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
24 * **Experimental**: Emulation of weak memory effects (i.e., reads can return outdated values)
26 On top of that, Miri will also tell you about memory leaks: when there is memory
27 still allocated at the end of the execution, and that memory is not reachable
28 from a global `static`, Miri will raise an error.
30 You can use Miri to emulate programs on other targets, e.g. to ensure that
31 byte-level data manipulation works correctly both on little-endian and
32 big-endian systems. See
33 [cross-interpretation](#cross-interpretation-running-for-different-targets)
36 Miri has already discovered some [real-world bugs](#bugs-found-by-miri). If you
37 found a bug with Miri, we'd appreciate if you tell us and we'll add it to the
40 However, be aware that Miri will **not catch all cases of undefined behavior**
41 in your program, and cannot run all programs:
43 * There are still plenty of open questions around the basic invariants for some
44 types and when these invariants even have to hold. Miri tries to avoid false
45 positives here, so if your program runs fine in Miri right now that is by no
46 means a guarantee that it is UB-free when these questions get answered.
48 In particular, Miri does currently not check 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. spin loops (without syscalls) just
66 loop forever. There is no threading support on Windows.
67 * Weak memory emulation may produce weak behaivours unobservable by compiled
68 programs running on real hardware when `SeqCst` fences are used, and it cannot
69 produce all behaviors possibly observable on real hardware.
71 [rust]: https://www.rust-lang.org/
72 [mir]: https://github.com/rust-lang/rfcs/blob/master/text/1211-mir.md
73 [`unreachable_unchecked`]: https://doc.rust-lang.org/stable/std/hint/fn.unreachable_unchecked.html
74 [`copy_nonoverlapping`]: https://doc.rust-lang.org/stable/std/ptr/fn.copy_nonoverlapping.html
75 [Stacked Borrows]: https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md
80 Install Miri on Rust nightly via `rustup`:
83 rustup +nightly component add miri
86 If `rustup` says the `miri` component is unavailable, that's because not all
87 nightly releases come with all tools. Check out
88 [this website](https://rust-lang.github.io/rustup-components-history) to
89 determine a nightly version that comes with Miri and install that using `rustup
90 toolchain install nightly-YYYY-MM-DD`. Either way, all of the following commands
91 assume the right toolchain is pinned via `rustup override set nightly` or
92 `rustup override set nightly-YYYY-MM-DD`. (Alternatively, use `cargo
93 +nightly`/`cargo +nightly-YYYY-MM-DD` for each of the following commands.)
95 Now you can run your project in Miri:
97 1. Run `cargo clean` to eliminate any cached dependencies. Miri needs your
98 dependencies to be compiled the right way, that would not happen if they have
99 previously already been compiled.
100 2. To run all tests in your project through Miri, use `cargo miri test`.
101 3. If you have a binary project, you can run it through Miri using `cargo miri run`.
103 The first time you run Miri, it will perform some extra setup and install some
104 dependencies. It will ask you for confirmation before installing anything.
106 `cargo miri run/test` supports the exact same flags as `cargo run/test`. For
107 example, `cargo miri test filter` only runs the tests containing `filter` in
110 You can pass arguments to Miri via `MIRIFLAGS`. For example,
111 `MIRIFLAGS="-Zmiri-disable-stacked-borrows" cargo miri run` runs the program
112 without checking the aliasing of references.
114 When compiling code via `cargo miri`, the `cfg(miri)` config flag is set for code
115 that will be interpret under Miri. You can use this to ignore test cases that fail
116 under Miri because they do things Miri does not support:
120 #[cfg_attr(miri, ignore)]
121 fn does_not_work_on_miri() {
122 tokio::run(futures::future::ok::<_, ()>(()));
126 There is no way to list all the infinite things Miri cannot do, but the
127 interpreter will explicitly tell you when it finds something unsupported:
130 error: unsupported operation: can't call foreign function: bind
132 = help: this is likely not a bug in the program; it indicates that the program \
133 performed an operation that the interpreter does not support
136 ### Cross-interpretation: running for different targets
138 Miri can not only run a binary or test suite for your host target, it can also
139 perform cross-interpretation for arbitrary foreign targets: `cargo miri run
140 --target x86_64-unknown-linux-gnu` will run your program as if it was a Linux
141 program, no matter your host OS. This is particularly useful if you are using
142 Windows, as the Linux target is much better supported than Windows targets.
144 You can also use this to test platforms with different properties than your host
145 platform. For example `cargo miri test --target mips64-unknown-linux-gnuabi64`
146 will run your test suite on a big-endian target, which is useful for testing
147 endian-sensitive code.
149 ### Running Miri on CI
151 To run Miri on CI, make sure that you handle the case where the latest nightly
152 does not ship the Miri component because it currently does not build. `rustup
153 toolchain install --component` knows how to handle this situation, so the
154 following snippet should always work:
157 rustup toolchain install nightly --component miri
158 rustup override set nightly
163 Here is an example job for GitHub Actions:
168 runs-on: ubuntu-latest
170 - uses: actions/checkout@v3
173 rustup toolchain install nightly --component miri
174 rustup override set nightly
176 - name: Test with Miri
180 The explicit `cargo miri setup` helps to keep the output of the actual test step
183 ### Testing for alignment issues
185 Miri can sometimes miss misaligned accesses since allocations can "happen to be"
186 aligned just right. You can use `-Zmiri-symbolic-alignment-check` to definitely
187 catch all such issues, but that flag will also cause false positives when code
188 does manual pointer arithmetic to account for alignment. Another alternative is
189 to call Miri with various values for `-Zmiri-seed`; that will alter the
190 randomness that is used to determine allocation base addresses. The following
191 snippet calls Miri in a loop with different values for the seed:
194 for seed in $({ echo obase=16; seq 255; } | bc); do
195 MIRIFLAGS=-Zmiri-seed=$seed cargo miri test || { echo "Last seed: $seed"; break; };
199 ### Supported targets
201 Miri does not support all targets supported by Rust. The good news, however, is
202 that no matter your host OS/platform, it is easy to run code for *any* target
205 The following targets are tested on CI and thus should always work (to the
206 degree documented below):
208 - The best-supported target is `x86_64-unknown-linux-gnu`. Miri releases are
209 blocked on things working with this target. Most other Linux targets should
210 also work well; we do run the test suite on `i686-unknown-linux-gnu` as a
211 32bit target and `mips64-unknown-linux-gnuabi64` as a big-endian target.
212 - `x86_64-apple-darwin` should work basically as well as Linux. We also test
213 `aarch64-apple-darwin`. However, we might ship Miri with a nightly even when
214 some features on these targets regress.
215 - `x86_64-pc-windows-msvc` works, but supports fewer features than the Linux and
216 Apple targets. For example, file system access and concurrency are not
217 supported on Windows. We also test `i686-pc-windows-msvc`, with the same
218 reduced feature set. We might ship Miri with a nightly even when some features
219 on these targets regress.
223 When using the above instructions, you may encounter a number of confusing compiler
226 #### "note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace"
228 You may see this when trying to get Miri to display a backtrace. By default, Miri
229 doesn't expose any environment to the program, so running
230 `RUST_BACKTRACE=1 cargo miri test` will not do what you expect.
232 To get a backtrace, you need to disable isolation
233 [using `-Zmiri-disable-isolation`][miri-flags]:
236 RUST_BACKTRACE=1 MIRIFLAGS="-Zmiri-disable-isolation" cargo miri test
239 #### "found possibly newer version of crate `std` which `<dependency>` depends on"
241 Your build directory may contain artifacts from an earlier build that have/have
242 not been built for Miri. Run `cargo clean` before switching from non-Miri to
243 Miri builds and vice-versa.
245 #### "found crate `std` compiled by an incompatible version of rustc"
247 You may be running `cargo miri` with a different compiler version than the one
248 used to build the custom libstd that Miri uses, and Miri failed to detect that.
249 Try deleting `~/.cache/miri`.
251 #### "no mir for `std::rt::lang_start_internal`"
253 This means the sysroot you are using was not compiled with Miri in mind. This
254 should never happen when you use `cargo miri` because that takes care of setting
255 up the sysroot. If you are using `miri` (the Miri driver) directly, see the
256 [contributors' guide](CONTRIBUTING.md) for how to use `./miri` to best do that.
259 ## Miri `-Z` flags and environment variables
260 [miri-flags]: #miri--z-flags-and-environment-variables
262 Miri adds its own set of `-Z` flags, which are usually set via the `MIRIFLAGS`
263 environment variable. We first document the most relevant and most commonly used flags:
265 * `-Zmiri-compare-exchange-weak-failure-rate=<rate>` changes the failure rate of
266 `compare_exchange_weak` operations. The default is `0.8` (so 4 out of 5 weak ops will fail).
267 You can change it to any value between `0.0` and `1.0`, where `1.0` means it
268 will always fail and `0.0` means it will never fail. Note than setting it to
269 `1.0` will likely cause hangs, since it means programs using
270 `compare_exchange_weak` cannot make progress.
271 * `-Zmiri-disable-isolation` disables host isolation. As a consequence,
272 the program has access to host resources such as environment variables, file
273 systems, and randomness.
274 * `-Zmiri-isolation-error=<action>` configures Miri's response to operations
275 requiring host access while isolation is enabled. `abort`, `hide`, `warn`,
276 and `warn-nobacktrace` are the supported actions. The default is to `abort`,
277 which halts the machine. Some (but not all) operations also support continuing
278 execution with a "permission denied" error being returned to the program.
279 `warn` prints a full backtrace when that happen; `warn-nobacktrace` is less
280 verbose. `hide` hides the warning entirely.
281 * `-Zmiri-env-exclude=<var>` keeps the `var` environment variable isolated from the host so that it
282 cannot be accessed by the program. Can be used multiple times to exclude several variables. The
283 `TERM` environment variable is excluded by default to [speed up the test
284 harness](https://github.com/rust-lang/miri/issues/1702). This has no effect unless
285 `-Zmiri-disable-isolation` is also set.
286 * `-Zmiri-env-forward=<var>` forwards the `var` environment variable to the interpreted program. Can
287 be used multiple times to forward several variables. This has no effect if
288 `-Zmiri-disable-isolation` is set.
289 * `-Zmiri-ignore-leaks` disables the memory leak checker, and also allows some
290 remaining threads to exist when the main thread exits.
291 * `-Zmiri-preemption-rate` configures the probability that at the end of a basic block, the active
292 thread will be preempted. The default is `0.01` (i.e., 1%). Setting this to `0` disables
294 * `-Zmiri-seed=<hex>` configures the seed of the RNG that Miri uses to resolve non-determinism. This
295 RNG is used to pick base addresses for allocations, to determine preemption and failure of
296 `compare_exchange_weak`, and to control store buffering for weak memory emulation. When isolation
297 is enabled (the default), this is also used to emulate system entropy. The default seed is 0. You
298 can increase test coverage by running Miri multiple times with different seeds. **NOTE**: This
299 entropy is not good enough for cryptographic use! Do not generate secret keys in Miri or perform
300 other kinds of cryptographic operations that rely on proper random numbers.
301 * `-Zmiri-strict-provenance` enables [strict
302 provenance](https://github.com/rust-lang/rust/issues/95228) checking in Miri. This means that
303 casting an integer to a pointer yields a result with 'invalid' provenance, i.e., with provenance
304 that cannot be used for any memory access. Also implies `-Zmiri-tag-raw-pointers`.
306 The remaining flags are for advanced use only, and more likely to change or be removed.
307 Some of these are **unsound**, which means they can lead
308 to Miri failing to detect cases of undefined behavior in a program.
310 * `-Zmiri-allow-uninit-numbers` disables the check to ensure that number types (integer and float
311 types) always hold initialized data. (They must still be initialized when any actual operation,
312 such as arithmetic, is performed.) Using this flag is **unsound**. This has no effect when
313 `-Zmiri-disable-validation` is present.
314 * `-Zmiri-allow-ptr-int-transmute` makes Miri more accepting of transmutation between pointers and
315 integers via `mem::transmute` or union/pointer type punning. This has two effects: it disables the
316 check against integers storing a pointer (i.e., data with provenance), thus allowing
317 pointer-to-integer transmutation, and it treats integer-to-pointer transmutation as equivalent to
318 a cast. Using this flag is **unsound**.
319 * `-Zmiri-disable-abi-check` disables checking [function ABI]. Using this flag
321 * `-Zmiri-disable-alignment-check` disables checking pointer alignment, so you
322 can focus on other failures, but it means Miri can miss bugs in your program.
323 Using this flag is **unsound**.
324 * `-Zmiri-disable-data-race-detector` disables checking for data races. Using
325 this flag is **unsound**. This implies `-Zmiri-disable-weak-memory-emulation`.
326 * `-Zmiri-disable-stacked-borrows` disables checking the experimental
327 [Stacked Borrows] aliasing rules. This can make Miri run faster, but it also
328 means no aliasing violations will be detected. Using this flag is **unsound**
329 (but the affected soundness rules are experimental).
330 * `-Zmiri-disable-validation` disables enforcing validity invariants, which are
331 enforced by default. This is mostly useful to focus on other failures (such
332 as out-of-bounds accesses) first. Setting this flag means Miri can miss bugs
333 in your program. However, this can also help to make Miri run faster. Using
334 this flag is **unsound**.
335 * `-Zmiri-disable-weak-memory-emulation` disables the emulation of some C++11 weak
337 * `-Zmiri-measureme=<name>` enables `measureme` profiling for the interpreted program.
338 This can be used to find which parts of your program are executing slowly under Miri.
339 The profile is written out to a file with the prefix `<name>`, and can be processed
340 using the tools in the repository https://github.com/rust-lang/measureme.
341 * `-Zmiri-mute-stdout-stderr` silently ignores all writes to stdout and stderr,
342 but reports to the program that it did actually write. This is useful when you
343 are not interested in the actual program's output, but only want to see Miri's
345 * `-Zmiri-panic-on-unsupported` will makes some forms of unsupported functionality,
346 such as FFI and unsupported syscalls, panic within the context of the emulated
347 application instead of raising an error within the context of Miri (and halting
348 execution). Note that code might not expect these operations to ever panic, so
349 this flag can lead to strange (mis)behavior.
350 * `-Zmiri-permissive-provenance` is **experimental**. This will make Miri do a
351 best-effort attempt to implement the semantics of
352 [`expose_addr`](https://doc.rust-lang.org/nightly/std/primitive.pointer.html#method.expose_addr)
354 [`ptr::from_exposed_addr`](https://doc.rust-lang.org/nightly/std/ptr/fn.from_exposed_addr.html)
355 for pointer-to-int and int-to-pointer casts, respectively. This will
356 necessarily miss some bugs as those semantics are not efficiently
357 implementable in a sanitizer, but it will only miss bugs that concerns
358 memory/pointers which is subject to these operations. Also note that this flag
359 is currently incompatible with Stacked Borrows, so you will have to also pass
360 `-Zmiri-disable-stacked-borrows` to use this.
361 * `-Zmiri-symbolic-alignment-check` makes the alignment check more strict. By
362 default, alignment is checked by casting the pointer to an integer, and making
363 sure that is a multiple of the alignment. This can lead to cases where a
364 program passes the alignment check by pure chance, because things "happened to
365 be" sufficiently aligned -- there is no UB in this execution but there would
366 be UB in others. To avoid such cases, the symbolic alignment check only takes
367 into account the requested alignment of the relevant allocation, and the
368 offset into that allocation. This avoids missing such bugs, but it also
369 incurs some false positives when the code does manual integer arithmetic to
370 ensure alignment. (The standard library `align_to` method works fine in both
371 modes; under symbolic alignment it only fills the middle slice when the
372 allocation guarantees sufficient alignment.)
373 * `-Zmiri-track-alloc-id=<id1>,<id2>,...` shows a backtrace when the given allocations are
374 being allocated or freed. This helps in debugging memory leaks and
375 use after free bugs. Specifying this argument multiple times does not overwrite the previous
376 values, instead it appends its values to the list. Listing an id multiple times has no effect.
377 * `-Zmiri-track-call-id=<id1>,<id2>,...` shows a backtrace when the given call ids are
378 assigned to a stack frame. This helps in debugging UB related to Stacked
379 Borrows "protectors". Specifying this argument multiple times does not overwrite the previous
380 values, instead it appends its values to the list. Listing an id multiple times has no effect.
381 * `-Zmiri-track-pointer-tag=<tag1>,<tag2>,...` shows a backtrace when a given pointer tag
382 is popped from a borrow stack (which is where the tag becomes invalid and any
383 future use of it will error). This helps you in finding out why UB is
384 happening and where in your code would be a good place to look for it.
385 Specifying this argument multiple times does not overwrite the previous
386 values, instead it appends its values to the list. Listing a tag multiple times has no effect.
387 * `-Zmiri-tag-raw-pointers` makes Stacked Borrows assign proper tags even for raw pointers. This can
388 make valid code using int-to-ptr casts fail to pass the checks, but also can help identify latent
389 aliasing issues in code that Miri accepts by default. You can recognize false positives by
390 `<untagged>` occurring in the message -- this indicates a pointer that was cast from an integer,
391 so Miri was unable to track this pointer. Note that it is not currently guaranteed that code that
392 works with `-Zmiri-tag-raw-pointers` also works without `-Zmiri-tag-raw-pointers`, but for the
393 vast majority of code, this will be the case.
395 [function ABI]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
397 Some native rustc `-Z` flags are also very relevant for Miri:
399 * `-Zmir-opt-level` controls how many MIR optimizations are performed. Miri
400 overrides the default to be `0`; be advised that using any higher level can
401 make Miri miss bugs in your program because they got optimized away.
402 * `-Zalways-encode-mir` makes rustc dump MIR even for completely monomorphic
403 functions. This is needed so that Miri can execute such functions, so Miri
404 sets this flag per default.
405 * `-Zmir-emit-retag` controls whether `Retag` statements are emitted. Miri
406 enables this per default because it is needed for [Stacked Borrows].
408 Moreover, Miri recognizes some environment variables:
410 * `MIRI_LOG`, `MIRI_BACKTRACE` control logging and backtrace printing during
411 Miri executions, also [see "Testing the Miri driver" in `CONTRIBUTING.md`][testing-miri].
412 * `MIRIFLAGS` (recognized by `cargo miri` and the test suite) defines extra
413 flags to be passed to Miri.
414 * `MIRI_LIB_SRC` defines the directory where Miri expects the sources of the
415 standard library that it will build and use for interpretation. This directory
416 must point to the `library` subdirectory of a `rust-lang/rust` repository
417 checkout. Note that changing files in that directory does not automatically
418 trigger a re-build of the standard library; you have to clear the Miri build
419 cache manually (on Linux, `rm -rf ~/.cache/miri`).
420 * `MIRI_SYSROOT` (recognized by `cargo miri` and the test suite) indicates the
421 sysroot to use. Only set this if you do not want to use the automatically
422 created sysroot. (The `miri` driver sysroot is controlled via the `--sysroot`
424 * `MIRI_TEST_TARGET` (recognized by the test suite) indicates which target
425 architecture to test against. `miri` and `cargo miri` accept the `--target`
426 flag for the same purpose.
427 * `MIRI_BLESS` (recognized by the test suite) overwrite all `stderr` and `stdout` files
428 instead of checking whether the output matches.
429 * `MIRI_SKIP_UI_CHECKS` (recognized by the test suite) don't check whether the
430 `stderr` or `stdout` files match the actual output. Useful for the rustc test suite
431 which has subtle differences that we don't care about.
433 The following environment variables are *internal* and must not be used by
434 anyone but Miri itself. They are used to communicate between different Miri
435 binaries, and as such worth documenting:
437 * `MIRI_BE_RUSTC` can be set to `host` or `target`. It tells the Miri driver to
438 actually not interpret the code but compile it like rustc would. With `target`, Miri sets
439 some compiler flags to prepare the code for interpretation; with `host`, this is not done.
440 This environment variable is useful to be sure that the compiled `rlib`s are compatible
442 * `MIRI_CALLED_FROM_XARGO` is set during the Miri-induced `xargo` sysroot build,
443 which will re-invoke `cargo-miri` as the `rustc` to use for this build.
444 * `MIRI_CALLED_FROM_RUSTDOC` when set to any value tells `cargo-miri` that it is
445 running as a child process of `rustdoc`, which invokes it twice for each doc-test
446 and requires special treatment, most notably a check-only build before interpretation.
447 This is set by `cargo-miri` itself when running as a `rustdoc`-wrapper.
448 * `MIRI_CWD` when set to any value tells the Miri driver to change to the given
449 directory after loading all the source files, but before commencing
450 interpretation. This is useful if the interpreted program wants a different
451 working directory at run-time than at build-time.
452 * `MIRI_LOCAL_CRATES` is set by `cargo-miri` to tell the Miri driver which
453 crates should be given special treatment in diagnostics, in addition to the
454 crate currently being compiled.
455 * `MIRI_VERBOSE` when set to any value tells the various `cargo-miri` phases to
456 perform verbose logging.
458 [testing-miri]: CONTRIBUTING.md#testing-the-miri-driver
460 ## Miri `extern` functions
462 Miri provides some `extern` functions that programs can import to access
463 Miri-specific functionality:
468 /// Miri-provided extern function to mark the block `ptr` points to as a "root"
469 /// for some static memory. This memory and everything reachable by it is not
470 /// considered leaking even if it still exists when the program terminates.
472 /// `ptr` has to point to the beginning of an allocated block.
473 fn miri_static_root(ptr: *const u8);
475 // Miri-provided extern function to get the amount of frames in the current backtrace.
476 // The `flags` argument must be `0`.
477 fn miri_backtrace_size(flags: u64) -> usize;
479 /// Miri-provided extern function to obtain a backtrace of the current call stack.
480 /// This writes a slice of pointers into `buf` - each pointer is an opaque value
481 /// that is only useful when passed to `miri_resolve_frame`.
482 /// `buf` must have `miri_backtrace_size(0) * pointer_size` bytes of space.
483 /// The `flags` argument must be `1`.
484 fn miri_get_backtrace(flags: u64, buf: *mut *mut ());
486 /// Miri-provided extern function to resolve a frame pointer obtained
487 /// from `miri_get_backtrace`. The `flags` argument must be `1`,
488 /// and `MiriFrame` should be declared as follows:
492 /// struct MiriFrame {
493 /// // The size of the name of the function being executed, encoded in UTF-8
495 /// // The size of filename of the function being executed, encoded in UTF-8
496 /// filename_len: usize,
497 /// // The line number currently being executed in `filename`, starting from '1'.
499 /// // The column number currently being executed in `filename`, starting from '1'.
501 /// // The function pointer to the function currently being executed.
502 /// // This can be compared against function pointers obtained by
503 /// // casting a function (e.g. `my_fn as *mut ()`)
508 /// The fields must be declared in exactly the same order as they appear in `MiriFrame` above.
509 /// This function can be called on any thread (not just the one which obtained `frame`).
510 fn miri_resolve_frame(frame: *mut (), flags: u64) -> MiriFrame;
512 /// Miri-provided extern function to get the name and filename of the frame provided by `miri_resolve_frame`.
513 /// `name_buf` and `filename_buf` should be allocated with the `name_len` and `filename_len` fields of `MiriFrame`.
514 /// The flags argument must be `0`.
515 fn miri_resolve_frame_names(ptr: *mut (), flags: u64, name_buf: *mut u8, filename_buf: *mut u8);
517 /// Miri-provided extern function to begin unwinding with the given payload.
519 /// This is internal and unstable and should not be used; we give it here
520 /// just to be complete.
521 fn miri_start_panic(payload: *mut u8) -> !;
525 ## Contributing and getting help
527 If you want to contribute to Miri, great! Please check out our
528 [contribution guide](CONTRIBUTING.md).
530 For help with running Miri, you can open an issue here on
531 GitHub or use the [Miri stream on the Rust Zulip][zulip].
533 [zulip]: https://rust-lang.zulipchat.com/#narrow/stream/269128-miri
537 This project began as part of an undergraduate research course in 2015 by
538 @solson at the [University of Saskatchewan][usask]. There are [slides] and a
539 [report] available from that project. In 2016, @oli-obk joined to prepare Miri
540 for eventually being used as const evaluator in the Rust compiler itself
541 (basically, for `const` and `static` stuff), replacing the old evaluator that
542 worked directly on the AST. In 2017, @RalfJung did an internship with Mozilla
543 and began developing Miri towards a tool for detecting undefined behavior, and
544 also using Miri as a way to explore the consequences of various possible
545 definitions for undefined behavior in Rust. @oli-obk's move of the Miri engine
546 into the compiler finally came to completion in early 2018. Meanwhile, later
547 that year, @RalfJung did a second internship, developing Miri further with
548 support for checking basic type invariants and verifying that references are
549 used according to their aliasing restrictions.
551 [usask]: https://www.usask.ca/
552 [slides]: https://solson.me/miri-slides.pdf
553 [report]: https://solson.me/miri-report.pdf
555 ## Bugs found by Miri
557 Miri has already found a number of bugs in the Rust standard library and beyond, which we collect here.
561 * [`Debug for vec_deque::Iter` accessing uninitialized memory](https://github.com/rust-lang/rust/issues/53566)
562 * [`Vec::into_iter` doing an unaligned ZST read](https://github.com/rust-lang/rust/pull/53804)
563 * [`From<&[T]> for Rc` creating a not sufficiently aligned reference](https://github.com/rust-lang/rust/issues/54908)
564 * [`BTreeMap` creating a shared reference pointing to a too small allocation](https://github.com/rust-lang/rust/issues/54957)
565 * [`Vec::append` creating a dangling reference](https://github.com/rust-lang/rust/pull/61082)
566 * [Futures turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/56319)
567 * [`str` turning a shared reference into a mutable one](https://github.com/rust-lang/rust/pull/58200)
568 * [`rand` performing unaligned reads](https://github.com/rust-random/rand/issues/779)
569 * [The Unix allocator calling `posix_memalign` in an invalid way](https://github.com/rust-lang/rust/issues/62251)
570 * [`getrandom` calling the `getrandom` syscall in an invalid way](https://github.com/rust-random/getrandom/pull/73)
571 * [`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
572 * [`beef` leaking memory](https://github.com/maciejhirsz/beef/issues/12)
573 * [`EbrCell` using uninitialized memory incorrectly](https://github.com/Firstyear/concread/commit/b15be53b6ec076acb295a5c0483cdb4bf9be838f#diff-6282b2fc8e98bd089a1f0c86f648157cR229)
574 * [TiKV performing an unaligned pointer access](https://github.com/tikv/tikv/issues/7613)
575 * [`servo_arc` creating a dangling shared reference](https://github.com/servo/servo/issues/26357)
576 * [TiKV constructing out-of-bounds pointers (and overlapping mutable references)](https://github.com/tikv/tikv/pull/7751)
577 * [`encoding_rs` doing out-of-bounds pointer arithmetic](https://github.com/hsivonen/encoding_rs/pull/53)
578 * [TiKV using `Vec::from_raw_parts` incorrectly](https://github.com/tikv/agatedb/pull/24)
579 * 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)
580 * [Insufficient alignment in `ThinVec`](https://github.com/Gankra/thin-vec/pull/27)
581 * [`crossbeam-epoch` calling `assume_init` on a partly-initialized `MaybeUninit`](https://github.com/crossbeam-rs/crossbeam/pull/779)
582 * [`integer-encoding` dereferencing a misaligned pointer](https://github.com/dermesser/integer-encoding-rs/pull/23)
583 * [`rkyv` constructing a `Box<[u8]>` from an overaligned allocation](https://github.com/rkyv/rkyv/commit/a9417193a34757e12e24263178be8b2eebb72456)
585 Violations of [Stacked Borrows] found that are likely bugs (but Stacked Borrows is currently just an experiment):
587 * [`VecDeque::drain` creating overlapping mutable references](https://github.com/rust-lang/rust/pull/56161)
588 * Various `BTreeMap` problems
589 * [`BTreeMap` iterators creating mutable references that overlap with shared references](https://github.com/rust-lang/rust/pull/58431)
590 * [`BTreeMap::iter_mut` creating overlapping mutable references](https://github.com/rust-lang/rust/issues/73915)
591 * [`BTreeMap` node insertion using raw pointers outside their valid memory area](https://github.com/rust-lang/rust/issues/78477)
592 * [`LinkedList` cursor insertion creating overlapping mutable references](https://github.com/rust-lang/rust/pull/60072)
593 * [`Vec::push` invalidating existing references into the vector](https://github.com/rust-lang/rust/issues/60847)
594 * [`align_to_mut` violating uniqueness of mutable references](https://github.com/rust-lang/rust/issues/68549)
595 * [`sized-chunks` creating aliasing mutable references](https://github.com/bodil/sized-chunks/issues/8)
596 * [`String::push_str` invalidating existing references into the string](https://github.com/rust-lang/rust/issues/70301)
597 * [`ryu` using raw pointers outside their valid memory area](https://github.com/dtolnay/ryu/issues/24)
598 * [ink! creating overlapping mutable references](https://github.com/rust-lang/miri/issues/1364)
599 * [TiKV creating overlapping mutable reference and raw pointer](https://github.com/tikv/tikv/pull/7709)
600 * [Windows `Env` iterator using a raw pointer outside its valid memory area](https://github.com/rust-lang/rust/pull/70479)
601 * [`VecDeque::iter_mut` creating overlapping mutable references](https://github.com/rust-lang/rust/issues/74029)
602 * [Various standard library aliasing issues involving raw pointers](https://github.com/rust-lang/rust/pull/78602)
603 * [`<[T]>::copy_within` using a loan after invalidating it](https://github.com/rust-lang/rust/pull/85610)
605 ## Scientific papers employing Miri
607 * [Stacked Borrows: An Aliasing Model for Rust](https://plv.mpi-sws.org/rustbelt/stacked-borrows/)
608 * [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)
609 * [SyRust: Automatic Testing of Rust Libraries with Semantic-Aware Program Synthesis](https://dl.acm.org/doi/10.1145/3453483.3454084)
613 Licensed under either of
615 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
616 http://www.apache.org/licenses/LICENSE-2.0)
617 * MIT license ([LICENSE-MIT](LICENSE-MIT) or
618 http://opensource.org/licenses/MIT)
624 Unless you explicitly state otherwise, any contribution intentionally submitted
625 for inclusion in the work by you shall be dual licensed as above, without any
626 additional terms or conditions.