Merge remote-tracking branch 'origin/master' into rustup

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

@@ -7,18 +7,28 @@ 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:
+I recommend that you install [rustup][rustup] to obtain Rust. Then all you have
+to do is:
 
 ```sh
-cargo build
+cargo +nightly build
 ```
 
+This uses the very latest Rust version.  If you experience any problem, refer to
+the `rust-version` file which contains a particular Rust nightly version that
+has been tested against the version of miri you are using.  Make sure to use
+that particular `nightly-YYYY-MM-DD` whenever the instructions just say
+`nightly`.
+
+To avoid repeating the nightly version all the time, you can use
+`rustup override set nightly` (or `rustup override set nightly-YYYY-MM-DD`),
+which means `nightly` Rust will automatically be used whenever you are working
+in this directory.
+
 ## 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
@@ -28,40 +38,77 @@ 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
-your toolchain changes (e.g., when you update the nightly).
-
-You can also set `-Zmiri-start-fn` to make Miri start evaluation with the
-`start_fn` lang item, instead of starting at the `main` function.
+Notice that you will have to re-run the last step of the preparations above
+(`xargo/build.sh`) when your toolchain changes (e.g., when you update the
+nightly).
 
 ## 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 .`.  Be aware that if you used `rustup override set` to fix a particular
+Rust version for the miri directory, that will *not* apply to your own project
+directory!  You have to use a consistent Rust version for building miri and your
+project for this to work, so remember to either always specify the nightly
+version manually, overriding it in your project directory as well, or use
+`rustup default nightly` (or `rustup default nightly-YYYY-MM-DD`) to globally
+make `nightly` the default toolchain.
 
-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.
+We assume that you have prepared a MIR-enabled libstd as described above.  Now
+compile your project and its dependencies against that libstd:
 
-## Miri `-Z` flags
+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>`"
 
-Miri adds some extra `-Z` flags to control its behavior:
+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"
+
+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
 
-* `-Zmiri-start-fn`: This makes interpretation start with `lang_start` (defined
-  in libstd) instead of starting with `main`.  Requires full MIR!
-* `-Zmiri-disable-validation` disables enforcing the validity invariant.
+Several `-Z` flags are relevant for miri:
+
+* `-Zmir-opt-level` controls how many MIR optimizations are performed.  miri
+  overrides the default to be `0`; 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.
+* `-Zmiri-disable-validation` is a custom `-Z` flag added by miri.  It disables
+  enforcing the validity invariant, which is enforced by default.  This is
+  mostly useful for debugging; it means miri will miss bugs in your program.
 
 ## Development and Debugging
 

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%

rust-toolchain renamed to rust-version

@@ -132,7 +132,7 @@ impl<'a, 'mir, 'tcx: 'mir + 'a> EvalContextExt<'tcx, 'mir> for super::MiriEvalCo
 
             "free" => {
                 let ptr = self.read_scalar(args[0])?.not_undef()?.erase_tag(); // raw ptr operation, no tag
-                if !ptr.is_null() {
+                if !ptr.is_null_ptr(&self) {
                     self.memory_mut().deallocate(
                         ptr.to_ptr()?.with_default_tag(),
                         None,
@@ -355,7 +355,7 @@ impl<'a, 'mir, 'tcx: 'mir + 'a> EvalContextExt<'tcx, 'mir> for super::MiriEvalCo
                 let mut success = None;
                 {
                     let name_ptr = self.read_scalar(args[0])?.not_undef()?.erase_tag(); // raw ptr operation
-                    if !name_ptr.is_null() {
+                    if !name_ptr.is_null_ptr(&self) {
                         let name = self.memory().read_c_str(name_ptr.to_ptr()?
                             .with_default_tag())?.to_owned();
                         if !name.is_empty() && !name.contains(&b'=') {
@@ -379,7 +379,7 @@ impl<'a, 'mir, 'tcx: 'mir + 'a> EvalContextExt<'tcx, 'mir> for super::MiriEvalCo
                     let name_ptr = self.read_scalar(args[0])?.not_undef()?.erase_tag(); // raw ptr operation
                     let value_ptr = self.read_scalar(args[1])?.to_ptr()?.erase_tag(); // raw ptr operation
                     let value = self.memory().read_c_str(value_ptr.with_default_tag())?;
-                    if !name_ptr.is_null() {
+                    if !name_ptr.is_null_ptr(&self) {
                         let name = self.memory().read_c_str(name_ptr.to_ptr()?.with_default_tag())?;
                         if !name.is_empty() && !name.contains(&b'=') {
                             new = Some((name.to_owned(), value.to_owned()));

src/fn_call.rs

@@ -231,7 +231,7 @@ impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, '
                 let a = self.read_value(args[0])?;
                 let b = self.read_value(args[1])?;
                 // check x % y != 0
-                if !self.binary_op_val(mir::BinOp::Rem, a, b)?.0.is_null() {
+                if self.binary_op_val(mir::BinOp::Rem, a, b)?.0.to_bytes()? != 0 {
                     return err!(ValidationFailure(format!("exact_div: {:?} cannot be divided by {:?}", a, b)));
                 }
                 self.binop_ignore_overflow(mir::BinOp::Div, a, b, dest)?;

src/intrinsic.rs

@@ -121,7 +121,7 @@ impl<'tcx> TlsData<'tcx> {
         for (&key, &mut TlsEntry { ref mut data, dtor }) in
             thread_local.range_mut((start, Unbounded))
         {
-            if !data.is_null() {
+            if !data.is_null_ptr(cx) {
                 if let Some(dtor) = dtor {
                     let ret = Some((dtor, *data, key));
                     *data = Scalar::ptr_null(cx);