Fix memory leak in os impl

Author: Jules-Bertholet

library/std/src/sys/thread_local/os.rs

@@ -148,14 +148,16 @@ impl<T: 'static, const ALIGN: usize> Storage<T, ALIGN> {
             return ptr::null();
         }
 
+        let value = i.and_then(Option::take).unwrap_or_else(f);
+
         // Manually allocate with the requested alignment
         let layout = Layout::new::<Value<T>>().align_to(ALIGN).unwrap();
         let ptr: *mut Value<T> = (unsafe { crate::alloc::alloc(layout) }).cast();
         if ptr.is_null() {
             crate::alloc::handle_alloc_error(layout);
         }
         unsafe {
-            ptr.write(Value { value: i.and_then(Option::take).unwrap_or_else(f), key });
+            ptr.write(Value { value, key });
         }
 
         // SAFETY:

src/tools/miri/tests/pass/thread_local-panic.rs

@@ -0,0 +1,7 @@
+thread_local! {
+    static LOCAL: u64 = panic!();
+}
+
+fn main() {
+    let _ = std::panic::catch_unwind(|| LOCAL.with(|_| {}));
+}

src/tools/miri/tests/pass/thread_local-panic.stderr

@@ -0,0 +1,5 @@
+
+thread 'main' ($TID) panicked at tests/pass/thread_local-panic.rs:LL:CC:
+explicit panic
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect