From 727e36de00b4e87bfa24586ea6bb7136b2dbce7f Mon Sep 17 00:00:00 2001
From: Pierre Krieger <pierre.krieger1708@gmail.com>
Date: Fri, 10 Feb 2023 15:14:10 +0100
Subject: [PATCH] Add a basic Wasm VM test (#159)

---
 Cargo.lock               | 43 +++++++++++++++++++++++++++++++++
 Cargo.toml               |  1 +
 src/executor/vm.rs       |  2 +-
 src/executor/vm/tests.rs | 51 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index 5a4747d861..e238a416a9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1407,6 +1407,12 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
+[[package]]
+name = "leb128"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "884e2677b40cc8c339eaefcb701c32ef1fd2493d71118dc0ca4b6a736c93bd67"
+
 [[package]]
 name = "libc"
 version = "0.2.139"
@@ -2391,6 +2397,7 @@ dependencies = [
  "twox-hash",
  "wasmi",
  "wasmtime",
+ "wat",
 ]
 
 [[package]]
@@ -2797,6 +2804,12 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dcc811dc4066ac62f84f11307873c4850cb653bfa9b1719cee2bd2204a4bc5dd"
 
+[[package]]
+name = "unicode-width"
+version = "0.1.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c0edd1e5b14653f783770bce4a4dabb4a5108a5370a5f5d8cfe8710c361f6c8b"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.2"
@@ -2924,6 +2937,15 @@ version = "0.2.78"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0237232789cf037d5480773fe568aac745bfe2afbc11a863e97901780a6b47cc"
 
+[[package]]
+name = "wasm-encoder"
+version = "0.23.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c3e4bc09095436c8e7584d86d33e6c3ee67045af8fb262cbb9cc321de553428"
+dependencies = [
+ "leb128",
+]
+
 [[package]]
 name = "wasmi"
 version = "0.9.1"
@@ -3128,6 +3150,27 @@ dependencies = [
  "wasmparser",
 ]
 
+[[package]]
+name = "wast"
+version = "53.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8244fa24196b1d8fd3ca4a96a3a164c40f846498c5deab6caf414c67340ca4af"
+dependencies = [
+ "leb128",
+ "memchr",
+ "unicode-width",
+ "wasm-encoder",
+]
+
+[[package]]
+name = "wat"
+version = "1.0.58"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4620f1059add6dad511decb9d5d88b4a0a0d3e2e315ed34f79b0dc0dce18aa4b"
+dependencies = [
+ "wast",
+]
+
 [[package]]
 name = "web-sys"
 version = "0.3.55"
diff --git a/Cargo.toml b/Cargo.toml
index c580494ab6..753cdd4cbc 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -107,6 +107,7 @@ wasmtime = { version = "3.0.0", default-features = false, features = ["async", "
 async-std = "1.12.0"
 criterion = "0.4.0"
 tempfile = "3.3.0"
+wat = "1.0.58"
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
diff --git a/src/executor/vm.rs b/src/executor/vm.rs
index 083b9683e7..7ee1022593 100644
--- a/src/executor/vm.rs
+++ b/src/executor/vm.rs
@@ -494,7 +494,7 @@ impl TryFrom<wasmi::Signature> for Signature {
 }
 
 /// Value that a Wasm function can accept or produce.
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum WasmValue {
     /// A 32-bits integer. There is no fundamental difference between signed and unsigned
     /// integer, and the signed-ness should be determined depending on the context.
diff --git a/src/executor/vm/tests.rs b/src/executor/vm/tests.rs
index c6bd011ae0..a48f80d02e 100644
--- a/src/executor/vm/tests.rs
+++ b/src/executor/vm/tests.rs
@@ -17,6 +17,8 @@
 
 #![cfg(test)]
 
+use core::iter;
+
 #[test]
 fn is_send() {
     // Makes sure that the virtual machine types implement `Send`.
@@ -117,3 +119,52 @@ fn unsupported_type() {
         assert!(super::VirtualMachinePrototype::new(&module2, |_, _, _| Ok(0)).is_err());
     }
 }
+
+#[test]
+fn basic_host_function_return_value_works() {
+    let module_bytes = wat::parse_str(
+        r#"
+    (module
+        (import "host" "hello" (func $host_hello (param i32) (result i32)))
+        (import "env" "memory" (memory $mem 0 4096))
+        (func (export "hello") (result i32)
+            (call $host_hello (i32.const 3))
+        )
+    )
+    "#,
+    )
+    .unwrap();
+
+    for exec_hint in iter::once(super::ExecHint::ForceWasmi)
+        .chain(super::ExecHint::force_wasmtime_if_available().into_iter())
+    {
+        let module = super::Module::new(&module_bytes, exec_hint).unwrap();
+
+        let prototype = super::VirtualMachinePrototype::new(&module, |_, _, _| Ok(0)).unwrap();
+
+        let mut vm = prototype
+            .start(super::HeapPages::new(1024), "hello", &[])
+            .unwrap();
+
+        let mut resume_value = None;
+        loop {
+            match vm.run(resume_value) {
+                Ok(super::ExecOutcome::Finished {
+                    return_value: Ok(value),
+                }) => {
+                    assert_eq!(value, Some(super::WasmValue::I32(3)));
+                    break;
+                }
+                Ok(super::ExecOutcome::Finished {
+                    return_value: Err(_),
+                }) => panic!(),
+                Ok(super::ExecOutcome::Interrupted { id: 0, params }) => {
+                    assert_eq!(params, vec![super::WasmValue::I32(3)]);
+                    resume_value = Some(super::WasmValue::I32(3));
+                }
+                Ok(super::ExecOutcome::Interrupted { .. }) => panic!(),
+                Err(_) => panic!(),
+            }
+        }
+    }
+}