Auto merge of rust-lang#2241 - RalfJung:extern_static_in_const, r=RalfJung

fix ICE when const refers to extern static

Fixes rust-lang/miri#2234
Needs rust-lang#98099

Author: bors

rust-version

@@ -1 +1 @@
-cdcc53b7dc002ea4a7a28105010c5a1126ee31b7
+a09c668c965f735f4cd59e7158662b9daa0b71ba

src/machine.rs

@@ -618,7 +618,7 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'mir, 'tcx> {
         id: AllocId,
         alloc: Cow<'b, Allocation>,
         kind: Option<MemoryKind<Self::MemoryKind>>,
-    ) -> Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>> {
+    ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>> {
         if ecx.machine.tracked_alloc_ids.contains(&id) {
             register_diagnostic(NonHaltingDiagnostic::CreatedAlloc(id));
         }
@@ -653,15 +653,28 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'mir, 'tcx> {
                 data_race: race_alloc,
                 weak_memory: buffer_alloc,
             },
-            |ptr| Evaluator::tag_alloc_base_pointer(ecx, ptr),
-        );
-        Cow::Owned(alloc)
+            |ptr| ecx.global_base_pointer(ptr),
+        )?;
+        Ok(Cow::Owned(alloc))
     }
 
     fn tag_alloc_base_pointer(
         ecx: &MiriEvalContext<'mir, 'tcx>,
         ptr: Pointer<AllocId>,
     ) -> Pointer<Tag> {
+        if cfg!(debug_assertions) {
+            // The machine promises to never call us on thread-local or extern statics.
+            let alloc_id = ptr.provenance;
+            match ecx.tcx.get_global_alloc(alloc_id) {
+                Some(GlobalAlloc::Static(def_id)) if ecx.tcx.is_thread_local_static(def_id) => {
+                    panic!("tag_alloc_base_pointer called on thread-local static")
+                }
+                Some(GlobalAlloc::Static(def_id)) if ecx.tcx.is_foreign_item(def_id) => {
+                    panic!("tag_alloc_base_pointer called on extern static")
+                }
+                _ => {}
+            }
+        }
         let absolute_addr = intptrcast::GlobalStateInner::rel_ptr_to_addr(ecx, ptr);
         let sb_tag = if let Some(stacked_borrows) = &ecx.machine.stacked_borrows {
             stacked_borrows.borrow_mut().base_tag(ptr.provenance)

src/thread.rs

@@ -587,7 +587,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             // This allocation will be deallocated when the thread dies, so it is not in read-only memory.
             allocation.mutability = Mutability::Mut;
             // Create a fresh allocation with this content.
-            let new_alloc = this.allocate_raw_ptr(allocation, MiriMemoryKind::Tls.into());
+            let new_alloc = this.allocate_raw_ptr(allocation, MiriMemoryKind::Tls.into())?;
             this.machine.threads.set_thread_local_alloc(def_id, new_alloc);
             Ok(new_alloc)
         }

tests/fail/extern_static_in_const.rs

@@ -0,0 +1,11 @@
+//! Even referencing an unknown `extern static` already triggers an error.
+
+extern "C" {
+    static E: [u8; 0];
+}
+
+static X: &'static [u8; 0] = unsafe { &E };
+
+fn main() {
+    let _val = X; //~ ERROR is not supported by Miri
+}

tests/fail/extern_static_in_const.stderr

@@ -0,0 +1,14 @@
+error: unsupported operation: `extern` static `E` from crate `extern_static_in_const` is not supported by Miri
+  --> $DIR/extern_static_in_const.rs:LL:CC
+   |
+LL |     let _val = X;
+   |                ^ `extern` static `E` from crate `extern_static_in_const` is not supported by Miri
+   |
+   = 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: inside `main` at $DIR/extern_static_in_const.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to previous error
+