Merge pull request #143 from NordSecurity/kristupas/vtable-lifetime

Fix callback vtable lifetime

Author: Jauler

bindgen/src/gen_cs/mod.rs

@@ -393,9 +393,9 @@ 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::MutReference(typ) => {
-                format!("ref {}", self.ffi_type_label(typ, prefix_struct))
+                format!("IntPtr /*{}*/", self.ffi_type_label(typ, prefix_struct))
             }
             FfiType::RustCallStatus => "UniffiRustCallStatus".to_string(),
             FfiType::Struct(name) => {

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());
     }
 }