From fd87c238fca2414ed1fa7a18a9ab29ecd53b0208 Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Fri, 5 Feb 2021 23:14:42 -0600
Subject: [PATCH] Don't panic when can't __del__ object

---
 vm/src/lib.rs        | 2 +-
 vm/src/pyobjectrc.rs | 5 ++++-
 vm/src/vm.rs         | 8 +++-----
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/vm/src/lib.rs b/vm/src/lib.rs
index 9764a8ce53..c511b73b1e 100644
--- a/vm/src/lib.rs
+++ b/vm/src/lib.rs
@@ -54,7 +54,7 @@ pub mod frame;
 mod frozen;
 pub mod function;
 pub mod import;
-mod iterator;
+pub mod iterator;
 mod py_io;
 pub mod py_serde;
 pub mod pyobject;
diff --git a/vm/src/pyobjectrc.rs b/vm/src/pyobjectrc.rs
index bc973a2844..e7222eaaed 100644
--- a/vm/src/pyobjectrc.rs
+++ b/vm/src/pyobjectrc.rs
@@ -307,7 +307,7 @@ impl Drop for PyObjectRef {
         // CPython-compatible drop implementation
         let zelf = self.clone();
         if let Some(del_slot) = self.class().mro_find_map(|cls| cls.slots.del.load()) {
-            crate::vm::thread::with_vm(&zelf, |vm| {
+            let ret = crate::vm::thread::with_vm(&zelf, |vm| {
                 if let Err(e) = del_slot(&zelf, vm) {
                     // exception in del will be ignored but printed
                     print!("Exception ignored in: ",);
@@ -327,6 +327,9 @@ impl Drop for PyObjectRef {
                     }
                 }
             });
+            if ret.is_none() {
+                warn!("couldn't run __del__ method for object")
+            }
         }
 
         // __del__ might have resurrected the object at this point, but that's fine,
diff --git a/vm/src/vm.rs b/vm/src/vm.rs
index 7ab6524219..ffafe0c8c4 100644
--- a/vm/src/vm.rs
+++ b/vm/src/vm.rs
@@ -86,7 +86,7 @@ pub(crate) mod thread {
         })
     }
 
-    pub fn with_vm<F, R>(obj: &PyObjectRef, f: F) -> R
+    pub fn with_vm<F, R>(obj: &PyObjectRef, f: F) -> Option<R>
     where
         F: Fn(&VirtualMachine) -> R,
     {
@@ -101,14 +101,12 @@ pub(crate) mod thread {
                     debug_assert!(vm_owns_obj(x));
                     x
                 }
-                Err(mut others) => others
-                    .find(|x| vm_owns_obj(*x))
-                    .unwrap_or_else(|| panic!("can't get a vm for {:?}; none on stack", obj)),
+                Err(mut others) => others.find(|x| vm_owns_obj(*x))?,
             };
             // SAFETY: all references in VM_STACK should be valid, and should not be changed or moved
             // at least until this function returns and the stack unwinds to an enter_vm() call
             let vm = unsafe { intp.as_ref() };
-            f(vm)
+            Some(f(vm))
         })
     }
 }