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bevyengine / bevy

A refreshingly simple data-driven game engine built in Rust
https://bevyengine.org
Apache License 2.0
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Fix dynamic linking failures from the `AnimationEventFn` change. #16476

Closed pcwalton closed 2 days ago

pcwalton commented 3 days ago

I'm not sure why, but somehow #[derive(Reflect)] on a tuple struct with a boxed trait object can result in linker errors when dynamic linking is used on Windows using rust-lld:

  = note: rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..reflect..PartialReflect$u20$for$u20$bevy_animation..AnimationEventFn$GT$::reflect_partial_eq::hc4cce1dc55e42e0b␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..from_reflect..FromReflect$u20$for$u20$bevy_animation..AnimationEventFn$GT$::from_reflect::hc2b1d575b8491092␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..tuple_struct..TupleStruct$u20$for$u20$bevy_animation..AnimationEventFn$GT$::clone_dynamic::hab42a4edc8d6b5c2␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..tuple_struct..TupleStruct$u20$for$u20$bevy_animation..AnimationEventFn$GT$::field::h729a3d6dd6a27a43␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..tuple_struct..TupleStruct$u20$for$u20$bevy_animation..AnimationEventFn$GT$::field_mut::hde1c34846d77344b␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..type_registry..GetTypeRegistration$u20$for$u20$bevy_animation..AnimationEventFn$GT$::get_type_registration::hb96eb543e403a132␍
          rust-lld: error: <root>: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..type_registry..GetTypeRegistration$u20$for$u20$bevy_animation..AnimationEventFn$GT$::register_type_dependencies::hcf1a4b69bcfea6ae␍
          rust-lld: error: undefined symbol: bevy_animation::_::_$LT$impl$u20$bevy_reflect..reflect..PartialReflect$u20$for$u20$bevy_animation..AnimationEventFn$GT$::reflect_partial_eq::hc4cce1dc55e42e0b␍

etc.

Adding #[reflect(opaque)] to the Reflect derive fixes the problem, and that's what this patch does. I think that adding #[reflect(opaque)] is harmless, as there's little that reflection allows with a boxed trait object anyhow.

pcwalton commented 3 days ago

This is a regression in #16440.