Auto merge of #2314 - RalfJung:unsized, r=RalfJung

adjust for removed unsized_locals

The Miri side of rust-lang/rust#98831

Author: bors

rust-version

@@ -1 +1 @@
-7665c3543079ebc3710b676d0fd6951bedfd4b29
+8824d131619e58a38bde8bcf56401629b91a204a

src/machine.rs

@@ -169,7 +169,7 @@ impl Provenance for Tag {
                 write!(f, "{:?}", sb)?;
             }
             Tag::Wildcard => {
-                write!(f, "[Wildcard]")?;
+                write!(f, "[wildcard]")?;
             }
         }
 

src/operator.rs

@@ -35,11 +35,13 @@ impl<'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'mir, 'tcx> {
                     Immediate::Scalar(l) => (l.check_init()?.to_bits(size)?, 0),
                     Immediate::ScalarPair(l1, l2) =>
                         (l1.check_init()?.to_bits(size)?, l2.check_init()?.to_bits(size)?),
+                    Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
                 };
                 let right = match **right {
                     Immediate::Scalar(r) => (r.check_init()?.to_bits(size)?, 0),
                     Immediate::ScalarPair(r1, r2) =>
                         (r1.check_init()?.to_bits(size)?, r2.check_init()?.to_bits(size)?),
+                    Immediate::Uninit => throw_ub!(InvalidUninitBytes(None)),
                 };
                 let res = match bin_op {
                     Eq => left == right,

src/shims/intrinsics.rs

@@ -68,12 +68,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             "volatile_load" => {
                 let [place] = check_arg_count(args)?;
                 let place = this.deref_operand(place)?;
-                this.copy_op(&place.into(), dest)?;
+                this.copy_op(&place.into(), dest, /*allow_transmute*/ false)?;
             }
             "volatile_store" => {
                 let [place, dest] = check_arg_count(args)?;
                 let place = this.deref_operand(place)?;
-                this.copy_op(dest, &place.into())?;
+                this.copy_op(dest, &place.into(), /*allow_transmute*/ false)?;
             }
 
             "write_bytes" | "volatile_set_memory" => {

tests/fail/data_race/stack_pop_race.rs

@@ -0,0 +1,22 @@
+// compile-flags: -Zmiri-preemption-rate=0
+use std::thread;
+
+#[derive(Copy, Clone)]
+struct MakeSend(*const i32);
+unsafe impl Send for MakeSend {}
+
+fn main() { race(0); }
+
+// Using an argument for the ptr to point to, since those do not get StorageDead.
+fn race(local: i32) {
+    let ptr = MakeSend(&local as *const i32);
+    thread::spawn(move || {
+        let ptr = ptr;
+        let _val = unsafe { *ptr.0 };
+    });
+    // Make the other thread go first so that it does not UAF.
+    thread::yield_now();
+    // Deallocating the local (when `main` returns)
+    // races with the read in the other thread.
+    // Make sure the error points at this function's end, not just the call site.
+} //~ERROR Data race detected between Deallocate on thread `main` and Read on thread `<unnamed>`

tests/fail/data_race/stack_pop_race.stderr

@@ -0,0 +1,20 @@
+error: Undefined Behavior: Data race detected between Deallocate on thread `main` and Read on thread `<unnamed>` at ALLOC
+  --> $DIR/stack_pop_race.rs:LL:CC
+   |
+LL | }
+   |  ^ Data race detected between Deallocate on thread `main` and Read on thread `<unnamed>` at ALLOC
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: backtrace:
+   = note: inside `race` at $DIR/stack_pop_race.rs:LL:CC
+note: inside `main` at $DIR/stack_pop_race.rs:LL:CC
+  --> $DIR/stack_pop_race.rs:LL:CC
+   |
+LL | fn main() { race(0); }
+   |             ^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

tests/fail/unsized-local.rs

@@ -0,0 +1,23 @@
+#![feature(unsized_locals)]
+#![allow(incomplete_features)]
+
+fn main() {
+    pub trait Foo {
+        fn foo(self) -> String;
+    }
+
+    struct A;
+
+    impl Foo for A {
+        fn foo(self) -> String {
+            format!("hello")
+        }
+    }
+
+    let x = *(Box::new(A) as Box<dyn Foo>); //~ERROR unsized locals are not supported
+    assert_eq!(x.foo(), format!("hello"));
+
+    // I'm not sure whether we want this to work
+    let x = Box::new(A) as Box<dyn Foo>;
+    assert_eq!(x.foo(), format!("hello"));
+}

tests/fail/unsized-local.stderr

@@ -0,0 +1,14 @@
+error: unsupported operation: unsized locals are not supported
+  --> $DIR/unsized-local.rs:LL:CC
+   |
+LL |     let x = *(Box::new(A) as Box<dyn Foo>);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsized locals are not supported
+   |
+   = help: this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support
+   = note: backtrace:
+   = note: inside `main` at $DIR/unsized-local.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+

tests/pass/dyn-traits.rs

@@ -1,6 +1,3 @@
-#![feature(unsized_locals, unsized_fn_params)]
-#![allow(incomplete_features)]
-
 fn ref_box_dyn() {
     struct Struct(i32);
 
@@ -75,6 +72,9 @@ fn box_box_trait() {
     assert!(unsafe { DROPPED });
 }
 
+// Disabled for now: unsized locals are not supported,
+// their current MIR encoding is just not great.
+/*
 fn unsized_dyn() {
     pub trait Foo {
         fn foo(self) -> String;
@@ -95,7 +95,6 @@ fn unsized_dyn() {
     let x = Box::new(A) as Box<dyn Foo>;
     assert_eq!(x.foo(), format!("hello"));
 }
-
 fn unsized_dyn_autoderef() {
     pub trait Foo {
         fn foo(self) -> String;
@@ -140,12 +139,9 @@ fn unsized_dyn_autoderef() {
     let x = Box::new(|| "hello".to_owned()) as Box<dyn FnMut() -> String>;
     assert_eq!(&x.foo() as &str, "hello");
 }
+*/
 
 fn main() {
     ref_box_dyn();
     box_box_trait();
-
-    // "exotic" receivers
-    unsized_dyn();
-    unsized_dyn_autoderef();
 }

tests/pass/transmute_fat.rs

@@ -3,6 +3,7 @@
 
 fn main() {
     // If we are careful, we can exploit data layout...
+    // This is a tricky case since we are transmuting a ScalarPair type to a non-ScalarPair type.
     let raw = unsafe { std::mem::transmute::<&[u8], [*const u8; 2]>(&[42]) };
     let ptr: *const u8 = unsafe { std::mem::transmute_copy(&raw) };
     assert_eq!(unsafe { *ptr }, 42);