From e3f34f319cc9eb5cc4f87074a313f98c1dff70ca Mon Sep 17 00:00:00 2001
From: Peter Marheine <peter@taricorp.net>
Date: Wed, 6 Dec 2023 21:16:52 +1100
Subject: [PATCH] Correct C return type for lua_error

The definition of lua_error in all of Lua 5.1 through 5.4 says lua_error
returns int, but the Rust definition of the same function treats it as
void (because it's known not to return). This causes link-time errors when
building for wasm targets because the wasm linker is aware of function return
types and errors out if they differ between definition and declaration.
---
 mlua-sys/src/lua51/lua.rs | 11 ++++++++++-
 mlua-sys/src/lua52/lua.rs | 11 ++++++++++-
 mlua-sys/src/lua53/lua.rs | 11 ++++++++++-
 mlua-sys/src/lua54/lua.rs | 11 ++++++++++-
 4 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/mlua-sys/src/lua51/lua.rs b/mlua-sys/src/lua51/lua.rs
index 925e9c7..5cd351d 100644
--- a/mlua-sys/src/lua51/lua.rs
+++ b/mlua-sys/src/lua51/lua.rs
@@ -228,13 +228,22 @@ extern "C-unwind" {
 //
 #[cfg_attr(all(windows, raw_dylib), link(name = "lua51", kind = "raw-dylib"))]
 extern "C-unwind" {
-    pub fn lua_error(L: *mut lua_State) -> !;
+    #[link_name = "lua_error"]
+    fn lua_error_(L: *mut lua_State) -> c_int;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_concat(L: *mut lua_State, n: c_int);
     pub fn lua_getallocf(L: *mut lua_State, ud: *mut *mut c_void) -> lua_Alloc;
     pub fn lua_setallocf(L: *mut lua_State, f: lua_Alloc, ud: *mut c_void);
 }
 
+// lua_error does not return but is declared to return int, and Rust translates
+// ! to void which can cause link-time errors if the platform linker is aware
+// of return types and requires they match (for example: wasm does this).
+pub unsafe fn lua_error(L: *mut lua_State) -> ! {
+    lua_error_(L);
+    unreachable!();
+}
+
 //
 // Some useful macros (implemented as Rust functions)
 //
diff --git a/mlua-sys/src/lua52/lua.rs b/mlua-sys/src/lua52/lua.rs
index 760140b..d668d67 100644
--- a/mlua-sys/src/lua52/lua.rs
+++ b/mlua-sys/src/lua52/lua.rs
@@ -308,7 +308,8 @@ extern "C-unwind" {
     //
     // Miscellaneous functions
     //
-    pub fn lua_error(L: *mut lua_State) -> !;
+    #[link_name = "lua_error"]
+    fn lua_error_(L: *mut lua_State) -> c_int;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_concat(L: *mut lua_State, n: c_int);
     pub fn lua_len(L: *mut lua_State, idx: c_int);
@@ -316,6 +317,14 @@ extern "C-unwind" {
     pub fn lua_setallocf(L: *mut lua_State, f: lua_Alloc, ud: *mut c_void);
 }
 
+// lua_error does not return but is declared to return int, and Rust translates
+// ! to void which can cause link-time errors if the platform linker is aware
+// of return types and requires they match (for example: wasm does this).
+pub unsafe fn lua_error(L: *mut lua_State) -> ! {
+    lua_error_(L);
+    unreachable!();
+}
+
 //
 // Some useful macros (implemented as Rust functions)
 //
diff --git a/mlua-sys/src/lua53/lua.rs b/mlua-sys/src/lua53/lua.rs
index d918de4..393ff3c 100644
--- a/mlua-sys/src/lua53/lua.rs
+++ b/mlua-sys/src/lua53/lua.rs
@@ -314,7 +314,8 @@ extern "C-unwind" {
     //
     // Miscellaneous functions
     //
-    pub fn lua_error(L: *mut lua_State) -> !;
+    #[link_name = "lua_error"]
+    fn lua_error_(L: *mut lua_State) -> c_int;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_concat(L: *mut lua_State, n: c_int);
     pub fn lua_len(L: *mut lua_State, idx: c_int);
@@ -323,6 +324,14 @@ extern "C-unwind" {
     pub fn lua_setallocf(L: *mut lua_State, f: lua_Alloc, ud: *mut c_void);
 }
 
+// lua_error does not return but is declared to return int, and Rust translates
+// ! to void which can cause link-time errors if the platform linker is aware
+// of return types and requires they match (for example: wasm does this).
+pub unsafe fn lua_error(L: *mut lua_State) -> ! {
+    lua_error_(L);
+    unreachable!();
+}
+
 //
 // Some useful macros (implemented as Rust functions)
 //
diff --git a/mlua-sys/src/lua54/lua.rs b/mlua-sys/src/lua54/lua.rs
index 7eab2af..b134866 100644
--- a/mlua-sys/src/lua54/lua.rs
+++ b/mlua-sys/src/lua54/lua.rs
@@ -343,7 +343,8 @@ extern "C-unwind" {
     //
     // Miscellaneous functions
     //
-    pub fn lua_error(L: *mut lua_State) -> !;
+    #[link_name = "lua_error"]
+    fn lua_error_(L: *mut lua_State) -> c_int;
     pub fn lua_next(L: *mut lua_State, idx: c_int) -> c_int;
     pub fn lua_concat(L: *mut lua_State, n: c_int);
     pub fn lua_len(L: *mut lua_State, idx: c_int);
@@ -355,6 +356,14 @@ extern "C-unwind" {
     pub fn lua_closeslot(L: *mut lua_State, idx: c_int);
 }
 
+// lua_error does not return but is declared to return int, and Rust translates
+// ! to void which can cause link-time errors if the platform linker is aware
+// of return types and requires they match (for example: wasm does this).
+pub unsafe fn lua_error(L: *mut lua_State) -> ! {
+    lua_error_(L);
+    unreachable!();
+}
+
 //
 // Some useful macros (implemented as Rust functions)
 //