Add roundtrip-roundtrip fuzz target.

fuzz/Cargo.toml

@@ -33,3 +33,9 @@ name = "roundtrip"
 path = "fuzz_targets/roundtrip.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "roundtrip_roundtrip"
+path = "fuzz_targets/roundtrip_roundtrip.rs"
+test = false
+doc = false

fuzz/fuzz_targets/roundtrip_roundtrip.rs

@@ -0,0 +1,14 @@
+#![no_main]
+use libfuzzer_sys::fuzz_target;
+
+use waffle::Module;
+
+fuzz_target!(|module: wasm_smith::Module| {
+    let _ = env_logger::try_init();
+    log::debug!("original module: {:?}", module);
+    let orig_bytes = module.to_bytes();
+    let parsed_module = Module::from_wasm_bytes(&orig_bytes[..]).unwrap();
+    let roundtrip_bytes = parsed_module.to_wasm_bytes();
+    let parsed_roundtrip_module = Module::from_wasm_bytes(&roundtrip_bytes[..]).unwrap();
+    let _ = parsed_roundtrip_module.to_wasm_bytes();
+});

src/backend/final.rs

@@ -169,6 +169,7 @@ pub fn produce_func_wasm<FT: FuncTypeSink>(
     for operator in &body.operators {
         ctx.translate(operator, locations);
     }
+    wasm.operators.push(wasm_encoder::Instruction::End);
 
     wasm
 }