deallocate old environ

Author: pvdrz

src/machine.rs

@@ -85,7 +85,7 @@ pub struct MemoryExtra<'tcx> {
     /// (helps for debugging memory leaks).
     tracked_alloc_id: Option<AllocId>,
 
-    /// Place where the `environ` static is stored.
+    /// Place where the `environ` static is stored. Its value should not change after initialization.
     pub(crate) environ: Option<MPlaceTy<'tcx, Tag>>,
 }
 

src/shims/env.rs

@@ -157,6 +157,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
     fn update_environ(&mut self) -> InterpResult<'tcx> {
         let this = self.eval_context_mut();
+        // Deallocate the old value for environ, if it exists.
+        if let Some(environ) = this.memory.extra.environ {
+            let old_vars_ptr = this.force_ptr(this.read_scalar(environ.into())?.not_undef()?)?;
+            this.memory.deallocate(old_vars_ptr, None, MiriMemoryKind::Machine.into())?;
+        }
         // Collect all the pointers to each variable in a vector.
         let mut vars: Vec<Scalar<Tag>> = this.machine.env_vars.map.values().map(|&ptr| ptr.into()).collect();
         // Add the trailing null pointer.