optionally burn

Author: Stebalien

fvm/src/kernel/default.rs

@@ -11,7 +11,6 @@ use filecoin_proofs_api::{self as proofs, ProverId, PublicReplicaInfo, SectorId}
 use fvm_ipld_blockstore::Blockstore;
 use fvm_ipld_encoding::{bytes_32, IPLD_RAW};
 use fvm_shared::address::Payload;
-use fvm_shared::bigint::Zero;
 use fvm_shared::chainid::ChainID;
 use fvm_shared::consensus::ConsensusFault;
 use fvm_shared::crypto::signature;
@@ -244,7 +243,7 @@ where
         t.record(Ok(self.get_self()?.map(|a| a.balance).unwrap_or_default()))
     }
 
-    fn self_destruct(&mut self) -> Result<()> {
+    fn self_destruct(&mut self, burn_unspent: bool) -> Result<()> {
         if self.read_only {
             return Err(syscall_error!(ReadOnly; "cannot self-destruct when read-only").into());
         }
@@ -263,7 +262,12 @@ where
         // 2. If we ever decide to allow code on method 0, allowing transfers here would be
         //    unfortunate.
         let balance = self.current_balance()?;
-        if balance != TokenAmount::zero() {
+        if !balance.is_zero() {
+            if !burn_unspent {
+                return Err(
+                    syscall_error!(IllegalOperation; "self-destruct with unspent funds").into(),
+                );
+            }
             self.call_manager
                 .transfer(self.actor_id, BURNT_FUNDS_ACTOR_ID, &balance)
                 .or_fatal()?;

fvm/src/kernel/mod.rs

@@ -176,8 +176,8 @@ pub trait SelfOps: IpldBlockOps {
     /// The balance of the receiver.
     fn current_balance(&self) -> Result<TokenAmount>;
 
-    /// Deletes the executing actor from the state tree, burning any remaining balance.
-    fn self_destruct(&mut self) -> Result<()>;
+    /// Deletes the executing actor from the state tree, burning any remaining balance if requested.
+    fn self_destruct(&mut self, burn_unspent: bool) -> Result<()>;
 }
 
 /// Actors operations whose scope of action is actors other than the calling

fvm/src/syscalls/sself.rs

@@ -33,7 +33,7 @@ pub fn current_balance(context: Context<'_, impl Kernel>) -> Result<sys::TokenAm
         .or_fatal()
 }
 
-pub fn self_destruct(context: Context<'_, impl Kernel>) -> Result<()> {
-    context.kernel.self_destruct()?;
+pub fn self_destruct(context: Context<'_, impl Kernel>, burn_unspent: u32) -> Result<()> {
+    context.kernel.self_destruct(burn_unspent > 0)?;
     Ok(())
 }

sdk/src/error.rs

@@ -15,8 +15,12 @@ pub enum StateUpdateError {
 }
 
 #[derive(Copy, Clone, Debug, Error, Eq, PartialEq)]
-#[error("current execution context is read-only")]
-pub struct ActorDeleteError;
+pub enum ActorDeleteError {
+    #[error("cannot self-destruct when read-only")]
+    ReadOnly,
+    #[error("actor did not request unspent funds to be burnt")]
+    UnspentFunds,
+}
 
 #[derive(Copy, Clone, Debug, Error, Eq, PartialEq)]
 pub enum EpochBoundsError {

sdk/src/sself.rs

@@ -53,10 +53,11 @@ pub fn current_balance() -> TokenAmount {
 }
 
 /// Destroys the calling actor, burning any remaining balance.
-pub fn self_destruct() -> Result<(), ActorDeleteError> {
+pub fn self_destruct(burn_funds: bool) -> Result<(), ActorDeleteError> {
     unsafe {
-        sys::sself::self_destruct().map_err(|e| match e {
-            ErrorNumber::ReadOnly => ActorDeleteError,
+        sys::sself::self_destruct(burn_funds).map_err(|e| match e {
+            ErrorNumber::IllegalOperation => ActorDeleteError::UnspentFunds,
+            ErrorNumber::ReadOnly => ActorDeleteError::ReadOnly,
             _ => panic!("unexpected error from `self::self_destruct` syscall: {}", e),
         })
     }

sdk/src/sys/sself.rs

@@ -49,21 +49,19 @@ super::fvm_syscalls! {
     /// None.
     pub fn current_balance() -> Result<super::TokenAmount>;
 
-    /// Destroys the calling actor, sending its current balance
-    /// to the supplied address, which cannot be itself.
-    ///
-    /// Fails when calling actor has a non zero balance and the beneficiary doesn't
-    /// exist or is the actor being deleted.
+    /// Destroys the calling actor. If `burn_funds` is true, any unspent balance will be burnt
+    /// (destroyed). Otherwise, if `burnt_funds` is false and there are unspent funds, this syscall
+    /// will fail.
     ///
     /// # Arguments
     ///
-    /// - `addr_off` and `addr_len` specify the location and length of beneficiary's address in wasm
-    ///   memory.
+    /// - `burn_funds` must be true to delete an actor with unspent funds.
     ///
     /// # Errors
     ///
-    /// | Error         | Reason                                    |
-    /// |---------------|-------------------------------------------|
-    /// | [`ReadOnly`]  | the actor is executing in read-only mode  |
-    pub fn self_destruct() -> Result<()>;
+    /// | Error                 | Reason                                    |
+    /// |-----------------------|-------------------------------------------|
+    /// | [`IllegalOperation`]  | the actor has unspent funds               |
+    /// | [`ReadOnly`]          | the actor is executing in read-only mode  |
+    pub fn self_destruct(burn_funds: bool) -> Result<()>;
 }

testing/conformance/src/vm.rs

@@ -529,8 +529,8 @@ where
         self.0.current_balance()
     }
 
-    fn self_destruct(&mut self) -> Result<()> {
-        self.0.self_destruct()
+    fn self_destruct(&mut self, burn_unspent: bool) -> Result<()> {
+        self.0.self_destruct(burn_unspent)
     }
 }
 

testing/test_actors/actors/fil-readonly-actor/src/actor.rs

@@ -10,7 +10,7 @@ use fvm_shared::econ::TokenAmount;
 use fvm_shared::event::{Entry, Flags};
 use fvm_shared::sys::SendFlags;
 use fvm_shared::METHOD_SEND;
-use sdk::error::StateUpdateError;
+use sdk::error::{ActorDeleteError, StateUpdateError};
 use sdk::sys::ErrorNumber;
 
 /// Placeholder invoke for testing
@@ -159,7 +159,10 @@ fn invoke_method(blk: u32, method: u64) -> u32 {
             assert_eq!(err, ErrorNumber::ReadOnly);
 
             // Should not be able to delete self.
-            sdk::sself::self_destruct().expect_err("deleted self while read-only");
+            assert_eq!(
+                sdk::sself::self_destruct(true).unwrap_err(),
+                ActorDeleteError::ReadOnly
+            );
         }
         4 => {
             assert!(sdk::vm::read_only());

testing/test_actors/actors/fil-sself-actor/src/actor.rs

@@ -5,7 +5,7 @@ use cid::Cid;
 use fvm_ipld_encoding::{to_vec, DAG_CBOR};
 use fvm_sdk as sdk;
 use fvm_shared::econ::TokenAmount;
-use sdk::error::{StateReadError, StateUpdateError};
+use sdk::error::{ActorDeleteError, StateReadError, StateUpdateError};
 
 #[no_mangle]
 pub fn invoke(_: u32) -> u32 {
@@ -30,8 +30,14 @@ pub fn invoke(_: u32) -> u32 {
     let balance = sdk::sself::current_balance();
     assert_eq!(TokenAmount::from_nano(1_000_000), balance);
 
-    // now lets destroy the actor, burning the funds.
-    sdk::sself::self_destruct().unwrap();
+    // Now destroy the actor without burning funds. This should fail because we have unspent funds.
+    assert_eq!(
+        sdk::sself::self_destruct(false).unwrap_err(),
+        ActorDeleteError::UnspentFunds
+    );
+
+    // Now lets destroy the actor, burning the funds.
+    sdk::sself::self_destruct(true).unwrap();
 
     // test that root/set_root/self_destruct fail when the actor has been deleted
     // and balance is 0
@@ -43,7 +49,7 @@ pub fn invoke(_: u32) -> u32 {
     assert_eq!(TokenAmount::from_nano(0), sdk::sself::current_balance());
 
     // calling destroy on an already destroyed actor should succeed (no-op)
-    sdk::sself::self_destruct().expect("deleting an already deleted actor should succeed");
+    sdk::sself::self_destruct(false).expect("deleting an already deleted actor should succeed");
 
     #[cfg(coverage)]
     sdk::debug::store_artifact("sself_actor.profraw", minicov::capture_coverage());