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, callingcopy_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: 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are properly supported (including some experimental emulation of weak memory effects, i.e., reads can return outdated values).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 currently 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.
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:
- 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. - To run all tests in your project through Miri, use
cargo miri test
. - 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
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 mips64-unknown-linux-gnuabi64
will run your test suite on a big-endian target, which is useful for testing
endian-sensitive code.
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.
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
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):
- The best-supported target is
x86_64-unknown-linux-gnu
. Miri releases are blocked on things working with this target. Most other Linux targets should also work well; we do run the test suite oni686-unknown-linux-gnu
as a 32bit target andmips64-unknown-linux-gnuabi64
as a big-endian target. x86_64-apple-darwin
should work basically as well as Linux. We also testaarch64-apple-darwin
. However, we might ship Miri with a nightly even when some features on these targets regress.x86_64-pc-windows-msvc
works, but supports fewer features than the Linux and Apple targets. For example, file system access and concurrency are not supported on Windows. We also testi686-pc-windows-msvc
, with the same reduced feature set. We might ship Miri with a nightly even when some features on these targets regress.
When using the above instructions, you may encounter a number of confusing compiler errors.
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
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.
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
.
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 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 ofcompare_exchange_weak
operations. The default is0.8
(so 4 out of 5 weak ops will fail). You can change it to any value between0.0
and1.0
, where1.0
means it will always fail and0.0
means it will never fail. Note than setting it to1.0
will likely cause hangs, since it means programs usingcompare_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-isolation-error=<action>
configures Miri's response to operations requiring host access while isolation is enabled.abort
,hide
,warn
, andwarn-nobacktrace
are the supported actions. The default is toabort
, 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-env-forward=<var>
forwards thevar
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-num-cpus
states the number of available CPUs to be reported by miri. By default, the number of available CPUs is1
. 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 andptr::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 is0.01
(i.e., 1%). Setting this to0
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 ofcompare_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 libraryalign_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.-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 Stacked Borrows aliasing rules. 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).-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>
enablesmeasureme
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 with the prefix<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
changes Stacked Borrows retagging to recurse into all fields. This means that references in fields of structs/enums/tuples/arrays/... are retagged, and in particular, they are protected when passed as function arguments. (The default is to recurse only in cases where rustc would actually emit anoalias
attribute.)-Zmiri-retag-fields=<all|none|scalar>
controls when Stacked Borrows retagging recurses into fields.all
means it always recurses (like-Zmiri-retag-fields
),none
means it never recurses,scalar
(the default) means it only recurses for types where we would also emitnoalias
annotations in the generated LLVM IR (types passed as indivudal scalars or pairs of scalars). Setting this tonone
is unsound.-Zmiri-tag-gc=<blocks>
configures how often the pointer tag garbage collector runs. The default is to search for and remove unreachable tags once every10000
basic blocks. Setting this to0
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-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.
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 be0
; 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 whetherRetag
statements are emitted. Miri enables this per default because it is needed for Stacked 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 any value, they are skipped. This is used for avoiding infinite recursion in./miri
and 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" inCONTRIBUTING.md
.MIRIFLAGS
(recognized bycargo 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 thelibrary
subdirectory of arust-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 bycargo miri
and the Miri driver) indicates the sysroot to use. When usingcargo 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 invokingcargo 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
andcargo miri
accept the--target
flag for the same purpose.MIRI_NO_STD
(recognized bycargo miri
and the test suite) makes sure that the target's sysroot is built without libstd. This allows testing and running no_std programs.MIRI_BLESS
(recognized by the test suite andcargo-miri-test/run-test.py
): overwrite allstderr
andstdout
files instead of checking whether the output matches.MIRI_SKIP_UI_CHECKS
(recognized by the test suite): don't check whether thestderr
orstdout
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 tohost
ortarget
. It tells the Miri driver to actually not interpret the code but compile it like rustc would. Withtarget
, Miri sets some compiler flags to prepare the code for interpretation; withhost
, this is not done. This environment variable is useful to be sure that the compiledrlib
s are compatible with Miri.MIRI_CALLED_FROM_SETUP
is set during the Miri sysroot build, which will re-invokecargo-miri
as therustc
to use for this build.MIRI_CALLED_FROM_RUSTDOC
when set to any value tellscargo-miri
that it is running as a child process ofrustdoc
, which invokes it twice for each doc-test and requires special treatment, most notably a check-only build before interpretation. This is set bycargo-miri
itself when running as arustdoc
-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 bycargo-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 variouscargo-miri
phases to perform verbose logging.MIRI_HOST_SYSROOT
is set by bootstrap to tellcargo-miri
which sysroot to use for host operations.
Miri provides some extern
functions that programs can import to access
Miri-specific functionality:
#[cfg(miri)]
extern "Rust" {
/// Miri-provided extern function to mark the block `ptr` points to as a "root"
/// for some static memory. This memory and everything reachable by it is not
/// considered leaking even if it still exists when the program terminates.
///
/// `ptr` has to point to the beginning of an allocated block.
fn miri_static_root(ptr: *const u8);
// Miri-provided extern function to get the amount of frames in the current backtrace.
// The `flags` argument must be `0`.
fn miri_backtrace_size(flags: u64) -> usize;
/// Miri-provided extern function to obtain a backtrace of the current call stack.
/// This writes a slice of pointers into `buf` - each pointer is an opaque value
/// that is only useful when passed to `miri_resolve_frame`.
/// `buf` must have `miri_backtrace_size(0) * pointer_size` bytes of space.
/// The `flags` argument must be `1`.
fn miri_get_backtrace(flags: u64, buf: *mut *mut ());
/// Miri-provided extern function to resolve a frame pointer obtained
/// from `miri_get_backtrace`. The `flags` argument must be `1`,
/// and `MiriFrame` should be declared as follows:
///
/// ```rust
/// #[repr(C)]
/// struct MiriFrame {
/// // The size of the name of the function being executed, encoded in UTF-8
/// name_len: usize,
/// // The size of filename of the function being executed, encoded in UTF-8
/// filename_len: usize,
/// // The line number currently being executed in `filename`, starting from '1'.
/// lineno: u32,
/// // The column number currently being executed in `filename`, starting from '1'.
/// colno: u32,
/// // The function pointer to the function currently being executed.
/// // This can be compared against function pointers obtained by
/// // casting a function (e.g. `my_fn as *mut ()`)
/// fn_ptr: *mut ()
/// }
/// ```
///
/// The fields must be declared in exactly the same order as they appear in `MiriFrame` above.
/// This function can be called on any thread (not just the one which obtained `frame`).
fn miri_resolve_frame(frame: *mut (), flags: u64) -> MiriFrame;
/// Miri-provided extern function to get the name and filename of the frame provided by `miri_resolve_frame`.
/// `name_buf` and `filename_buf` should be allocated with the `name_len` and `filename_len` fields of `MiriFrame`.
/// The flags argument must be `0`.
fn miri_resolve_frame_names(ptr: *mut (), flags: u64, name_buf: *mut u8, filename_buf: *mut u8);
/// Miri-provided extern function to begin unwinding with the given payload.
///
/// This is internal and unstable and should not be used; we give it here
/// just to be complete.
fn miri_start_panic(payload: *mut u8) -> !;
/// Miri-provided extern function to get the internal unique identifier for the allocation that a pointer
/// points to. If this pointer is invalid (not pointing to an allocation), interpretation will abort.
///
/// This is only useful as an input to `miri_print_borrow_stacks`, and it is a separate call because
/// getting a pointer to an allocation at runtime can change the borrow stacks in the allocation.
/// This function should be considered unstable. It exists only to support `miri_print_borrow_stacks` and so
/// inherits all of its instability.
fn miri_get_alloc_id(ptr: *const ()) -> u64;
/// Miri-provided extern function to print (from the interpreter, not the program) the contents of all
/// borrow stacks in an allocation. The leftmost tag is the bottom of the stack.
/// The format of what this emits is unstable and may change at any time. In particular, users should be
/// aware that Miri will periodically attempt to garbage collect the contents of all stacks. Callers of
/// this function may wish to pass `-Zmiri-tag-gc=0` to disable the GC.
///
/// This function is extremely unstable. At any time the format of its output may change, its signature may
/// change, or it may be removed entirely.
fn miri_print_borrow_stacks(alloc_id: u64);
/// Miri-provided extern function to print (from the interpreter, not the
/// program) the contents of a section of program memory, as bytes. Bytes
/// written using this function will emerge from the interpreter's stdout.
fn miri_write_to_stdout(bytes: &[u8]);
/// Miri-provided extern function to print (from the interpreter, not the
/// program) the contents of a section of program memory, as bytes. Bytes
/// written using this function will emerge from the interpreter's stderr.
fn miri_write_to_stderr(bytes: &[u8]);
/// Miri-provided extern function to allocate memory from the interpreter.
///
/// This is useful when no fundamental way of allocating memory is
/// available, e.g. when using `no_std` + `alloc`.
fn miri_alloc(size: usize, align: usize) -> *mut u8;
/// Miri-provided extern function to deallocate memory.
fn miri_dealloc(ptr: *mut u8, size: usize, align: usize);
/// Convert a path from the host Miri runs on to the target Miri interprets.
/// Performs conversion of path separators as needed.
///
/// Usually Miri performs this kind of conversion automatically. However, manual conversion
/// might be necessary when reading an environment variable that was set on the host
/// (such as TMPDIR) and using it as a target path.
///
/// Only works with isolation disabled.
///
/// `in` must point to a null-terminated string, and will be read as the input host path.
/// `out` must point to at least `out_size` many bytes, and the result will be stored there
/// with a null terminator.
/// Returns 0 if the `out` buffer was large enough, and the required size otherwise.
fn miri_host_to_target_path(path: *const i8, out: *mut i8, out_size: usize) -> usize;
}
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.
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.
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 memoryVec::into_iter
doing an unaligned ZST readFrom<&[T]> for Rc
creating a not sufficiently aligned referenceBTreeMap
creating a shared reference pointing to a too small allocationVec::append
creating a dangling reference- Futures turning a shared reference into a mutable one
str
turning a shared reference into a mutable onerand
performing unaligned reads- The Unix allocator calling
posix_memalign
in an invalid way getrandom
calling thegetrandom
syscall in an invalid wayVec
andBTreeMap
leaking memory under some (panicky) conditionsbeef
leaking memoryEbrCell
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
andBox::from_raw_in
- Insufficient alignment in
ThinVec
crossbeam-epoch
callingassume_init
on a partly-initializedMaybeUninit
integer-encoding
dereferencing a misaligned pointerrkyv
constructing aBox<[u8]>
from an overaligned allocation- Data race in
thread::scope
regex
incorrectly handling unalignedVec<u8>
buffers- Incorrect use of
compare_exchange_weak
inonce_cell
- Dropping with unaligned pointers in
vec::IntoIter
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 LinkedList
cursor insertion creating overlapping mutable referencesVec::push
invalidating existing references into the vectoralign_to_mut
violating uniqueness of mutable referencessized-chunks
creating aliasing mutable referencesString::push_str
invalidating existing references into the stringryu
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
- 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
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.
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.