detect certain classes of undefined behavior, for example:

• Out-of-bounds memory accesses and use-after-free
• Invalid use of uninitialized data
• Violation of intrinsic preconditions (an unreachable_unchecked being reached, calling copy_nonoverlapping with overlapping ranges, ...)
• Not sufficiently aligned memory accesses and references
• Violation of some basic type invariants (a bool that is not 0 or 1, for example, or an invalid enum discriminant)
• Experimental: Violations of the Stacked Borrows rules governing aliasing for reference types
• Experimental: Violations of the Tree Borrows aliasing rules, as an optional alternative to Stacked Borrows
• Experimental: Data races

On top of that, Miri will also tell you about memory leaks: when there is memory still allocated at the end of the execution, and that memory is not reachable from a global static, Miri will raise an error.

Miri supports almost all Rust language features; in particular, unwinding and concurrency are properly supported (including some experimental emulation of weak memory effects, i.e., reads can return outdated values).

You can use Miri to emulate programs on other targets, e.g. to ensure that byte-level data manipulation works correctly both on little-endian and big-endian systems. See cross-interpretation below.

Miri has already discovered some real-world bugs. If you found a bug with Miri, we'd appreciate if you tell us and we'll add it to the list!

By default, Miri ensures a fully deterministic execution and isolates the program from the host system. Some APIs that would usually access the host, such as gathering entropy for random number generators, environment variables, and clocks, are replaced by deterministic "fake" implementations. Set MIRIFLAGS="-Zmiri-disable-isolation" to access the real system APIs instead. (In particular, the "fake" system RNG APIs make Miri not suited for cryptographic use! Do not generate keys using Miri.)

All that said, be aware that Miri will not catch all cases of undefined behavior in your program, and cannot run all programs:

• There are still plenty of open questions around the basic invariants for some types and when these invariants even have to hold. Miri tries to avoid false positives here, so if your program runs fine in Miri right now that is by no means a guarantee that it is UB-free when these questions get answered.

  In particular, Miri does not check that references point to valid data.

• If the program relies on unspecified details of how data is laid out, it will still run fine in Miri -- but might break (including causing UB) on different compiler versions or different platforms.

• Program execution is non-deterministic when it depends, for example, on where exactly in memory allocations end up, or on the exact interleaving of concurrent threads. Miri tests one of many possible executions of your program. You can alleviate this to some extent by running Miri with different values for -Zmiri-seed, but that will still by far not explore all possible executions.

• Miri runs the program as a platform-independent interpreter, so the program has no access to most platform-specific APIs or FFI. A few APIs have been implemented (such as printing to stdout, accessing environment variables, and basic file system access) but most have not: for example, Miri currently does not support networking. System API support varies between targets; if you run on Windows it is a good idea to use --target x86_64-unknown-linux-gnu to get better support.

• Weak memory emulation may produce weak behaviours unobservable by compiled programs running on real hardware when SeqCst fences are used, and it cannot produce all behaviors possibly observable on real hardware.

Moreover, Miri fundamentally cannot tell you whether your code is sound. Soundness is the property of never causing undefined behavior when invoked from arbitrary safe code, even in combination with other sound code. In contrast, Miri can just tell you if a particular way of interacting with your code (e.g., a test suite) causes any undefined behavior. It is up to you to ensure sufficient coverage.

Using Miri

Install Miri on Rust nightly via rustup:

rustup +nightly component add miri

If rustup says the miri component is unavailable, that's because not all nightly releases come with all tools. Check out this website to determine a nightly version that comes with Miri and install that using rustup toolchain install nightly-YYYY-MM-DD. Either way, all of the following commands assume the right toolchain is pinned via rustup override set nightly or rustup override set nightly-YYYY-MM-DD. (Alternatively, use cargo +nightly/cargo +nightly-YYYY-MM-DD for each of the following commands.)

Now you can run your project in Miri:

1. Run cargo clean to eliminate any cached dependencies. Miri needs your dependencies to be compiled the right way, that would not happen if they have previously already been compiled.
2. To run all tests in your project through Miri, use cargo miri test.
3. If you have a binary project, you can run it through Miri using cargo miri run.

The first time you run Miri, it will perform some extra setup and install some dependencies. It will ask you for confirmation before installing anything.

cargo miri run/test supports the exact same flags as cargo run/test. For example, cargo miri test filter only runs the tests containing filter in their name.

You can pass arguments to Miri via MIRIFLAGS. For example, MIRIFLAGS="-Zmiri-disable-stacked-borrows" cargo miri run runs the program without checking the aliasing of references.

When compiling code via cargo miri, the cfg(miri) config flag is set for code that will be interpret under Miri. You can use this to ignore test cases that fail under Miri because they do things Miri does not support:

#[test]
#[cfg_attr(miri, ignore)]
fn does_not_work_on_miri() {
    tokio::run(futures::future::ok::<_, ()>(()));
}

There is no way to list all the infinite things Miri cannot do, but the interpreter will explicitly tell you when it finds something unsupported:

error: unsupported operation: can't call foreign function: bind
    ...
    = help: this is likely not a bug in the program; it indicates that the program \
            performed an operation that the interpreter does not support

Cross-interpretation: running for different targets

Miri can not only run a binary or test suite for your host target, it can also perform cross-interpretation for arbitrary foreign targets: cargo miri run --target x86_64-unknown-linux-gnu will run your program as if it was a Linux program, no matter your host OS. This is particularly useful if you are using Windows, as the Linux target is much better supported than Windows targets.

You can also use this to test platforms with different properties than your host platform. For example cargo miri test --target s390x-unknown-linux-gnu will run your test suite on a big-endian target, which is useful for testing endian-sensitive code.

Running Miri on CI

To run Miri on CI, make sure that you handle the case where the latest nightly does not ship the Miri component because it currently does not build. rustup toolchain install --component knows how to handle this situation, so the following snippet should always work:

rustup toolchain install nightly --component miri
rustup override set nightly

cargo miri test

Here is an example job for GitHub Actions:

  miri:
    name: "Miri"
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Install Miri
        run: |
          rustup toolchain install nightly --component miri
          rustup override set nightly
          cargo miri setup
      - name: Test with Miri
        run: cargo miri test

The explicit cargo miri setup helps to keep the output of the actual test step clean.

Testing for alignment issues

Miri can sometimes miss misaligned accesses since allocations can "happen to be" aligned just right. You can use -Zmiri-symbolic-alignment-check to definitely catch all such issues, but that flag will also cause false positives when code does manual pointer arithmetic to account for alignment. Another alternative is to call Miri with various values for -Zmiri-seed; that will alter the randomness that is used to determine allocation base addresses. The following snippet calls Miri in a loop with different values for the seed:

for SEED in $(seq 0 255); do
  echo "Trying seed: $SEED"
  MIRIFLAGS=-Zmiri-seed=$SEED cargo miri test || { echo "Failing seed: $SEED"; break; };
done

Supported targets

Miri does not support all targets supported by Rust. The good news, however, is that no matter your host OS/platform, it is easy to run code for any target using --target!

The following targets are tested on CI and thus should always work (to the degree documented below):

• All Rust Tier 1 targets are supported by Miri. They are all checked on Miri's CI, and some (at least one per OS) are even checked on every Rust PR, so the shipped Miri should always work on these targets.
• aarch64-apple-darwin is supported.
• s390x-unknown-linux-gnu is supported as our "big-endian target of choice".
• For every other target with OS linux, macos, or windows, Miri should generally work, but we make no promises and we don't run tests for such targets.
• For targets on other operating systems, even basic operations such as printing to the standard output might not work, and Miri might fail before even reaching the main function.

However, even for targets that we do support, the degree of support for accessing platform APIs (such as the file system) differs between targets: generally, Linux targets have the best support, and macOS targets are usually on par. Windows is supported less well.

Running tests in parallel

Though it implements Rust threading, Miri itself is a single-threaded interpreter. This means that when running cargo miri test, you will probably see a dramatic increase in the amount of time it takes to run your whole test suite due to the inherent interpreter slowdown and a loss of parallelism.

You can get your test suite's parallelism back by running cargo miri nextest run -jN (note that you will need cargo-nextest installed). This works because cargo-nextest collects a list of all tests then launches a separate cargo miri run for each test. You will need to specify a -j or --test-threads; by default cargo miri nextest run runs one test at a time. For more details, see the cargo-nextest Miri documentation.

Note: This one-test-per-process model means that cargo miri test is able to detect data races where two tests race on a shared resource, but cargo miri nextest run will not detect such races.

Note: cargo-nextest does not support doctests, see nextest-rs/nextest#16

Common Problems

When using the above instructions, you may encounter a number of confusing compiler errors.

"note: run with RUST_BACKTRACE=1 environment variable to display a backtrace"

You may see this when trying to get Miri to display a backtrace. By default, Miri doesn't expose any environment to the program, so running RUST_BACKTRACE=1 cargo miri test will not do what you expect.

To get a backtrace, you need to disable isolation using -Zmiri-disable-isolation:

RUST_BACKTRACE=1 MIRIFLAGS="-Zmiri-disable-isolation" cargo miri test

"found possibly newer version of crate std which <dependency> depends on"

Your build directory may contain artifacts from an earlier build that have/have not been built for Miri. Run cargo clean before switching from non-Miri to Miri builds and vice-versa.

"found crate std compiled by an incompatible version of rustc"

You may be running cargo miri with a different compiler version than the one used to build the custom libstd that Miri uses, and Miri failed to detect that. Try deleting ~/.cache/miri.

"no mir for std::rt::lang_start_internal"

This means the sysroot you are using was not compiled with Miri in mind. This should never happen when you use cargo miri because that takes care of setting up the sysroot. If you are using miri (the Miri driver) directly, see the contributors' guide for how to use ./miri to best do that.

Miri -Z flags and environment variables

Miri adds its own set of -Z flags, which are usually set via the MIRIFLAGS environment variable. We first document the most relevant and most commonly used flags:

• -Zmiri-compare-exchange-weak-failure-rate=<rate> changes the failure rate of compare_exchange_weak operations. The default is 0.8 (so 4 out of 5 weak ops will fail). You can change it to any value between 0.0 and 1.0, where 1.0 means it will always fail and 0.0 means it will never fail. Note than setting it to 1.0 will likely cause hangs, since it means programs using compare_exchange_weak cannot make progress.
• -Zmiri-disable-isolation disables host isolation. As a consequence, the program has access to host resources such as environment variables, file systems, and randomness.
• -Zmiri-disable-leak-backtraces disables backtraces reports for memory leaks. By default, a backtrace is captured for every allocation when it is created, just in case it leaks. This incurs some memory overhead to store data that is almost never used. This flag is implied by -Zmiri-ignore-leaks.
• -Zmiri-env-forward=<var> forwards the var environment variable to the interpreted program. Can be used multiple times to forward several variables. Execution will still be deterministic if the value of forwarded variables stays the same. Has no effect if -Zmiri-disable-isolation is set.
• -Zmiri-ignore-leaks disables the memory leak checker, and also allows some remaining threads to exist when the main thread exits.
• -Zmiri-isolation-error=<action> configures Miri's response to operations requiring host access while isolation is enabled. abort, hide, warn, and warn-nobacktrace are the supported actions. The default is to abort, which halts the machine. Some (but not all) operations also support continuing execution with a "permission denied" error being returned to the program. warn prints a full backtrace when that happens; warn-nobacktrace is less verbose. hide hides the warning entirely.
• -Zmiri-num-cpus states the number of available CPUs to be reported by miri. By default, the number of available CPUs is 1. Note that this flag does not affect how miri handles threads in any way.
• -Zmiri-permissive-provenance disables the warning for integer-to-pointer casts and ptr::from_exposed_addr. This will necessarily miss some bugs as those operations are not efficiently and accurately implementable in a sanitizer, but it will only miss bugs that concern memory/pointers which is subject to these operations.
• -Zmiri-preemption-rate configures the probability that at the end of a basic block, the active thread will be preempted. The default is 0.01 (i.e., 1%). Setting this to 0 disables preemption.
• -Zmiri-report-progress makes Miri print the current stacktrace every now and then, so you can tell what it is doing when a program just keeps running. You can customize how frequently the report is printed via -Zmiri-report-progress=<blocks>, which prints the report every N basic blocks.
• -Zmiri-seed=<num> configures the seed of the RNG that Miri uses to resolve non-determinism. This RNG is used to pick base addresses for allocations, to determine preemption and failure of compare_exchange_weak, and to control store buffering for weak memory emulation. When isolation is enabled (the default), this is also used to emulate system entropy. The default seed is 0. You can increase test coverage by running Miri multiple times with different seeds.
• -Zmiri-strict-provenance enables strict provenance checking in Miri. This means that casting an integer to a pointer yields a result with 'invalid' provenance, i.e., with provenance that cannot be used for any memory access.
• -Zmiri-symbolic-alignment-check makes the alignment check more strict. By default, alignment is checked by casting the pointer to an integer, and making sure that is a multiple of the alignment. This can lead to cases where a program passes the alignment check by pure chance, because things "happened to be" sufficiently aligned -- there is no UB in this execution but there would be UB in others. To avoid such cases, the symbolic alignment check only takes into account the requested alignment of the relevant allocation, and the offset into that allocation. This avoids missing such bugs, but it also incurs some false positives when the code does manual integer arithmetic to ensure alignment. (The standard library align_to method works fine in both modes; under symbolic alignment it only fills the middle slice when the allocation guarantees sufficient alignment.)

The remaining flags are for advanced use only, and more likely to change or be removed. Some of these are unsound, which means they can lead to Miri failing to detect cases of undefined behavior in a program.

• -Zmiri-disable-abi-check disables checking function ABI. Using this flag is unsound. This flag is deprecated.
• -Zmiri-disable-alignment-check disables checking pointer alignment, so you can focus on other failures, but it means Miri can miss bugs in your program. Using this flag is unsound.
• -Zmiri-disable-data-race-detector disables checking for data races. Using this flag is unsound. This implies -Zmiri-disable-weak-memory-emulation.
• -Zmiri-disable-stacked-borrows disables checking the experimental aliasing rules to track borrows (Stacked Borrows and Tree Borrows). This can make Miri run faster, but it also means no aliasing violations will be detected. Using this flag is unsound (but the affected soundness rules are experimental). Later flags take precedence: borrow tracking can be reactivated by -Zmiri-tree-borrows.
• -Zmiri-disable-validation disables enforcing validity invariants, which are enforced by default. This is mostly useful to focus on other failures (such as out-of-bounds accesses) first. Setting this flag means Miri can miss bugs in your program. However, this can also help to make Miri run faster. Using this flag is unsound.
• -Zmiri-disable-weak-memory-emulation disables the emulation of some C++11 weak memory effects.
• -Zmiri-extern-so-file=<path to a shared object file> is an experimental flag for providing support for FFI calls. Functions not provided by that file are still executed via the usual Miri shims. WARNING: If an invalid/incorrect .so file is specified, this can cause undefined behaviour in Miri itself! And of course, Miri cannot do any checks on the actions taken by the external code. Note that Miri has its own handling of file descriptors, so if you want to replace some functions working on file descriptors, you will have to replace all of them, or the two kinds of file descriptors will be mixed up. This is work in progress; currently, only integer arguments and return values are supported (and no, pointer/integer casts to work around this limitation will not work; they will fail horribly). It also only works on unix hosts for now. Follow the discussion on supporting other types.
• -Zmiri-measureme=<name> enables measureme profiling for the interpreted program. This can be used to find which parts of your program are executing slowly under Miri. The profile is written out to a file inside a directory called <name>, and can be processed using the tools in the repository https://github.com/rust-lang/measureme.
• -Zmiri-mute-stdout-stderr silently ignores all writes to stdout and stderr, but reports to the program that it did actually write. This is useful when you are not interested in the actual program's output, but only want to see Miri's errors and warnings.
• -Zmiri-panic-on-unsupported will makes some forms of unsupported functionality, such as FFI and unsupported syscalls, panic within the context of the emulated application instead of raising an error within the context of Miri (and halting execution). Note that code might not expect these operations to ever panic, so this flag can lead to strange (mis)behavior.
• -Zmiri-retag-fields[=<all|none|scalar>] controls when Stacked Borrows retagging recurses into fields. all means it always recurses (the default, and equivalent to -Zmiri-retag-fields without an explicit value), none means it never recurses, scalar means it only recurses for types where we would also emit noalias annotations in the generated LLVM IR (types passed as individual scalars or pairs of scalars). Setting this to none is unsound.
• -Zmiri-provenance-gc=<blocks> configures how often the pointer provenance garbage collector runs. The default is to search for and remove unreachable provenance once every 10000 basic blocks. Setting this to 0 disables the garbage collector, which causes some programs to have explosive memory usage and/or super-linear runtime.
• -Zmiri-track-alloc-id=<id1>,<id2>,... shows a backtrace when the given allocations are being allocated or freed. This helps in debugging memory leaks and use after free bugs. Specifying this argument multiple times does not overwrite the previous values, instead it appends its values to the list. Listing an id multiple times has no effect.
• -Zmiri-track-call-id=<id1>,<id2>,... shows a backtrace when the given call ids are assigned to a stack frame. This helps in debugging UB related to Stacked Borrows "protectors". Specifying this argument multiple times does not overwrite the previous values, instead it appends its values to the list. Listing an id multiple times has no effect.
• -Zmiri-track-pointer-tag=<tag1>,<tag2>,... shows a backtrace when a given pointer tag is created and when (if ever) it is popped from a borrow stack (which is where the tag becomes invalid and any future use of it will error). This helps you in finding out why UB is happening and where in your code would be a good place to look for it. Specifying this argument multiple times does not overwrite the previous values, instead it appends its values to the list. Listing a tag multiple times has no effect.
• -Zmiri-track-weak-memory-loads shows a backtrace when weak memory emulation returns an outdated value from a load. This can help diagnose problems that disappear under -Zmiri-disable-weak-memory-emulation.
• -Zmiri-tree-borrows replaces Stacked Borrows with the Tree Borrows rules. The soundness rules are already experimental without this flag, but even more so with this flag.
• -Zmiri-force-page-size=<num> overrides the default page size for an architecture, in multiples of 1k. 4 is default for most targets. This value should always be a power of 2 and nonzero.
• -Zmiri-unique-is-unique performs additional aliasing checks for core::ptr::Unique to ensure that it could theoretically be considered noalias. This flag is experimental and has an effect only when used with -Zmiri-tree-borrows.

Some native rustc -Z flags are also very relevant for Miri:

• -Zmir-opt-level controls how many MIR optimizations are performed. Miri overrides the default to be 0; be advised that using any higher level can make Miri miss bugs in your program because they got optimized away.
• -Zalways-encode-mir makes rustc dump MIR even for completely monomorphic functions. This is needed so that Miri can execute such functions, so Miri sets this flag per default.
• -Zmir-emit-retag controls whether Retag statements are emitted. Miri enables this per default because it is needed for Stacked Borrows and Tree Borrows.

Moreover, Miri recognizes some environment variables:

• MIRI_AUTO_OPS indicates whether the automatic execution of rustfmt, clippy and toolchain setup should be skipped. If it is set to no, they are skipped. This is used to allow automated IDE actions to avoid the auto ops.
• MIRI_LOG, MIRI_BACKTRACE control logging and backtrace printing during Miri executions, also see "Testing the Miri driver" in CONTRIBUTING.md.
• MIRIFLAGS (recognized by cargo miri and the test suite) defines extra flags to be passed to Miri.
• MIRI_LIB_SRC defines the directory where Miri expects the sources of the standard library that it will build and use for interpretation. This directory must point to the library subdirectory of a rust-lang/rust repository checkout. Note that changing files in that directory does not automatically trigger a re-build of the standard library; you have to clear the Miri build cache manually (on Linux, rm -rf ~/.cache/miri; on Windows, rmdir /S "%LOCALAPPDATA%\rust-lang\miri\cache"; and on macOS, rm -rf ~/Library/Caches/org.rust-lang.miri).
• MIRI_SYSROOT (recognized by cargo miri and the Miri driver) indicates the sysroot to use. When using cargo miri, this skips the automatic setup -- only set this if you do not want to use the automatically created sysroot. For directly invoking the Miri driver, this variable (or a --sysroot flag) is mandatory. When invoking cargo miri setup, this indicates where the sysroot will be put.
• MIRI_TEST_TARGET (recognized by the test suite and the ./miri script) indicates which target architecture to test against. miri and cargo miri accept the --target flag for the same purpose.
• MIRI_TEST_THREADS (recognized by the test suite): set the number of threads to use for running tests. By default the number of cores is used.
• MIRI_NO_STD (recognized by cargo miri) makes sure that the target's sysroot is built without libstd. This allows testing and running no_std programs. (Miri has a heuristic to detect no-std targets based on the target name; this environment variable is only needed when that heuristic fails.)
• RUSTC_BLESS (recognized by the test suite and cargo-miri-test/run-test.py): overwrite all stderr and stdout files instead of checking whether the output matches.
• MIRI_SKIP_UI_CHECKS (recognized by the test suite): don't check whether the stderr or stdout files match the actual output.

The following environment variables are internal and must not be used by anyone but Miri itself. They are used to communicate between different Miri binaries, and as such worth documenting:

• MIRI_BE_RUSTC can be set to host or target. It tells the Miri driver to actually not interpret the code but compile it like rustc would. With target, Miri sets some compiler flags to prepare the code for interpretation; with host, this is not done. This environment variable is useful to be sure that the compiled rlibs are compatible with Miri.
• MIRI_CALLED_FROM_SETUP is set during the Miri sysroot build, which will re-invoke cargo-miri as the rustc to use for this build.
• MIRI_CALLED_FROM_RUSTDOC when set to any value tells cargo-miri that it is running as a child process of rustdoc, which invokes it twice for each doc-test and requires special treatment, most notably a check-only build before interpretation. This is set by cargo-miri itself when running as a rustdoc-wrapper.
• MIRI_CWD when set to any value tells the Miri driver to change to the given directory after loading all the source files, but before commencing interpretation. This is useful if the interpreted program wants a different working directory at run-time than at build-time.
• MIRI_LOCAL_CRATES is set by cargo-miri to tell the Miri driver which crates should be given special treatment in diagnostics, in addition to the crate currently being compiled.
• MIRI_VERBOSE when set to any value tells the various cargo-miri phases to perform verbose logging.
• MIRI_HOST_SYSROOT is set by bootstrap to tell cargo-miri which sysroot to use for host operations.

Miri extern functions

Miri provides some extern functions that programs can import to access Miri-specific functionality. They are declared in /tests/utils/miri_extern.rs.

Contributing and getting help

If you want to contribute to Miri, great! Please check out our contribution guide.

For help with running Miri, you can open an issue here on GitHub or use the Miri stream on the Rust Zulip.

History

This project began as part of an undergraduate research course in 2015 by @solson at the University of Saskatchewan. There are slides and a report available from that project. In 2016, @oli-obk joined to prepare Miri for eventually being used as const evaluator in the Rust compiler itself (basically, for const and static stuff), replacing the old evaluator that worked directly on the AST. In 2017, @RalfJung did an internship with Mozilla and began developing Miri towards a tool for detecting undefined behavior, and also using Miri as a way to explore the consequences of various possible definitions for undefined behavior in Rust. @oli-obk's move of the Miri engine into the compiler finally came to completion in early 2018. Meanwhile, later that year, @RalfJung did a second internship, developing Miri further with support for checking basic type invariants and verifying that references are used according to their aliasing restrictions.

Bugs found by Miri

Miri has already found a number of bugs in the Rust standard library and beyond, which we collect here.

Definite bugs found:

• Debug for vec_deque::Iter accessing uninitialized memory
• Vec::into_iter doing an unaligned ZST read
• From<&[T]> for Rc creating a not sufficiently aligned reference
• BTreeMap creating a shared reference pointing to a too small allocation
• Vec::append creating a dangling reference
• Futures turning a shared reference into a mutable one
• str turning a shared reference into a mutable one
• rand performing unaligned reads
• The Unix allocator calling posix_memalign in an invalid way
• getrandom calling the getrandom syscall in an invalid way
• Vec and BTreeMap leaking memory under some (panicky) conditions
• beef leaking memory
• EbrCell using uninitialized memory incorrectly
• TiKV performing an unaligned pointer access
• servo_arc creating a dangling shared reference
• TiKV constructing out-of-bounds pointers (and overlapping mutable references)
• encoding_rs doing out-of-bounds pointer arithmetic
• TiKV using Vec::from_raw_parts incorrectly
• Incorrect doctests for AtomicPtr and Box::from_raw_in
• Insufficient alignment in ThinVec
• crossbeam-epoch calling assume_init on a partly-initialized MaybeUninit
• integer-encoding dereferencing a misaligned pointer
• rkyv constructing a Box<[u8]> from an overaligned allocation
• Data race in arc-swap
• Data race in thread::scope
• regex incorrectly handling unaligned Vec<u8> buffers
• Incorrect use of compare_exchange_weak in once_cell
• Dropping with unaligned pointers in vec::IntoIter
• Deallocating with the wrong layout in new specializations for in-place Iterator::collect

Violations of Stacked Borrows found that are likely bugs (but Stacked Borrows is currently just an experiment):

• VecDeque::drain creating overlapping mutable references
• Various BTreeMap problems
  • BTreeMap iterators creating mutable references that overlap with shared references
  • BTreeMap::iter_mut creating overlapping mutable references
  • BTreeMap node insertion using raw pointers outside their valid memory area
• LinkedList cursor insertion creating overlapping mutable references
• Vec::push invalidating existing references into the vector
• align_to_mut violating uniqueness of mutable references
• sized-chunks creating aliasing mutable references
• String::push_str invalidating existing references into the string
• ryu using raw pointers outside their valid memory area
• ink! creating overlapping mutable references
• TiKV creating overlapping mutable reference and raw pointer
• Windows Env iterator using a raw pointer outside its valid memory area
• VecDeque::iter_mut creating overlapping mutable references
• Various standard library aliasing issues involving raw pointers
• <[T]>::copy_within using a loan after invalidating it

Scientific papers employing Miri

• Stacked Borrows: An Aliasing Model for Rust
• Using Lightweight Formal Methods to Validate a Key-Value Storage Node in Amazon S3
• SyRust: Automatic Testing of Rust Libraries with Semantic-Aware Program Synthesis

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you shall be dual licensed as above, without any additional terms or conditions.