1 # Miri [[slides](https://solson.me/miri-slides.pdf)] [[report](https://solson.me/miri-report.pdf)] [![Build Status](https://travis-ci.org/solson/miri.svg?branch=master)](https://travis-ci.org/solson/miri) [![Windows build status](https://ci.appveyor.com/api/projects/status/github/solson/miri?svg=true)](https://ci.appveyor.com/project/solson63299/miri)
4 An experimental interpreter for [Rust][rust]'s [mid-level intermediate
5 representation][mir] (MIR). This project began as part of my work for the
6 undergraduate research course at the [University of Saskatchewan][usask].
10 We recommend that you install [rustup][rustup] to obtain Rust. Then all you have
17 This uses the very latest Rust version. If you experience any problem, refer to
18 the `rust-version` file which contains a particular Rust nightly version that
19 has been tested against the version of miri you are using. Make sure to use
20 that particular `nightly-YYYY-MM-DD` whenever the instructions just say
23 To avoid repeating the nightly version all the time, you can use
24 `rustup override set nightly` (or `rustup override set nightly-YYYY-MM-DD`),
25 which means `nightly` Rust will automatically be used whenever you are working
31 cargo +nightly run tests/run-pass/vecs.rs # Or whatever test you like.
34 ## Running Miri with full libstd
36 Per default libstd does not contain the MIR of non-polymorphic functions. When
37 Miri hits a call to such a function, execution terminates. To fix this, it is
38 possible to compile libstd with full MIR:
41 rustup component add --toolchain nightly rust-src
42 cargo +nightly install xargo
43 rustup run nightly xargo/build.sh
46 Now you can run Miri against the libstd compiled by xargo:
49 MIRI_SYSROOT=~/.xargo/HOST cargo +nightly run tests/run-pass-fullmir/hashmap.rs
52 Notice that you will have to re-run the last step of the preparations above
53 (`xargo/build.sh`) when your toolchain changes (e.g., when you update the
56 ## Running Miri on your own project('s test suite)
58 Install Miri as a cargo subcommand with `cargo install +nightly --all-features
59 --path .`. Be aware that if you used `rustup override set` to fix a particular
60 Rust version for the miri directory, that will *not* apply to your own project
61 directory! You have to use a consistent Rust version for building miri and your
62 project for this to work, so remember to either always specify the nightly
63 version manually, overriding it in your project directory as well, or use
64 `rustup default nightly` (or `rustup default nightly-YYYY-MM-DD`) to globally
65 make `nightly` the default toolchain.
67 We assume that you have prepared a MIR-enabled libstd as described above. Now
68 compile your project and its dependencies against that libstd:
70 1. Run `cargo clean` to eliminate any cached dependencies that were built against
72 2. To run all tests in your project through, Miri, use
73 `MIRI_SYSROOT=~/.xargo/HOST cargo +nightly miri test`. **NOTE**: This is
74 currently broken, see the discussion in
75 [#479](https://github.com/solson/miri/issues/479).
76 3. If you have a binary project, you can run it through Miri using
77 `MIRI_SYSROOT=~/.xargo/HOST cargo +nightly miri`.
81 When using the above instructions, you may encounter a number of confusing compiler
84 #### "constant evaluation error: no mir for `<function>`"
86 You may have forgotten to set `MIRI_SYSROOT` when calling `cargo miri`, and
87 your program called into `std` or `core`. Be sure to set `MIRI_SYSROOT=~/.xargo/HOST`.
89 #### "found possibly newer version of crate `std` which `<dependency>` depends on"
91 Your build directory may contain artifacts from an earlier build that did/did not
92 have `MIRI_SYSROOT` set. Run `cargo clean` before switching from non-Miri to Miri
93 builds and vice-versa.
95 #### "found crate `std` compiled by an incompatible version of rustc"
97 You may be running `cargo miri` with a different compiler version than the one
98 used to build the MIR-enabled `std`. Be sure to consistently use the same toolchain,
99 which should be the toolchain specified in the `rust-version` file.
103 Several `-Z` flags are relevant for miri:
105 * `-Zmir-opt-level` controls how many MIR optimizations are performed. miri
106 overrides the default to be `0`; be advised that using any higher level can
107 make miri miss bugs in your program because they got optimized away.
108 * `-Zalways-encode-mir` makes rustc dump MIR even for completely monomorphic
109 functions. This is needed so that miri can execute such functions, so miri
110 sets this flag per default.
111 * `-Zmiri-disable-validation` is a custom `-Z` flag added by miri. It disables
112 enforcing the validity invariant, which is enforced by default. This is
113 mostly useful for debugging; it means miri will miss bugs in your program.
115 ## Development and Debugging
117 Since the heart of Miri (the main interpreter engine) lives in rustc, working on
118 Miri will often require using a locally built rustc. This includes getting a
119 trace of the execution, as distributed rustc has `debug!` and `trace!` disabled.
121 The first-time setup for a local rustc looks as follows:
123 git clone https://github.com/rust-lang/rust/ rustc
125 cp config.toml.example config.toml
126 # Now edit `config.toml` and set `debug-assertions = true` and `test-miri = true`.
127 # The latter is important to build libstd with the right flags for miri.
128 ./x.py build src/rustc
129 # You may have to change the architecture in the next command
130 rustup toolchain link custom build/x86_64-unknown-linux-gnu/stage2
131 # Now cd to your Miri directory
132 rustup override set custom
134 The `build` step can take 30 minutes and more.
136 Now you can `cargo build` Miri, and you can `cargo test --release` it. `cargo
137 test --release FILTER` only runs those tests that contain `FILTER` in their
138 filename (including the base directory, e.g. `cargo test --release fail` will
139 run all compile-fail tests). We recommend using `--release` to make test
140 running take less time.
142 Notice that the "fullmir" tests only run if you have `MIRI_SYSROOT` set, the
143 test runner does not realized that your libstd comes with full MIR. The
144 following will set it correctly:
146 MIRI_SYSROOT=$(rustc --print sysroot) cargo test --release
149 Moreover, you can now run Miri with a trace of all execution steps:
151 MIRI_LOG=debug cargo run tests/run-pass/vecs.rs
154 Setting `MIRI_LOG` like this will configure logging for miri itself as well as
155 the `rustc::mir::interpret` and `rustc_mir::interpret` modules in rustc. You
156 can also do more targeted configuration, e.g. to debug the stacked borrows
159 MIRI_LOG=rustc_mir::interpret=debug,miri::stacked_borrows cargo run tests/run-pass/vecs.rs
162 In addition, you can set `MIRI_BACKTRACE=1` to get a backtrace of where an
163 evaluation error was originally created.
165 If you changed something in rustc and want to re-build, run
167 ./x.py --keep-stage 0 build src/rustc
169 This avoids rebuilding the entire stage 0, which can save a lot of time.
171 ## Contributing and getting help
173 Check out the issues on this GitHub repository for some ideas. There's lots that
174 needs to be done that I haven't documented in the issues yet, however. For more
175 ideas or help with running or hacking on Miri, you can contact me (`scott`) on
176 Mozilla IRC in any of the Rust IRC channels (`#rust`, `#rust-offtopic`, etc).
180 Licensed under either of
181 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
182 http://www.apache.org/licenses/LICENSE-2.0)
183 * MIT license ([LICENSE-MIT](LICENSE-MIT) or
184 http://opensource.org/licenses/MIT) at your option.
188 Unless you explicitly state otherwise, any contribution intentionally submitted
189 for inclusion in the work by you shall be dual licensed as above, without any
190 additional terms or conditions.
192 [rust]: https://www.rust-lang.org/
193 [mir]: https://github.com/rust-lang/rfcs/blob/master/text/1211-mir.md
194 [usask]: https://www.usask.ca/
195 [rustup]: https://www.rustup.rs