fix(ethexe): allocation failure on huge journal returned from runtime (…

…#4397)

ethexe/processor/src/host/mod.rs

@@ -141,7 +141,17 @@ impl InstanceWrapper {
             maybe_instrumented_code,
         );
 
-        self.call("run", arg.encode())
+        // Peaces of resulting journal. Hack to avoid single allocation limit.
+        let ptr_lens: Vec<i64> = self.call("run", arg.encode())?;
+
+        let mut journal = Vec::new();
+
+        for ptr_len in ptr_lens {
+            let journal_chunk: Vec<JournalNote> = self.get_call_output(ptr_len)?;
+            journal.extend(journal_chunk);
+        }
+
+        Ok(journal)
     }
 
     fn call<D: Decode>(&mut self, name: &'static str, input: impl AsRef<[u8]>) -> Result<D> {

ethexe/runtime/src/wasm/api/mod.rs

@@ -46,13 +46,18 @@ fn _run(arg_ptr: i32, arg_len: i32) -> i64 {
     let (program_id, original_code_id, state_root, maybe_instrumented_code) =
         Decode::decode(&mut get_slice(arg_ptr, arg_len)).unwrap();
 
-    let res = run::run(
+    let journal = run::run(
         program_id,
         original_code_id,
         state_root,
         maybe_instrumented_code,
     );
 
+    let chunks = journal.encoded_size() / 32 * 1024 * 1024 + 1; // never zero
+    let chunk_size = (journal.len() / chunks).max(1); // never zero
+
+    let res: Vec<_> = journal.chunks(chunk_size).map(return_val).collect();
+
     return_val(res)
 }