Fixed align on GString for 32-bit support

Co-authored-by: Jan Haller <bromeon@gmail.com>

Author: Esption

godot-core/src/builtin/packed_array.rs

@@ -15,6 +15,10 @@ use sys::{ffi_methods, interface_fn, GodotFfi};
 // FIXME remove dependency on these types
 use sys::{__GdextString, __GdextType};
 
+// TODO(bromeon): ensure and test that all element types can be packed.
+// Many builtin types don't have a #[repr] themselves, but they are used in packed arrays, which assumes certain size and alignment.
+// This is mostly a problem for as_slice(), which reinterprets the FFI representation into the "frontend" type like GString.
+
 /// Defines and implements a single packed array type. This macro is not hygienic and is meant to
 /// be used only in the current module.
 macro_rules! impl_packed_array {

godot-core/src/builtin/string/gstring.rs

@@ -53,7 +53,8 @@ pub type GodotString = GString;
 ///
 /// Godot also provides two separate string classes with slightly different semantics: [`StringName`] and [`NodePath`].
 #[doc(alias = "String")]
-#[repr(C, align(8))]
+// #[repr] is needed on GString itself rather than the opaque field, because PackedStringArray::as_slice() relies on a packed representation.
+#[repr(transparent)]
 pub struct GString {
     opaque: OpaqueString,
 }