From 4c5bf193431dd48ae8d0be9e0ee8b0194592a95f Mon Sep 17 00:00:00 2001
From: Mark McCaskey <mark@wasmer.io>
Date: Tue, 8 Sep 2020 13:31:14 -0700
Subject: [PATCH] Fix bug relating to type conversion in function calls

---
 CHANGELOG.md                      |  1 +
 lib/api/src/externals/function.rs | 30 +++++++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d24118bfb4..68f1ad30a01 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 # Changelog
 
 ## **[Unreleased]**
+- [#1602](https://github.com/wasmerio/wasmer/pull/1602) Fix panic when calling host functions with negative numbers in certain situations
 - [#1590](https://github.com/wasmerio/wasmer/pull/1590) Fix soundness issue in API of vm::Global
 - [#1566](https://github.com/wasmerio/wasmer/pull/1566) Add support for opening special Unix files to the WASI FS
 
diff --git a/lib/api/src/externals/function.rs b/lib/api/src/externals/function.rs
index b0cc211aa81..b1cd280563a 100644
--- a/lib/api/src/externals/function.rs
+++ b/lib/api/src/externals/function.rs
@@ -621,11 +621,39 @@ mod inner {
         };
     }
 
+    macro_rules! from_to_native_wasm_type_same_size {
+        ( $( $type:ty => $native_type:ty ),* ) => {
+            $(
+                #[allow(clippy::use_self)]
+                unsafe impl FromToNativeWasmType for $type {
+                    type Native = $native_type;
+
+                    #[inline]
+                    fn from_native(native: Self::Native) -> Self {
+                        unsafe {
+                            std::mem::transmute::<$native_type, $type>(native)
+                        }
+                    }
+
+                    #[inline]
+                    fn to_native(self) -> Self::Native {
+                        unsafe {
+                            std::mem::transmute::<$type, $native_type>(self)
+                        }
+                    }
+                }
+            )*
+        };
+    }
+
     from_to_native_wasm_type!(
         i8 => i32,
         u8 => i32,
         i16 => i32,
-        u16 => i32,
+        u16 => i32
+    );
+
+    from_to_native_wasm_type_same_size!(
         i32 => i32,
         u32 => i32,
         i64 => i64,