3 [![Actions build status][actions-badge]][actions-url]
5 [actions-badge]: https://github.com/rust-lang/miri/workflows/CI/badge.svg?branch=master
6 [actions-url]: https://github.com/rust-lang/miri/actions
8 An experimental interpreter for [Rust][rust]'s
9 [mid-level intermediate representation][mir] (MIR). It can run binaries and
10 test suites of cargo projects and detect certain classes of
11 [undefined behavior](https://doc.rust-lang.org/reference/behavior-considered-undefined.html),
14 * Out-of-bounds memory accesses and use-after-free
15 * Invalid use of uninitialized data
16 * Violation of intrinsic preconditions (an [`unreachable_unchecked`] being
17 reached, calling [`copy_nonoverlapping`] with overlapping ranges, ...)
18 * Not sufficiently aligned memory accesses and references
19 * Violation of *some* basic type invariants (a `bool` that is not 0 or 1, for example,
20 or an invalid enum discriminant)
21 * **Experimental**: Violations of the [Stacked Borrows] rules governing aliasing
23 * **Experimental**: Data races (but no weak memory effects)
25 On top of that, Miri will also tell you about memory leaks: when there is memory
26 still allocated at the end of the execution, and that memory is not reachable
27 from a global `static`, Miri will raise an error.
29 You can use Miri to emulate programs on other targets, e.g. to ensure that
30 byte-level data manipulation works correctly both on little-endian and
31 big-endian systems. See
32 [cross-interpretation](#cross-interpretation-running-for-different-targets)
35 Miri has already discovered some [real-world bugs](#bugs-found-by-miri). If you
36 found a bug with Miri, we'd appreciate if you tell us and we'll add it to the
39 However, be aware that Miri will **not catch all cases of undefined behavior**
40 in your program, and cannot run all programs:
42 * There are still plenty of open questions around the basic invariants for some
43 types and when these invariants even have to hold. Miri tries to avoid false
44 positives here, so if your program runs fine in Miri right now that is by no
45 means a guarantee that it is UB-free when these questions get answered.
47 In particular, Miri does currently not check that integers/floats are
48 initialized or that references point to valid data.
49 * If the program relies on unspecified details of how data is laid out, it will
50 still run fine in Miri -- but might break (including causing UB) on different
51 compiler versions or different platforms.
52 * Program execution is non-deterministic when it depends, for example, on where
53 exactly in memory allocations end up, or on the exact interleaving of
54 concurrent threads. Miri tests one of many possible executions of your
55 program. You can alleviate this to some extent by running Miri with different
56 values for `-Zmiri-seed`, but that will still by far not explore all possible
58 * Miri runs the program as a platform-independent interpreter, so the program
59 has no access to most platform-specific APIs or FFI. A few APIs have been
60 implemented (such as printing to stdout, accessing environment variables, and
61 basic file system access) but most have not: for example, Miri currently does
62 not support networking. System API support varies between targets; if you run
63 on Windows it is a good idea to use `--target x86_64-unknown-linux-gnu` to get
65 * Threading support is not finished yet. E.g., weak memory effects are not
66 emulated and spin loops (without syscalls) just loop forever. There is no
67 threading support on Windows.
69 [rust]: https://www.rust-lang.org/
70 [mir]: https://github.com/rust-lang/rfcs/blob/master/text/1211-mir.md
71 [`unreachable_unchecked`]: https://doc.rust-lang.org/stable/std/hint/fn.unreachable_unchecked.html
72 [`copy_nonoverlapping`]: https://doc.rust-lang.org/stable/std/ptr/fn.copy_nonoverlapping.html
73 [Stacked Borrows]: https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md
78 Install Miri on Rust nightly via `rustup`:
81 rustup +nightly component add miri
84 If `rustup` says the `miri` component is unavailable, that's because not all
85 nightly releases come with all tools. Check out
86 [this website](https://rust-lang.github.io/rustup-components-history) to
87 determine a nightly version that comes with Miri and install that using `rustup
88 toolchain install nightly-YYYY-MM-DD`. Either way, all of the following commands
89 assume the right toolchain is pinned via `rustup override set nightly` or
90 `rustup override set nightly-YYYY-MM-DD`. (Alternatively, use `cargo
91 +nightly`/`cargo +nightly-YYYY-MM-DD` for each of the following commands.)
93 Now you can run your project in Miri:
95 1. Run `cargo clean` to eliminate any cached dependencies. Miri needs your
96 dependencies to be compiled the right way, that would not happen if they have
97 previously already been compiled.
98 2. To run all tests in your project through Miri, use `cargo miri test`.
99 3. If you have a binary project, you can run it through Miri using `cargo miri run`.
101 The first time you run Miri, it will perform some extra setup and install some
102 dependencies. It will ask you for confirmation before installing anything.
104 `cargo miri run/test` supports the exact same flags as `cargo run/test`. For
105 example, `cargo miri test filter` only runs the tests containing `filter` in
108 You can pass arguments to Miri via `MIRIFLAGS`. For example,
109 `MIRIFLAGS="-Zmiri-disable-stacked-borrows" cargo miri run` runs the program
110 without checking the aliasing of references.
112 When compiling code via `cargo miri`, the `cfg(miri)` config flag is set for code
113 that will be interpret under Miri. You can use this to ignore test cases that fail
114 under Miri because they do things Miri does not support:
118 #[cfg_attr(miri, ignore)]
119 fn does_not_work_on_miri() {
120 tokio::run(futures::future::ok::<_, ()>(()));
124 There is no way to list all the infinite things Miri cannot do, but the
125 interpreter will explicitly tell you when it finds something unsupported:
128 error: unsupported operation: can't call foreign function: bind
130 = help: this is likely not a bug in the program; it indicates that the program \
131 performed an operation that the interpreter does not support
134 ### Cross-interpretation: running for different targets
136 Miri can not only run a binary or test suite for your host target, it can also
137 perform cross-interpretation for arbitrary foreign targets: `cargo miri run
138 --target x86_64-unknown-linux-gnu` will run your program as if it was a Linux
139 program, no matter your host OS. This is particularly useful if you are using
140 Windows, as the Linux target is much better supported than Windows targets.
142 You can also use this to test platforms with different properties than your host
143 platform. For example `cargo miri test --target mips64-unknown-linux-gnuabi64`
144 will run your test suite on a big-endian target, which is useful for testing
145 endian-sensitive code.
147 ### Running Miri on CI
149 To run Miri on CI, make sure that you handle the case where the latest nightly
150 does not ship the Miri component because it currently does not build. `rustup
151 toolchain install --component` knows how to handle this situation, so the
152 following snippet should always work:
155 rustup toolchain install nightly --component miri
156 rustup override set nightly
161 Here is an example job for GitHub Actions:
166 runs-on: ubuntu-latest
168 - uses: actions/checkout@v3
171 rustup toolchain install nightly --component miri
172 rustup override set nightly
174 - name: Test with Miri
178 The explicit `cargo miri setup` helps to keep the output of the actual test step
181 ### Testing for alignment issues
183 Miri can sometimes miss misaligned accesses since allocations can "happen to be"
184 aligned just right. You can use `-Zmiri-symbolic-alignment-check` to definitely
185 catch all such issues, but that flag will also cause false positives when code
186 does manual pointer arithmetic to account for alignment. Another alternative is
187 to call Miri with various values for `-Zmiri-seed`; that will alter the
188 randomness that is used to determine allocation base addresses. The following
189 snippet calls Miri in a loop with different values for the seed:
192 for seed in $({ echo obase=16; seq 255; } | bc); do
193 MIRIFLAGS=-Zmiri-seed=$seed cargo miri test || { echo "Last seed: $seed"; break; };
197 ### Supported targets
199 Miri does not support all targets supported by Rust. The good news, however, is
200 that no matter your host OS/platform, it is easy to run code for *any* target
203 The following targets are tested on CI and thus should always work (to the
204 degree documented below):
206 - The best-supported target is `x86_64-unknown-linux-gnu`. Miri releases are
207 blocked on things working with this target. Most other Linux targets should
208 also work well; we do run the test suite on `i686-unknown-linux-gnu` as a
209 32bit target and `mips64-unknown-linux-gnuabi64` as a big-endian target.
210 - `x86_64-apple-darwin` should work basically as well as Linux. We also test
211 `aarch64-apple-darwin`. However, we might ship Miri with a nightly even when
212 some features on these targets regress.
213 - `x86_64-pc-windows-msvc` works, but supports fewer features than the Linux and
214 Apple targets. For example, file system access and concurrency are not
215 supported on Windows. We also test `i686-pc-windows-msvc`, with the same
216 reduced feature set. We might ship Miri with a nightly even when some features
217 on these targets regress.
221 When using the above instructions, you may encounter a number of confusing compiler
224 #### "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace"
226 You may see this when trying to get Miri to display a backtrace. By default, Miri
227 doesn't expose any environment to the program, so running
228 `RUST_BACKTRACE=1 cargo miri test` will not do what you expect.
230 To get a backtrace, you need to disable isolation
231 [using `-Zmiri-disable-isolation`][miri-flags]:
234 RUST_BACKTRACE=1 MIRIFLAGS="-Zmiri-disable-isolation" cargo miri test
237 #### "found possibly newer version of crate `std` which `<dependency>` depends on"
239 Your build directory may contain artifacts from an earlier build that have/have
240 not been built for Miri. Run `cargo clean` before switching from non-Miri to
241 Miri builds and vice-versa.
243 #### "found crate `std` compiled by an incompatible version of rustc"
245 You may be running `cargo miri` with a different compiler version than the one
246 used to build the custom libstd that Miri uses, and Miri failed to detect that.
247 Try deleting `~/.cache/miri`.
249 #### "no mir for `std::rt::lang_start_internal`"
251 This means the sysroot you are using was not compiled with Miri in mind. This
252 should never happen when you use `cargo miri` because that takes care of setting
253 up the sysroot. If you are using `miri` (the Miri driver) directly, see the
254 [contributors' guide](CONTRIBUTING.md) for how to use `./miri` to best do that.
257 ## Miri `-Z` flags and environment variables
258 [miri-flags]: #miri--z-flags-and-environment-variables
260 Miri adds its own set of `-Z` flags, which are usually set via the `MIRIFLAGS`
261 environment variable. We first document the most relevant and most commonly used flags:
263 * `-Zmiri-compare-exchange-weak-failure-rate=<rate>` changes the failure rate of
264 `compare_exchange_weak` operations. The default is `0.8` (so 4 out of 5 weak ops will fail).
265 You can change it to any value between `0.0` and `1.0`, where `1.0` means it
266 will always fail and `0.0` means it will never fail.
267 * `-Zmiri-disable-isolation` disables host isolation. As a consequence,
268 the program has access to host resources such as environment variables, file
269 systems, and randomness.
270 * `-Zmiri-isolation-error=<action>` configures Miri's response to operations
271 requiring host access while isolation is enabled. `abort`, `hide`, `warn`,
272 and `warn-nobacktrace` are the supported actions. The default is to `abort`,
273 which halts the machine. Some (but not all) operations also support continuing
274 execution with a "permission denied" error being returned to the program.
275 `warn` prints a full backtrace when that happen; `warn-nobacktrace` is less
276 verbose. `hide` hides the warning entirely.
277 * `-Zmiri-env-exclude=<var>` keeps the `var` environment variable isolated from the host so that it
278 cannot be accessed by the program. Can be used multiple times to exclude several variables. The
279 `TERM` environment variable is excluded by default to [speed up the test
280 harness](https://github.com/rust-lang/miri/issues/1702). This has no effect unless
281 `-Zmiri-disable-isolation` is also set.
282 * `-Zmiri-env-forward=<var>` forwards the `var` environment variable to the interpreted program. Can
283 be used multiple times to forward several variables. This has no effect if
284 `-Zmiri-disable-isolation` is set.
285 * `-Zmiri-ignore-leaks` disables the memory leak checker, and also allows some
286 remaining threads to exist when the main thread exits.
287 * `-Zmiri-seed=<hex>` configures the seed of the RNG that Miri uses to resolve
288 non-determinism. This RNG is used to pick base addresses for allocations. When
289 isolation is enabled (the default), this is also used to emulate system
290 entropy. The default seed is 0. You can increase test coverage by running Miri
291 multiple times with different seeds.
292 **NOTE**: This entropy is not good enough for cryptographic use! Do not
293 generate secret keys in Miri or perform other kinds of cryptographic
294 operations that rely on proper random numbers.
295 * `-Zmiri-strict-provenance` enables [strict
296 provenance](https://github.com/rust-lang/rust/issues/95228) checking in Miri. This means that
297 casting an integer to a pointer yields a result with 'invalid' provenance, i.e., with provenance
298 that cannot be used for any memory access. Also implies `-Zmiri-tag-raw-pointers` and
299 `-Zmiri-check-number-validity`.
301 The remaining flags are for advanced use only, and more likely to change or be removed.
302 Some of these are **unsound**, which means they can lead
303 to Miri failing to detect cases of undefined behavior in a program.
305 * `-Zmiri-check-number-validity` enables checking of integer and float validity
306 (e.g., they must be initialized and not carry pointer provenance) as part of
307 enforcing validity invariants. This has no effect when
308 `-Zmiri-disable-validation` is present.
309 * `-Zmiri-disable-abi-check` disables checking [function ABI]. Using this flag
311 * `-Zmiri-disable-alignment-check` disables checking pointer alignment, so you
312 can focus on other failures, but it means Miri can miss bugs in your program.
313 Using this flag is **unsound**.
314 * `-Zmiri-disable-data-race-detector` disables checking for data races. Using
315 this flag is **unsound**.
316 * `-Zmiri-disable-stacked-borrows` disables checking the experimental
317 [Stacked Borrows] aliasing rules. This can make Miri run faster, but it also
318 means no aliasing violations will be detected. Using this flag is **unsound**
319 (but the affected soundness rules are experimental).
320 * `-Zmiri-disable-validation` disables enforcing validity invariants, which are
321 enforced by default. This is mostly useful to focus on other failures (such
322 as out-of-bounds accesses) first. Setting this flag means Miri can miss bugs
323 in your program. However, this can also help to make Miri run faster. Using
324 this flag is **unsound**.
325 * `-Zmiri-measureme=<name>` enables `measureme` profiling for the interpreted program.
326 This can be used to find which parts of your program are executing slowly under Miri.
327 The profile is written out to a file with the prefix `<name>`, and can be processed
328 using the tools in the repository https://github.com/rust-lang/measureme.
329 * `-Zmiri-mute-stdout-stderr` silently ignores all writes to stdout and stderr,
330 but reports to the program that it did actually write. This is useful when you
331 are not interested in the actual program's output, but only want to see Miri's
333 * `-Zmiri-panic-on-unsupported` will makes some forms of unsupported functionality,
334 such as FFI and unsupported syscalls, panic within the context of the emulated
335 application instead of raising an error within the context of Miri (and halting
336 execution). Note that code might not expect these operations to ever panic, so
337 this flag can lead to strange (mis)behavior.
338 * `-Zmiri-permissive-provenance` is **experimental**. This will make Miri do a
339 best-effort attempt to implement the semantics of
340 [`expose_addr`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.expose_addr)
342 [`ptr::from_exposed_addr`](https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html)
343 for pointer-to-int and int-to-pointer casts, respectively. This will
344 necessarily miss some bugs as those semantics are not efficiently
345 implementable in a sanitizer, but it will only miss bugs that concerns
346 memory/pointers which is subject to these operations. Also note that this flag
347 is currently incompatible with Stacked Borrows, so you will have to also pass
348 `-Zmiri-disable-stacked-borrows` to use this.
349 * `-Zmiri-symbolic-alignment-check` makes the alignment check more strict. By
350 default, alignment is checked by casting the pointer to an integer, and making
351 sure that is a multiple of the alignment. This can lead to cases where a
352 program passes the alignment check by pure chance, because things "happened to
353 be" sufficiently aligned -- there is no UB in this execution but there would
354 be UB in others. To avoid such cases, the symbolic alignment check only takes
355 into account the requested alignment of the relevant allocation, and the
356 offset into that allocation. This avoids missing such bugs, but it also
357 incurs some false positives when the code does manual integer arithmetic to
358 ensure alignment. (The standard library `align_to` method works fine in both
359 modes; under symbolic alignment it only fills the middle slice when the
360 allocation guarantees sufficient alignment.)
361 * `-Zmiri-track-alloc-id=<id1>,<id2>,...` shows a backtrace when the given allocations are
362 being allocated or freed. This helps in debugging memory leaks and
363 use after free bugs. Specifying this argument multiple times does not overwrite the previous
364 values, instead it appends its values to the list. Listing an id multiple times has no effect.
365 * `-Zmiri-track-call-id=<id1>,<id2>,...` shows a backtrace when the given call ids are
366 assigned to a stack frame. This helps in debugging UB related to Stacked
367 Borrows "protectors". Specifying this argument multiple times does not overwrite the previous
368 values, instead it appends its values to the list. Listing an id multiple times has no effect.
369 * `-Zmiri-track-pointer-tag=<tag1>,<tag2>,...` shows a backtrace when a given pointer tag
370 is popped from a borrow stack (which is where the tag becomes invalid and any
371 future use of it will error). This helps you in finding out why UB is
372 happening and where in your code would be a good place to look for it.
373 Specifying this argument multiple times does not overwrite the previous
374 values, instead it appends its values to the list. Listing a tag multiple times has no effect.
375 * `-Zmiri-tag-raw-pointers` makes Stacked Borrows assign proper tags even for raw pointers. This can
376 make valid code using int-to-ptr casts fail to pass the checks, but also can help identify latent
377 aliasing issues in code that Miri accepts by default. You can recognize false positives by
378 `<untagged>` occurring in the message -- this indicates a pointer that was cast from an integer,
379 so Miri was unable to track this pointer. Note that it is not currently guaranteed that code that
380 works with `-Zmiri-tag-raw-pointers` also works without `-Zmiri-tag-raw-pointers`, but for the
381 vast majority of code, this will be the case.
383 [function ABI]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
385 Some native rustc `-Z` flags are also very relevant for Miri:
387 * `-Zmir-opt-level` controls how many MIR optimizations are performed. Miri
388 overrides the default to be `0`; be advised that using any higher level can
389 make Miri miss bugs in your program because they got optimized away.
390 * `-Zalways-encode-mir` makes rustc dump MIR even for completely monomorphic
391 functions. This is needed so that Miri can execute such functions, so Miri
392 sets this flag per default.
393 * `-Zmir-emit-retag` controls whether `Retag` statements are emitted. Miri
394 enables this per default because it is needed for [Stacked Borrows].
396 Moreover, Miri recognizes some environment variables:
398 * `MIRI_LOG`, `MIRI_BACKTRACE` control logging and backtrace printing during
399 Miri executions, also [see "Testing the Miri driver" in `CONTRIBUTING.md`][testing-miri].
400 * `MIRIFLAGS` (recognized by `cargo miri` and the test suite) defines extra
401 flags to be passed to Miri.
402 * `MIRI_LIB_SRC` defines the directory where Miri expects the sources of the
403 standard library that it will build and use for interpretation. This directory
404 must point to the `library` subdirectory of a `rust-lang/rust` repository
405 checkout. Note that changing files in that directory does not automatically
406 trigger a re-build of the standard library; you have to clear the Miri build
407 cache manually (on Linux, `rm -rf ~/.cache/miri`).
408 * `MIRI_SYSROOT` (recognized by `cargo miri` and the test suite) indicates the
409 sysroot to use. Only set this if you do not want to use the automatically
410 created sysroot. (The `miri` driver sysroot is controlled via the `--sysroot`
412 * `MIRI_TEST_TARGET` (recognized by the test suite) indicates which target
413 architecture to test against. `miri` and `cargo miri` accept the `--target`
414 flag for the same purpose.
415 * `MIRI_BLESS` (recognized by the test suite) overwrite all `stderr` and `stdout` files
416 instead of checking whether the output matches.
417 * `MIRI_SKIP_UI_CHECKS` (recognized by the test suite) don't check whether the
418 `stderr` or `stdout` files match the actual output. Useful for the rustc test suite
419 which has subtle differences that we don't care about.
421 The following environment variables are *internal* and must not be used by
422 anyone but Miri itself. They are used to communicate between different Miri
423 binaries, and as such worth documenting:
425 * `MIRI_BE_RUSTC` can be set to `host` or `target`. It tells the Miri driver to
426 actually not interpret the code but compile it like rustc would. With `target`, Miri sets
427 some compiler flags to prepare the code for interpretation; with `host`, this is not done.
428 This environment variable is useful to be sure that the compiled `rlib`s are compatible
430 * `MIRI_CALLED_FROM_XARGO` is set during the Miri-induced `xargo` sysroot build,
431 which will re-invoke `cargo-miri` as the `rustc` to use for this build.
432 * `MIRI_CALLED_FROM_RUSTDOC` when set to any value tells `cargo-miri` that it is
433 running as a child process of `rustdoc`, which invokes it twice for each doc-test
434 and requires special treatment, most notably a check-only build before interpretation.
435 This is set by `cargo-miri` itself when running as a `rustdoc`-wrapper.
436 * `MIRI_CWD` when set to any value tells the Miri driver to change to the given
437 directory after loading all the source files, but before commencing
438 interpretation. This is useful if the interpreted program wants a different
439 working directory at run-time than at build-time.
440 * `MIRI_LOCAL_CRATES` is set by `cargo-miri` to tell the Miri driver which
441 crates should be given special treatment in diagnostics, in addition to the
442 crate currently being compiled.
443 * `MIRI_VERBOSE` when set to any value tells the various `cargo-miri` phases to
444 perform verbose logging.
446 [testing-miri]: CONTRIBUTING.md#testing-the-miri-driver
448 ## Miri `extern` functions
450 Miri provides some `extern` functions that programs can import to access
451 Miri-specific functionality:
456 /// Miri-provided extern function to mark the block `ptr` points to as a "root"
457 /// for some static memory. This memory and everything reachable by it is not
458 /// considered leaking even if it still exists when the program terminates.
460 /// `ptr` has to point to the beginning of an allocated block.
461 fn miri_static_root(ptr: *const u8);
463 // Miri-provided extern function to get the amount of frames in the current backtrace.
464 // The `flags` argument must be `0`.
465 fn miri_backtrace_size(flags: u64) -> usize;
467 /// Miri-provided extern function to obtain a backtrace of the current call stack.
468 /// This writes a slice of pointers into `buf` - each pointer is an opaque value
469 /// that is only useful when passed to `miri_resolve_frame`.
470 /// `buf` must have `miri_backtrace_size(0) * pointer_size` bytes of space.
471 /// The `flags` argument must be `1`.
472 fn miri_get_backtrace(flags: u64, buf: *mut *mut ());
474 /// Miri-provided extern function to resolve a frame pointer obtained
475 /// from `miri_get_backtrace`. The `flags` argument must be `1`,
476 /// and `MiriFrame` should be declared as follows:
480 /// struct MiriFrame {
481 /// // The size of the name of the function being executed, encoded in UTF-8
483 /// // The size of filename of the function being executed, encoded in UTF-8
484 /// filename_len: usize,
485 /// // The line number currently being executed in `filename`, starting from '1'.
487 /// // The column number currently being executed in `filename`, starting from '1'.
489 /// // The function pointer to the function currently being executed.
490 /// // This can be compared against function pointers obtained by
491 /// // casting a function (e.g. `my_fn as *mut ()`)
496 /// The fields must be declared in exactly the same order as they appear in `MiriFrame` above.
497 /// This function can be called on any thread (not just the one which obtained `frame`).
498 fn miri_resolve_frame(frame: *mut (), flags: u64) -> MiriFrame;
500 /// Miri-provided extern function to get the name and filename of the frame provided by `miri_resolve_frame`.
501 /// `name_buf` and `filename_buf` should be allocated with the `name_len` and `filename_len` fields of `MiriFrame`.
502 /// The flags argument must be `0`.
503 fn miri_resolve_frame_names(ptr: *mut (), flags: u64, name_buf: *mut u8, filename_buf: *mut u8);
505 /// Miri-provided extern function to begin unwinding with the given payload.
507 /// This is internal and unstable and should not be used; we give it here
508 /// just to be complete.
509 fn miri_start_panic(payload: *mut u8) -> !;
513 ## Contributing and getting help
515 If you want to contribute to Miri, great! Please check out our
516 [contribution guide](CONTRIBUTING.md).
518 For help with running Miri, you can open an issue here on
519 GitHub or use the [Miri stream on the Rust Zulip][zulip].
521 [zulip]: https://rust-lang.zulipchat.com/#narrow/stream/269128-miri
525 This project began as part of an undergraduate research course in 2015 by
526 @solson at the [University of Saskatchewan][usask]. There are [slides] and a
527 [report] available from that project. In 2016, @oli-obk joined to prepare Miri
528 for eventually being used as const evaluator in the Rust compiler itself
529 (basically, for `const` and `static` stuff), replacing the old evaluator that
530 worked directly on the AST. In 2017, @RalfJung did an internship with Mozilla
531 and began developing Miri towards a tool for detecting undefined behavior, and
532 also using Miri as a way to explore the consequences of various possible
533 definitions for undefined behavior in Rust. @oli-obk's move of the Miri engine
534 into the compiler finally came to completion in early 2018. Meanwhile, later
535 that year, @RalfJung did a second internship, developing Miri further with
536 support for checking basic type invariants and verifying that references are
537 used according to their aliasing restrictions.
539 [usask]: https://www.usask.ca/
540 [slides]: https://solson.me/miri-slides.pdf
541 [report]: https://solson.me/miri-report.pdf
543 ## Bugs found by Miri
545 Miri has already found a number of bugs in the Rust standard library and beyond, which we collect here.
549 * [`Debug for vec_deque::Iter` accessing uninitialized memory](https://github.com/rust-lang/rust/issues/53566)
550 * [`Vec::into_iter` doing an unaligned ZST read](https://github.com/rust-lang/rust/pull/53804)
551 * [`From<&[T]> for Rc` creating a not sufficiently aligned reference](https://github.com/rust-lang/rust/issues/54908)
552 * [`BTreeMap` creating a shared reference pointing to a too small allocation](https://github.com/rust-lang/rust/issues/54957)
553 * [`Vec::append` creating a dangling reference](https://github.com/rust-lang/rust/pull/61082)
554 * [Futures turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/56319)
555 * [`str` turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/58200)
556 * [`rand` performing unaligned reads](https://github.com/rust-random/rand/issues/779)
557 * [The Unix allocator calling `posix_memalign` in an invalid way](https://github.com/rust-lang/rust/issues/62251)
558 * [`getrandom` calling the `getrandom` syscall in an invalid way](https://github.com/rust-random/getrandom/pull/73)
559 * [`Vec`](https://github.com/rust-lang/rust/issues/69770) and [`BTreeMap`](https://github.com/rust-lang/rust/issues/69769) leaking memory under some (panicky) conditions
560 * [`beef` leaking memory](https://github.com/maciejhirsz/beef/issues/12)
561 * [`EbrCell` using uninitialized memory incorrectly](https://github.com/Firstyear/concread/commit/b15be53b6ec076acb295a5c0483cdb4bf9be838f#diff-6282b2fc8e98bd089a1f0c86f648157cR229)
562 * [TiKV performing an unaligned pointer access](https://github.com/tikv/tikv/issues/7613)
563 * [`servo_arc` creating a dangling shared reference](https://github.com/servo/servo/issues/26357)
564 * [TiKV constructing out-of-bounds pointers (and overlapping mutable references)](https://github.com/tikv/tikv/pull/7751)
565 * [`encoding_rs` doing out-of-bounds pointer arithmetic](https://github.com/hsivonen/encoding_rs/pull/53)
566 * [TiKV using `Vec::from_raw_parts` incorrectly](https://github.com/tikv/agatedb/pull/24)
567 * Incorrect doctests for [`AtomicPtr`](https://github.com/rust-lang/rust/pull/84052) and [`Box::from_raw_in`](https://github.com/rust-lang/rust/pull/84053)
568 * [Insufficient alignment in `ThinVec`](https://github.com/Gankra/thin-vec/pull/27)
569 * [`crossbeam-epoch` calling `assume_init` on a partly-initialized `MaybeUninit`](https://github.com/crossbeam-rs/crossbeam/pull/779)
570 * [`integer-encoding` dereferencing a misaligned pointer](https://github.com/dermesser/integer-encoding-rs/pull/23)
571 * [`rkyv` constructing a `Box<[u8]>` from an overaligned allocation](https://github.com/rkyv/rkyv/commit/a9417193a34757e12e24263178be8b2eebb72456)
573 Violations of [Stacked Borrows] found that are likely bugs (but Stacked Borrows is currently just an experiment):
575 * [`VecDeque::drain` creating overlapping mutable references](https://github.com/rust-lang/rust/pull/56161)
576 * Various `BTreeMap` problems
577 * [`BTreeMap` iterators creating mutable references that overlap with shared references](https://github.com/rust-lang/rust/pull/58431)
578 * [`BTreeMap::iter_mut` creating overlapping mutable references](https://github.com/rust-lang/rust/issues/73915)
579 * [`BTreeMap` node insertion using raw pointers outside their valid memory area](https://github.com/rust-lang/rust/issues/78477)
580 * [`LinkedList` cursor insertion creating overlapping mutable references](https://github.com/rust-lang/rust/pull/60072)
581 * [`Vec::push` invalidating existing references into the vector](https://github.com/rust-lang/rust/issues/60847)
582 * [`align_to_mut` violating uniqueness of mutable references](https://github.com/rust-lang/rust/issues/68549)
583 * [`sized-chunks` creating aliasing mutable references](https://github.com/bodil/sized-chunks/issues/8)
584 * [`String::push_str` invalidating existing references into the string](https://github.com/rust-lang/rust/issues/70301)
585 * [`ryu` using raw pointers outside their valid memory area](https://github.com/dtolnay/ryu/issues/24)
586 * [ink! creating overlapping mutable references](https://github.com/rust-lang/miri/issues/1364)
587 * [TiKV creating overlapping mutable reference and raw pointer](https://github.com/tikv/tikv/pull/7709)
588 * [Windows `Env` iterator using a raw pointer outside its valid memory area](https://github.com/rust-lang/rust/pull/70479)
589 * [`VecDeque::iter_mut` creating overlapping mutable references](https://github.com/rust-lang/rust/issues/74029)
590 * [Various standard library aliasing issues involving raw pointers](https://github.com/rust-lang/rust/pull/78602)
591 * [`<[T]>::copy_within` using a loan after invalidating it](https://github.com/rust-lang/rust/pull/85610)
593 ## Scientific papers employing Miri
595 * [Stacked Borrows: An Aliasing Model for Rust](https://plv.mpi-sws.org/rustbelt/stacked-borrows/)
596 * [Using Lightweight Formal Methods to Validate a Key-Value Storage Node in Amazon S3](https://www.amazon.science/publications/using-lightweight-formal-methods-to-validate-a-key-value-storage-node-in-amazon-s3)
597 * [SyRust: Automatic Testing of Rust Libraries with Semantic-Aware Program Synthesis](https://dl.acm.org/doi/10.1145/3453483.3454084)
601 Licensed under either of
603 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
604 http://www.apache.org/licenses/LICENSE-2.0)
605 * MIT license ([LICENSE-MIT](LICENSE-MIT) or
606 http://opensource.org/licenses/MIT)
612 Unless you explicitly state otherwise, any contribution intentionally submitted
613 for inclusion in the work by you shall be dual licensed as above, without any
614 additional terms or conditions.