Handle uninit data in pthread_condattr_destroy

src/shims/posix/sync.rs

@@ -189,6 +189,14 @@ fn condattr_set_clock_id<'mir, 'tcx: 'mir>(
     ecx.write_scalar_at_offset(attr_op, 0, clock_id, ecx.machine.layouts.i32)
 }
 
+fn condattr_deinit_clock_id<'mir, 'tcx: 'mir>(
+    ecx: &mut MiriEvalContext<'mir, 'tcx>,
+    attr_op: &OpTy<'tcx, Tag>,
+) -> InterpResult<'tcx, ()> {
+    let layout = layout_of_maybe_uninit(ecx.tcx, ecx.machine.layouts.i32.ty);
+    ecx.write_scalar_at_offset(attr_op, 0, ScalarMaybeUninit::Uninit, layout)
+}
+
 // pthread_cond_t
 
 // Our chosen memory layout for the emulated conditional variable (does not have
@@ -652,7 +660,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
     fn pthread_condattr_destroy(&mut self, attr_op: &OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
 
-        condattr_set_clock_id(this, attr_op, ScalarMaybeUninit::Uninit)?;
+        condattr_get_clock_id(this, attr_op)?.check_init()?;
+
+        condattr_deinit_clock_id(this, attr_op)?;
 
         Ok(0)
     }

tests/compile-fail/sync/libc_pthread_condattr_double_destroy.rs

@@ -0,0 +1,19 @@
+// ignore-windows: No libc on Windows
+#![feature(rustc_private)]
+
+/// Test that destroying a pthread_condattr twice fails, even without a check for number validity
+extern crate libc;
+
+fn main() {
+    unsafe {
+        use core::mem::MaybeUninit;
+        let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit();
+
+        libc::pthread_condattr_init(attr.as_mut_ptr());
+
+        libc::pthread_condattr_destroy(attr.as_mut_ptr());
+
+        libc::pthread_condattr_destroy(attr.as_mut_ptr());
+        //~^ Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+    }
+}

tests/run-pass/concurrency/pthread_condattr_init.rs

@@ -0,0 +1,20 @@
+// ignore-windows: No libc on Windows
+// compile-flags: -Zmiri-check-number-validity
+
+#![feature(rustc_private)]
+
+/// Test that pthread_condattr_destroy doesn't trigger a number validity error.
+extern crate libc;
+
+fn main() {
+    unsafe {
+        use core::mem::MaybeUninit;
+        let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit();
+
+        let r = libc::pthread_condattr_init(attr.as_mut_ptr());
+        assert_eq!(r, 0);
+
+        let r = libc::pthread_condattr_destroy(attr.as_mut_ptr());
+        assert_eq!(r, 0);
+    }
+}