skip deallocating main-thread TLS backing memory

Author: max-heller

src/concurrency/thread.rs

@@ -1070,14 +1070,23 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
         thread.state = ThreadState::Terminated;
 
         let current_span = this.machine.current_span();
-        for ptr in
-            this.machine.threads.thread_terminated(this.machine.data_race.as_mut(), current_span)
-        {
-            if let Some(alloc) = ptr.provenance.get_alloc_id() {
-                trace!("Main thread thread-local static stored as static root: {:?}", alloc);
-                this.machine.static_roots.push(alloc);
+        let thread_local_allocations = this.machine.threads.thread_terminated(
+            this.machine.data_race.as_mut(),
+            current_span,
+        );
+        match this.get_active_thread_id() {
+            // For main thread, add thread-local statics to static roots and skip deallocating
+            // backing memory
+            ThreadId(0) => for ptr in thread_local_allocations {
+                if let Some(alloc) = ptr.provenance.get_alloc_id() {
+                    trace!("Main thread thread-local static stored as static root: {:?}", alloc);
+                    this.machine.static_roots.push(alloc);
+                }
+            }
+            // Deallocate backing memory of thread-local statics
+            ThreadId(_) => for ptr in thread_local_allocations {
+                this.deallocate_ptr(ptr.into(), None, MiriMemoryKind::Tls.into())?;
             }
-            this.deallocate_ptr(ptr.into(), None, MiriMemoryKind::Tls.into())?;
         }
         Ok(())
     }