Fix warnings with the stable Rust toolchain (#1099)

As getting a ref `&` of `static mut` variables will become a compilation
error in the Rust 2024 Edition, we use `unsafe { &*addr_of!(VM_LAYOUT)
}` to work around it. See: #1098

Changed the `static mut` in mock_test_doc_avoid_resolving_allocator.rs
to an ordinary local variable.

Initialize the thread-local variable `WORKER_ORDINAL` with a `const`
block. It avoids lazy initialization. We also bumped the `rust-version`
field in Cargo.toml to 1.71.1 because the semantics of the `const` block
in the `thread_local!` macro was undocumented in 1.70.0.

Cargo.toml

@@ -10,7 +10,7 @@ repository = "https://github.com/mmtk/mmtk-core"
 readme = "README.md"
 categories = ["memory-management"]
 keywords = ["gc", "garbage", "collection", "garbage-collection", "allocation"]
-rust-version = "1.70.0"
+rust-version = "1.71.1"
 build = "build.rs"
 
 [lib]

rust-toolchain

@@ -1 +1 @@
-1.71.1
+1.77.0

src/policy/lockfreeimmortalspace.rs

@@ -198,7 +198,9 @@ impl<VM: VMBinding> LockFreeImmortalSpace<VM> {
         // Create a VM request of fixed size
         let vmrequest = VMRequest::fixed_size(aligned_total_bytes);
         // Reserve the space
-        let VMRequest::Extent{ extent, top } = vmrequest else { unreachable!() };
+        let VMRequest::Extent { extent, top } = vmrequest else {
+            unreachable!()
+        };
         let start = args.heap.reserve(extent, top);
 
         let space = Self {

src/scheduler/worker.rs

@@ -19,7 +19,7 @@ pub type ThreadId = usize;
 
 thread_local! {
     /// Current worker's ordinal
-    static WORKER_ORDINAL: Atomic<ThreadId> = Atomic::new(ThreadId::MAX);
+    static WORKER_ORDINAL: Atomic<ThreadId> = const { Atomic::new(ThreadId::MAX) };
 }
 
 /// Get current worker ordinal. Return `None` if the current thread is not a worker.

src/util/heap/layout/vm_layout.rs

@@ -1,5 +1,6 @@
 //! The module defines virutal memory layout parameters.
 
+use std::ptr::addr_of;
 use std::sync::atomic::AtomicBool;
 
 use atomic::Ordering;
@@ -192,5 +193,5 @@ pub fn vm_layout() -> &'static VMLayout {
     if cfg!(debug_assertions) {
         VM_LAYOUT_FETCHED.store(true, Ordering::SeqCst);
     }
-    unsafe { &VM_LAYOUT }
+    unsafe { &*addr_of!(VM_LAYOUT) }
 }

src/vm/tests/mock_tests/mock_test_doc_avoid_resolving_allocator.rs

@@ -18,25 +18,22 @@ pub fn acquire_typed_allocator() {
         || {
             let fixture = MMTKFixture::create();
             let tls_opaque_pointer = VMMutatorThread(VMThread(OpaquePointer::UNINITIALIZED));
-            static mut DEFAULT_ALLOCATOR_OFFSET: usize = 0;
 
             // ANCHOR: avoid_resolving_allocator
             // At boot time
             let selector = memory_manager::get_allocator_mapping(
                 fixture.get_mmtk(),
                 AllocationSemantics::Default,
             );
-            unsafe {
-                DEFAULT_ALLOCATOR_OFFSET =
-                    crate::plan::Mutator::<MockVM>::get_allocator_base_offset(selector);
-            }
+            let default_allocator_offset =
+                crate::plan::Mutator::<MockVM>::get_allocator_base_offset(selector);
             let mutator = memory_manager::bind_mutator(fixture.get_mmtk(), tls_opaque_pointer);
 
             // At run time: allocate with the default semantics without resolving allocator
             let default_allocator: &mut BumpAllocator<MockVM> = {
                 let mutator_addr = Address::from_ref(&*mutator);
                 unsafe {
-                    (mutator_addr + DEFAULT_ALLOCATOR_OFFSET).as_mut_ref::<BumpAllocator<MockVM>>()
+                    (mutator_addr + default_allocator_offset).as_mut_ref::<BumpAllocator<MockVM>>()
                 }
             };
             let addr = default_allocator.alloc(8, 8, 0);