Change __rust_no_alloc_shim_is_unstable to be a function

Author: dpaoliello

src/shims/extern_static.rs

@@ -45,10 +45,6 @@ impl<'tcx> MiriMachine<'tcx> {
 
     /// Sets up the "extern statics" for this machine.
     pub fn init_extern_statics(ecx: &mut MiriInterpCx<'tcx>) -> InterpResult<'tcx> {
-        // "__rust_no_alloc_shim_is_unstable"
-        let val = ImmTy::from_int(0, ecx.machine.layouts.u8); // always 0, value does not matter
-        Self::alloc_extern_static(ecx, "__rust_no_alloc_shim_is_unstable", val)?;
-
         // "__rust_alloc_error_handler_should_panic"
         let val = ecx.tcx.sess.opts.unstable_opts.oom.should_panic();
         let val = ImmTy::from_int(val, ecx.machine.layouts.u8);

src/shims/foreign_items.rs

@@ -611,6 +611,10 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     this.write_pointer(new_ptr, dest)
                 });
             }
+            name if name == this.mangle_internal_symbol("__rust_no_alloc_shim_is_unstable_v2") => {
+                // This is a no-op shim that only exists to prevent making the allocator shims instantly stable.
+                let [] = this.check_shim(abi, CanonAbi::Rust, link_name, args)?;
+            }
 
             // C memory handling functions
             "memcmp" => {

tests/pass/alloc-access-tracking.rs

@@ -1,7 +1,7 @@
 #![no_std]
 #![no_main]
-//@compile-flags: -Zmiri-track-alloc-id=20 -Zmiri-track-alloc-accesses -Cpanic=abort
-//@normalize-stderr-test: "id 20" -> "id $$ALLOC"
+//@compile-flags: -Zmiri-track-alloc-id=19 -Zmiri-track-alloc-accesses -Cpanic=abort
+//@normalize-stderr-test: "id 19" -> "id $$ALLOC"
 //@only-target: linux # alloc IDs differ between OSes (due to extern static allocations)
 
 extern "Rust" {