fixups

Author: nia-e

src/alloc/alloc_bytes.rs

@@ -119,6 +119,8 @@ impl AllocBytes for MiriAllocBytes {
         let slice = slice.into();
         let size = slice.len();
         let align = align.bytes();
+        // We need to clone here, since one copy goes into the alloc_fn and
+        // another is stored in the actual MiriAllocBytes
         let p_clone = params.clone();
         // SAFETY: `alloc_fn` will only be used with `size != 0`.
         let alloc_fn = |layout| unsafe {

src/alloc/isolated_alloc.rs

@@ -42,7 +42,6 @@ impl IsolatedAlloc {
         assert_ne!(page_size, 0);
 
         let page_layout = unsafe { Layout::from_size_align_unchecked(page_size, page_size) };
-        // We don't overwrite the bytes we hand out so make sure they're zeroed by default!
         let page_ptr = unsafe { alloc::alloc(page_layout) };
         // `page_infos` has to have one-eighth as many bits as a page has bytes
         // (or one-64th as many bytes)
@@ -140,7 +139,7 @@ impl IsolatedAlloc {
 
     /// Allocates in multiples of one page on the host system.
     ///
-    /// SAFETY: Same as `alloc_inner()`.
+    /// SAFETY: Same as `alloc()`.
     unsafe fn alloc_multi_page(&mut self, layout: Layout, zeroed: bool) -> *mut u8 {
         let ret =
             unsafe { if zeroed { alloc::alloc_zeroed(layout) } else { alloc::alloc(layout) } };

src/machine.rs

@@ -534,7 +534,7 @@ pub struct MiriMachine<'tcx> {
 
     /// The allocator used for the machine's `AllocBytes` in native-libs mode.
     #[cfg(target_os = "linux")]
-    pub(crate) allocator: Rc<RefCell<crate::alloc::isolated_alloc::IsolatedAlloc>>,
+    pub(crate) allocator: Option<Rc<RefCell<crate::alloc::isolated_alloc::IsolatedAlloc>>>,
 
     /// The allocation IDs to report when they are being allocated
     /// (helps for debugging memory leaks and use after free bugs).
@@ -642,8 +642,7 @@ impl<'tcx> MiriMachine<'tcx> {
             let path = Path::new(out).join(filename);
             measureme::Profiler::new(path).expect("Couldn't create `measureme` profiler")
         });
-        let seed = config.seed.unwrap_or(0);
-        let rng = StdRng::seed_from_u64(seed);
+        let rng = StdRng::seed_from_u64(config.seed.unwrap_or(0));
         let borrow_tracker = config.borrow_tracker.map(|bt| bt.instantiate_global_state(config));
         let data_race = if config.genmc_mode {
             // `genmc_ctx` persists across executions, so we don't create a new one here.
@@ -721,7 +720,9 @@ impl<'tcx> MiriMachine<'tcx> {
             extern_statics: FxHashMap::default(),
             rng: RefCell::new(rng),
             #[cfg(target_os = "linux")]
-            allocator: Rc::new(RefCell::new(crate::alloc::isolated_alloc::IsolatedAlloc::new())),
+            allocator: if config.native_lib.is_some() {
+                Some(Rc::new(RefCell::new(crate::alloc::isolated_alloc::IsolatedAlloc::new())))
+            } else { None },
             tracked_alloc_ids: config.tracked_alloc_ids.clone(),
             track_alloc_accesses: config.track_alloc_accesses,
             check_alignment: config.check_alignment,
@@ -1817,10 +1818,9 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
         use crate::alloc::MiriAllocParams;
 
         #[cfg(target_os = "linux")]
-        if self.native_lib.is_some() {
-            MiriAllocParams::Isolated(self.allocator.clone())
-        } else {
-            MiriAllocParams::Global
+        match &self.allocator {
+            Some(alloc) => MiriAllocParams::Isolated(alloc.clone()),
+            None => MiriAllocParams::Global,
         }
         #[cfg(not(target_os = "linux"))]
         MiriAllocParams::Global