Auto merge of #1301 - RalfJung:global-leaks, r=RalfJung

memory reachable through globals is not a leak

Blocked on https://github.com/rust-lang/rust/pull/70762
Fixes https://github.com/rust-lang/miri/issues/940

rust-version

@@ -1 +1 @@
-e6cef0445779724b469ab7b9a8d3c05d9e848ca8
+42abbd8878d3b67238f3611b0587c704ba94f39c

src/machine.rs

@@ -6,6 +6,7 @@ use std::cell::RefCell;
 use std::num::NonZeroU64;
 use std::rc::Rc;
 use std::time::Instant;
+use std::fmt;
 
 use log::trace;
 use rand::rngs::StdRng;
@@ -69,6 +70,31 @@ impl Into<MemoryKind<MiriMemoryKind>> for MiriMemoryKind {
     }
 }
 
+impl MayLeak for MiriMemoryKind {
+    #[inline(always)]
+    fn may_leak(self) -> bool {
+        use self::MiriMemoryKind::*;
+        match self {
+            Rust | C | WinHeap | Env => false,
+            Machine | Global => true,
+        }
+    }
+}
+
+impl fmt::Display for MiriMemoryKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        use self::MiriMemoryKind::*;
+        match self {
+            Rust => write!(f, "Rust heap"),
+            C => write!(f, "C heap"),
+            WinHeap => write!(f, "Windows heap"),
+            Machine => write!(f, "machine-managed memory"),
+            Env => write!(f, "environment variable"),
+            Global => write!(f, "global"),
+        }
+    }
+}
+
 /// Extra per-allocation data
 #[derive(Debug, Clone)]
 pub struct AllocExtra {
@@ -525,14 +551,3 @@ impl AllocationExtra<Tag> for AllocExtra {
         }
     }
 }
-
-impl MayLeak for MiriMemoryKind {
-    #[inline(always)]
-    fn may_leak(self) -> bool {
-        use self::MiriMemoryKind::*;
-        match self {
-            Rust | C | WinHeap | Env => false,
-            Machine | Global => true,
-        }
-    }
-}

tests/compile-fail/stack_free.rs

@@ -1,7 +1,7 @@
 // Validation/SB changes why we fail
 // compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows
 
-// error-pattern: deallocating `Stack` memory using `Machine(Rust)` deallocation operation
+// error-pattern: deallocating stack variable memory using Rust heap deallocation operation
 
 fn main() {
     let x = 42;

tests/run-pass/leak-in-static.rs

@@ -0,0 +1,8 @@
+static mut LEAKER: Option<Box<Vec<i32>>> = None;
+
+fn main() {
+    // Having memory "leaked" in globals is allowed.
+    unsafe {
+        LEAKER = Some(Box::new(vec![0; 42]));
+    }
+}

tests/run-pass/panic/catch_panic.rs

@@ -77,9 +77,6 @@ fn main() {
     test(None, |_old_val| { debug_assert!(false); loop {} });
     test(None, |_old_val| { unsafe { (1 as *const i32).read() }; loop {} }); // trigger debug-assertion in libstd
 
-    // Cleanup: reset to default hook.
-    drop(std::panic::take_hook());
-
     eprintln!("Success!"); // Make sure we get this in stderr
 }