From a8d4978863b3844ad01d7ab88d527cc28f795024 Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Fri, 31 Jan 2020 19:21:33 -0800
Subject: [PATCH] Disable cranelift's verifier by default

The intention of the `wasmtime` crate was to disable this verifier by
default, but it looks like cranelift actually has it turned on by
default which was making our documentation incorrect!

This was discovered by seeing a number of timeouts when fuzzing. The
debug verifier is great for fuzzing, however, so fuzzing is updated to
enable this unconditionally, meaning we'll still have timeouts. For
general users though this should make the documentation correct that the
`wasmtime` crate, by default, disables the debug verifier.
---
 crates/api/src/runtime.rs     |  5 +++++
 crates/fuzzing/src/oracles.rs | 10 ++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/crates/api/src/runtime.rs b/crates/api/src/runtime.rs
index 3475261ce9a1..bbb92c2d2618 100644
--- a/crates/api/src/runtime.rs
+++ b/crates/api/src/runtime.rs
@@ -34,6 +34,11 @@ impl Config {
             .enable("avoid_div_traps")
             .expect("should be valid flag");
 
+        // Invert cranelift's default-on verification to instead default off.
+        flags
+            .set("enable_verifier", "false")
+            .expect("should be valid flag");
+
         Config {
             debug_info: false,
             features: Default::default(),
diff --git a/crates/fuzzing/src/oracles.rs b/crates/fuzzing/src/oracles.rs
index 5b1b79ed5abc..60fb6087cd90 100644
--- a/crates/fuzzing/src/oracles.rs
+++ b/crates/fuzzing/src/oracles.rs
@@ -25,6 +25,7 @@ use wasmtime::*;
 pub fn instantiate(wasm: &[u8], strategy: Strategy) {
     let mut config = Config::new();
     config
+        .cranelift_debug_verifier(true)
         .strategy(strategy)
         .expect("failed to enable lightbeam");
     let engine = Engine::new(&config);
@@ -60,7 +61,10 @@ pub fn instantiate(wasm: &[u8], strategy: Strategy) {
 /// You can control which compiler is used via passing a `Strategy`.
 pub fn compile(wasm: &[u8], strategy: Strategy) {
     let mut config = Config::new();
-    config.strategy(strategy).unwrap();
+    config
+        .cranelift_debug_verifier(true)
+        .strategy(strategy)
+        .unwrap();
     let engine = Engine::new(&config);
     let store = Store::new(&engine);
     let _ = Module::new(&store, wasm);
@@ -254,7 +258,9 @@ pub fn make_api_calls(api: crate::generators::api::ApiCalls) {
         match call {
             ApiCall::ConfigNew => {
                 assert!(config.is_none());
-                config = Some(Config::new());
+                let mut cfg = Config::new();
+                cfg.cranelift_debug_verifier(true);
+                config = Some(cfg);
             }
 
             ApiCall::ConfigDebugInfo(b) => {