Merge #879

879: epoch: Adjust MAX_OBJECTS r=taiki-e a=taiki-e

- Revert #552 to mitigate the risk of segmentation faults in buggy downstream implementations (see #869)
- Reduce MAX_OBJECTS on cfg(miri)

Co-authored-by: Taiki Endo <te316e89@gmail.com>

crossbeam-epoch/src/internal.rs

@@ -55,9 +55,10 @@ use crate::sync::list::{Entry, IsElement, IterError, List};
 use crate::sync::queue::Queue;
 
 /// Maximum number of objects a bag can contain.
-#[cfg(not(crossbeam_sanitize))]
-const MAX_OBJECTS: usize = 62;
-#[cfg(crossbeam_sanitize)]
+#[cfg(not(any(crossbeam_sanitize, miri)))]
+const MAX_OBJECTS: usize = 64;
+// Makes it more likely to trigger any potential data races.
+#[cfg(any(crossbeam_sanitize, miri))]
 const MAX_OBJECTS: usize = 4;
 
 /// A bag of deferred functions.
@@ -297,13 +298,14 @@ pub(crate) struct Local {
 
 // Make sure `Local` is less than or equal to 2048 bytes.
 // https://github.com/crossbeam-rs/crossbeam/issues/551
-#[cfg(not(crossbeam_sanitize))] // `crossbeam_sanitize` reduces the size of `Local`
+#[cfg(not(any(crossbeam_sanitize, miri)))] // `crossbeam_sanitize` and `miri` reduce the size of `Local`
 #[test]
 fn local_size() {
-    assert!(
-        core::mem::size_of::<Local>() <= 2048,
-        "An allocation of `Local` should be <= 2048 bytes."
-    );
+    // TODO: https://github.com/crossbeam-rs/crossbeam/issues/869
+    // assert!(
+    //     core::mem::size_of::<Local>() <= 2048,
+    //     "An allocation of `Local` should be <= 2048 bytes."
+    // );
 }
 
 impl Local {