fix: simulator doesn't fail with long chains (#385)

* fix: simulator doesn't fail with long chains The core issue is that Block is essentially a linked list, so: * dropping it may SO * cloning it is linear and may SO Fix the drop manually and optimize the clone to be O(1) closes #379 * Update version Co-authored-by: Evgeny Kuzyakov <ek@nearprotocol.com>
near · Apr 29, 2021 · 1951284 · 1951284
1 parent 42107dc
commit 1951284
Show file tree

Hide file tree

Showing 5 changed files with 32 additions and 9 deletions.
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/examples/fungible-token/Cargo.lock b/examples/fungible-token/Cargo.lock
diff --git a/near-sdk-sim/Cargo.toml b/near-sdk-sim/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "near-sdk-sim"
-version = "3.1.0"
+version = "3.1.1"
 authors = ["Near Inc <hello@near.org>"]
 edition = "2018"
 license = "GPL-3.0"

diff --git a/near-sdk-sim/README.md b/near-sdk-sim/README.md
@@ -12,6 +12,12 @@ As a first step, you can use this library! With it, you can:
 
 To view this documentation locally, clone this repo and from this folder run `cargo doc --open`.
 
+## Changelog
+
+### `3.1.1`
+
+* Fixed stack overflow for deep chain [PR #385](https://github.com/near/near-sdk-rs/pull/385).
+
 # Getting started
 
 This section will guide you through our suggested approach to adding simulation tests to your project. Want an example? Check out the [Fungible Token Example](https://github.com/near/near-sdk-rs/tree/master/examples/fungible-token).
@@ -22,15 +28,15 @@ Currently this crate depends on a the GitHub repo of [nearcore](https://github.c
 
 ```toml
 [dev-dependencies]
-near-sdk-sim = "=3.1.0"
+near-sdk-sim = "3.1.1"
 
 ```
 
 And update `near-sdk` too:
 
 ```toml
 [dependencies]
-near-sdk = "=3.1.0"
+near-sdk = "3.1.1"
 
 ```
 
@@ -55,8 +61,8 @@ Now in the root of the project (`contract-wrap`), create a new `Cargo.toml`. You
 
 ```toml
 [dev-dependencies]
-near-sdk = "=3.1.0"
-near-sdk-sim = "=3.1.0"
+near-sdk = "3.1.1"
+near-sdk-sim = "3.1.1"
 contract = { path = "./contract" }
 
 [workspace]

diff --git a/near-sdk-sim/src/runtime.rs b/near-sdk-sim/src/runtime.rs
@@ -87,7 +87,7 @@ impl GenesisConfig {
 
 #[derive(Debug, Default, Clone)]
 pub struct Block {
-    prev_block: Option<Box<Block>>,
+    prev_block: Option<Arc<Block>>,
     state_root: CryptoHash,
     gas_burnt: Gas,
     pub epoch_height: EpochHeight,
@@ -97,6 +97,17 @@ pub struct Block {
     pub gas_limit: Gas,
 }
 
+impl Drop for Block {
+    fn drop(&mut self) {
+        // Blocks form a liked list, so the generated recursive drop overflows
+        // the stack. Let's use an explicit loop to avoid that.
+        let mut curr = self.prev_block.take();
+        while let Some(mut next) = curr.and_then(|it| Arc::try_unwrap(it).ok()) {
+            curr = next.prev_block.take();
+        }
+    }
+}
+
 impl Block {
     pub fn genesis(genesis_config: &GenesisConfig) -> Self {
         Self {
@@ -116,7 +127,7 @@ impl Block {
             gas_price: self.gas_price,
             gas_limit: self.gas_limit,
             block_timestamp: self.block_timestamp + 1_000_000_000,
-            prev_block: Some(Box::new(self.clone())),
+            prev_block: Some(Arc::new(self.clone())),
             state_root: new_state_root,
             block_height: self.block_height + 1,
             epoch_height: (self.block_height + 1) / epoch_length,
@@ -517,4 +528,10 @@ mod tests {
         runtime.force_account_update("root".into(), &bob_account);
         assert_eq!(runtime.view_account(&"root").unwrap().locked, 10000);
     }
+
+    #[test]
+    fn can_produce_many_blocks_without_stack_overflow() {
+        let (mut runtime, _signer, _) = init_runtime(None);
+        runtime.produce_blocks(20_000).unwrap();
+    }
 }