Merge pull request #483 from apoelstra/2018-10-readme

improve README instructions for using `rustup` and for compiling separate crates

Author: RalfJung

.travis.yml

@@ -18,9 +18,8 @@ before_script:
   if [ "$TRAVIS_EVENT_TYPE" = cron ]; then
     RUST_TOOLCHAIN=nightly
   else
-    RUST_TOOLCHAIN=$(cat rust-toolchain)
+    RUST_TOOLCHAIN=$(cat rust-version)
   fi
-- rm rust-toolchain
 # install Rust
 - curl https://build.travis-ci.org/files/rustup-init.sh -sSf | sh -s -- -y --default-toolchain "$RUST_TOOLCHAIN"
 - export PATH=$HOME/.cargo/bin:$PATH

README.md

@@ -8,17 +8,19 @@ undergraduate research course at the [University of Saskatchewan][usask].
 ## Building Miri
 
 I recommend that you install [rustup][rustup] to obtain Rust.  Miri comes with a
-`rust-toolchain` file so rustup will automatically pick a suitable nightly
-version.  Then all you have to do is:
+`rust-version` file describing the latest supported nightly version of the Rust
+compiler toolchain. Then all you have to do is:
 
 ```sh
-cargo build
+cargo +nightly build
 ```
 
+with `+nightly` replaced with the appropriate nightly version of Rust.
+
 ## Running Miri
 
 ```sh
-cargo run tests/run-pass/vecs.rs # Or whatever test you like.
+cargo +nightly run tests/run-pass/vecs.rs # Or whatever test you like.
 ```
 
 ## Running Miri with full libstd
@@ -28,15 +30,15 @@ Miri hits a call to such a function, execution terminates. To fix this, it is
 possible to compile libstd with full MIR:
 
 ```sh
-rustup component add rust-src
-cargo install xargo
-xargo/build.sh
+rustup component add --toolchain nightly rust-src
+cargo +nightly install xargo
+rustup run nightly xargo/build.sh
 ```
 
 Now you can run Miri against the libstd compiled by xargo:
 
 ```sh
-MIRI_SYSROOT=~/.xargo/HOST cargo run tests/run-pass-fullmir/hashmap.rs
+MIRI_SYSROOT=~/.xargo/HOST cargo +nightly run tests/run-pass-fullmir/hashmap.rs
 ```
 
 Notice that you will have to re-run the last step of the preparations above when
@@ -47,13 +49,39 @@ You can also set `-Zmiri-start-fn` to make Miri start evaluation with the
 
 ## Running Miri on your own project('s test suite)
 
-Install Miri as a cargo subcommand with `cargo install --all-features`, and install
-a full libstd as described above.
+Install Miri as a cargo subcommand with `cargo install +nightly --all-features --path .`.
+
+Compile your project and its dependencies against a MIR-enabled libstd as described
+above:
+
+1. Run `cargo clean` to eliminate any cached dependencies that were built against
+the non-MIR `libstd`.
+2. To run all tests in your project through, Miri, use
+`MIRI_SYSROOT=~/.xargo/HOST cargo +nightly miri test`.
+3. If you have a binary project, you can run it through Miri using
+`MIRI_SYSROOT=~/.xargo/HOST cargo +nightly miri`.
+
+### Common Problems
+
+When using the above instructions, you may encounter a number of confusing compiler
+errors.
+
+#### "constant evaluation error: no mir for `<function>`"
+
+You may have forgotten to set `MIRI_SYSROOT` when calling `cargo miri`, and
+your program called into `std` or `core`. Be sure to set `MIRI_SYSROOT=~/.xargo/HOST`.
+
+#### "found possibly newer version of crate `std` which `<dependency>` depends on"
+
+Your build directory may contain artifacts from an earlier build that did/did not
+have `MIRI_SYSROOT` set. Run `cargo clean` before switching from non-Miri to Miri
+builds and vice-versa.
+
+#### "found crate `std` compiled by an incompatible version of rustc"
 
-Then, inside your own project, use `MIRI_SYSROOT=~/.xargo/HOST cargo +nightly
-miri` to run your project, if it is a bin project, or run
-`MIRI_SYSROOT=~/.xargo/HOST cargo +nightly miri test` to run all tests in your
-project through Miri.
+You may be running `cargo miri` with a different compiler version than the one
+used to build the MIR-enabled `std`. Be sure to consistently use the same toolchain,
+which should be the toolchain specified in the `rust-version` file.
 
 ## Miri `-Z` flags
 

appveyor.yml

@@ -16,7 +16,7 @@ branches:
 install:
     # install Rust
     - set PATH=C:\Program Files\Git\mingw64\bin;C:\msys64\mingw%MSYS2_BITS%\bin;%PATH%
-    - set /p RUST_TOOLCHAIN=<rust-toolchain
+    - set /p RUST_TOOLCHAIN=<rust-version
     - curl -sSf -o rustup-init.exe https://win.rustup.rs/
     - rustup-init.exe -y --default-host %TARGET% --default-toolchain %RUST_TOOLCHAIN%
     - set PATH=%USERPROFILE%\.cargo\bin;%PATH%