Merge pull request #144 from NordSecurity/LLT-6597_backport_movable_reference_fix

[Backport #143] Fix callback vtable lifetime

Author: Jauler

.github/workflows/cs.yml

@@ -2,9 +2,9 @@ name: C#
 
 on:
   push:
-    branches: [ "main" ]
+    branches: [ "main", "main-v0.28.3" ]
   pull_request:
-    branches: [ "main" ]
+    branches: [ "main", "main-v0.28.3" ]
 
 env:
   CARGO_TERM_COLOR: always

CHANGELOG.md

@@ -1,5 +1,8 @@
 ### UNRELEASED
 
+### v0.9.2+v0.28.3
+- Fix vtable callback lifetimes
+
 ### v0.9.1+v0.28.3
 - Add calling convention cdecl to DllImport
 - User type "String" shadows native type System.String [#110](https://github.com/NordSecurity/uniffi-bindgen-cs/issues/110)

bindgen/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "uniffi-bindgen-cs"
-version = "0.9.0+v0.28.3"
+version = "0.9.2+v0.28.3"
 edition = "2021"
 
 [lib]
@@ -28,4 +28,4 @@ toml = "0.5"
 
 uniffi_bindgen.workspace = true
 uniffi_meta.workspace = true
-uniffi_udl.workspace = true
+uniffi_udl.workspace = true

bindgen/src/gen_cs/mod.rs

@@ -398,7 +398,7 @@ impl CsCodeOracle {
             FfiType::RustBuffer(_) => "RustBuffer".to_string(),
             FfiType::ForeignBytes => "ForeignBytes".to_string(),
             FfiType::Callback(_) => "IntPtr".to_string(),
-            FfiType::Reference(typ) => format!("ref {}", self.ffi_type_label(typ, prefix_struct)),
+            FfiType::Reference(typ) => format!("IntPtr /*{}*/", self.ffi_type_label(typ, prefix_struct)),
             FfiType::RustCallStatus => "UniffiRustCallStatus".to_string(),
             FfiType::Struct(name) => {
                 if prefix_struct {
@@ -410,4 +410,4 @@ impl CsCodeOracle {
             FfiType::VoidPointer => "IntPtr".to_string(),
         }
     }
-}
+}

bindgen/templates/CallbackInterfaceImpl.cs

@@ -22,7 +22,10 @@ class {{ callback_impl_name }} {
 
             {%- match meth.return_type() %}
             {%- when Some with (return_type) %}
-            @uniffiOutReturn = {{ return_type|ffi_converter_name }}.INSTANCE.Lower(result);
+            unsafe {
+                {%- let return_ffi_type = return_type|ffi_type %}
+                *({{ return_ffi_type|ffi_type_name }}*)uniffiOutReturn = {{ return_type|ffi_converter_name }}.INSTANCE.Lower(result);
+            }
             {%- when None %}
             {%- endmatch %}
 
@@ -109,8 +112,10 @@ class {{ callback_impl_name }} {
             }, cts.Token);
 
             var foreignHandle = _UniFFIAsync._foreign_futures_map.Insert(cts);
-            @uniffiOutReturn.@handle = foreignHandle;
-            @uniffiOutReturn.@free = Marshal.GetFunctionPointerForDelegate(_UniFFIAsync.UniffiForeignFutureFreeCallback.callback);
+            unsafe {
+                (*(_UniFFILib.UniffiForeignFuture*)uniffiOutReturn).handle = foreignHandle;
+                (*(_UniFFILib.UniffiForeignFuture*)uniffiOutReturn).free = Marshal.GetFunctionPointerForDelegate(_UniFFIAsync.UniffiForeignFutureFreeCallback.callback);;
+            }
             {%- endif %}
         } else {
             throw new InternalException($"No callback in handlemap '{handle}'");
@@ -128,16 +133,17 @@ static void UniffiFree(ulong @handle) {
     {%- endfor %}
     static _UniFFILib.UniffiCallbackInterfaceFree _callback_interface_free = new _UniFFILib.UniffiCallbackInterfaceFree(UniffiFree);
 
-    public static _UniFFILib.{{ vtable|ffi_type_name }} _vtable = new _UniFFILib.{{ vtable|ffi_type_name }} {
-        {%- for (ffi_callback, meth) in vtable_methods.iter() %}
-        {%- let fn_type = format!("_UniFFILib.{}Method", callback_impl_name) %}
-        {{ meth.name()|var_name() }} = Marshal.GetFunctionPointerForDelegate(_m{{ loop.index0 }}),
-        {%- endfor %}
-        @uniffiFree = Marshal.GetFunctionPointerForDelegate(_callback_interface_free)
-    };
-
     public static void Register() {
-        _UniFFILib.{{ ffi_init_callback.name() }}(ref {{ callback_impl_name }}._vtable);
+        _UniFFILib.{{ vtable|ffi_type_name }} _vtable = new _UniFFILib.{{ vtable|ffi_type_name }} {
+            {%- for (ffi_callback, meth) in vtable_methods.iter() %}
+            {%- let fn_type = format!("_UniFFILib.{}Method", callback_impl_name) %}
+            {{ meth.name()|var_name() }} = Marshal.GetFunctionPointerForDelegate(_m{{ loop.index0 }}),
+            {%- endfor %}
+            @uniffiFree = Marshal.GetFunctionPointerForDelegate(_callback_interface_free)
+        };
+
+        // Pin vtable to ensure GC does not move the vtable across the heap
+        _UniFFILib.{{ ffi_init_callback.name() }}(GCHandle.Alloc(_vtable, GCHandleType.Pinned).AddrOfPinnedObject());
     }
 }