all memory behind a constant must be immutable
diff --git a/src/librustc_mir/interpret/intern.rs b/src/librustc_mir/interpret/intern.rs
index e05b314..6333fce 100644
--- a/src/librustc_mir/interpret/intern.rs
+++ b/src/librustc_mir/interpret/intern.rs
@@ -304,9 +304,14 @@
let mut todo: Vec<_> = leftover_relocations.iter().cloned().collect();
while let Some(alloc_id) = todo.pop() {
- if let Some((_, alloc)) = ecx.memory_mut().alloc_map.remove(&alloc_id) {
+ if let Some((_, mut alloc)) = ecx.memory_mut().alloc_map.remove(&alloc_id) {
// We can't call the `intern_shallow` method here, as its logic is tailored to safe
// references. So we hand-roll the interning logic here again.
+ if base_intern_mode != InternMode::Static {
+ // If it's not a static, it *must* be immutable.
+ // We cannot have mutable memory inside a constant.
+ alloc.mutability = Mutability::Immutable;
+ }
let alloc = tcx.intern_const_alloc(alloc);
tcx.alloc_map.lock().set_alloc_id_memory(alloc_id, alloc);
for &(_, ((), reloc)) in alloc.relocations().iter() {
diff --git a/src/test/ui/consts/miri_unleashed/mutable_const.rs b/src/test/ui/consts/miri_unleashed/mutable_const.rs
new file mode 100644
index 0000000..b476e04
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/mutable_const.rs
@@ -0,0 +1,20 @@
+// compile-flags: -Zunleash-the-miri-inside-of-you
+
+#![feature(const_raw_ptr_deref)]
+#![deny(const_err)]
+
+use std::cell::UnsafeCell;
+
+// make sure we do not just intern this as mutable
+const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
+
+const MUTATING_BEHIND_RAW: () = {
+ // Test that `MUTABLE_BEHIND_RAW` is actually immutable, by doing this at const time.
+ unsafe {
+ *MUTABLE_BEHIND_RAW = 99 //~ WARN skipping const checks
+ //~^ ERROR any use of this value will cause an error
+ //~^^ tried to modify constant memory
+ }
+};
+
+fn main() {}
diff --git a/src/test/ui/consts/miri_unleashed/mutable_const.stderr b/src/test/ui/consts/miri_unleashed/mutable_const.stderr
new file mode 100644
index 0000000..507d4823
--- /dev/null
+++ b/src/test/ui/consts/miri_unleashed/mutable_const.stderr
@@ -0,0 +1,27 @@
+warning: skipping const checks
+ --> $DIR/mutable_const.rs:14:9
+ |
+LL | *MUTABLE_BEHIND_RAW = 99
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: any use of this value will cause an error
+ --> $DIR/mutable_const.rs:14:9
+ |
+LL | / const MUTATING_BEHIND_RAW: () = {
+LL | | // Test that `MUTABLE_BEHIND_RAW` is actually immutable, by doing this at const time.
+LL | | unsafe {
+LL | | *MUTABLE_BEHIND_RAW = 99
+ | | ^^^^^^^^^^^^^^^^^^^^^^^^ tried to modify constant memory
+... |
+LL | | }
+LL | | };
+ | |__-
+ |
+note: lint level defined here
+ --> $DIR/mutable_const.rs:4:9
+ |
+LL | #![deny(const_err)]
+ | ^^^^^^^^^
+
+error: aborting due to previous error
+
