From cc449351ae015f947c81271106b990387dcd9d8a Mon Sep 17 00:00:00 2001
From: arvidn <arvid@libtorrent.org>
Date: Fri, 3 Jan 2025 16:26:42 +0100
Subject: [PATCH] extend serializer fuzzer, to ensure the serialized form is
 valid and round-trips correctly

---
 fuzz/fuzz_targets/node_eq.rs    | 12 ++++++++++++
 fuzz/fuzz_targets/serializer.rs | 15 ++++++++++++---
 2 files changed, 24 insertions(+), 3 deletions(-)
 create mode 100644 fuzz/fuzz_targets/node_eq.rs

diff --git a/fuzz/fuzz_targets/node_eq.rs b/fuzz/fuzz_targets/node_eq.rs
new file mode 100644
index 00000000..a4c87a2b
--- /dev/null
+++ b/fuzz/fuzz_targets/node_eq.rs
@@ -0,0 +1,12 @@
+use clvmr::{Allocator, NodePtr, SExp};
+
+/// compare two CLVM trees. Returns true if they are identical, false otherwise
+pub fn node_eq(allocator: &Allocator, s1: NodePtr, s2: NodePtr) -> bool {
+    match (allocator.sexp(s1), allocator.sexp(s2)) {
+        (SExp::Pair(s1a, s1b), SExp::Pair(s2a, s2b)) => {
+            node_eq(allocator, s1a, s2a) && node_eq(allocator, s1b, s2b)
+        }
+        (SExp::Atom, SExp::Atom) => allocator.atom_eq(s1, s2),
+        _ => false,
+    }
+}
diff --git a/fuzz/fuzz_targets/serializer.rs b/fuzz/fuzz_targets/serializer.rs
index aedba3d4..2e58a2e6 100644
--- a/fuzz/fuzz_targets/serializer.rs
+++ b/fuzz/fuzz_targets/serializer.rs
@@ -1,9 +1,11 @@
 #![no_main]
 
 mod fuzzing_utils;
+mod node_eq;
 
 use clvmr::allocator::Allocator;
-use clvmr::serde::{node_to_bytes_backrefs, Serializer};
+use clvmr::serde::{node_from_bytes_backrefs, node_to_bytes_backrefs, Serializer};
+use node_eq::node_eq;
 
 use libfuzzer_sys::fuzz_target;
 
@@ -22,9 +24,16 @@ fn do_fuzz(data: &[u8], short_atoms: bool) {
     assert!(done);
     let b2 = ser.into_inner();
 
-    if b1 != b2 {
-        panic!("b1 and b2 do not match");
+    {
+        // make sure both serializations are valid, and can be parsed to produce
+        // the same tree
+        let b1 = node_from_bytes_backrefs(&mut allocator, &b1).unwrap();
+        let b2 = node_from_bytes_backrefs(&mut allocator, &b2).unwrap();
+        assert!(node_eq(&allocator, b1, program));
+        assert!(node_eq(&allocator, b1, b2));
     }
+
+    assert_eq!(b1, b2);
 }
 
 fuzz_target!(|data: &[u8]| {