On Wednesday, October 29, 2025, Giuseppe D'Angelo wrote:

Why would they crash? This again has been extensively discussed; the Standard says that you can trivially relocate trivially relocatable polymorphic types, and people working on the arm64e ABI have confirmed that this is perfectly acceptable and implementable.

Oliver works at Apple and he worked on the arm64e compiler, and here's what he said an hour or two ago in this thread:

"For the topic at hand clang currently does not support trivial relocation of polymorphic types - and reports correctly that such are not."

Basically he's saying that the following assertion will always succeed:

static_assert( false == (is_polymorphic_v<T> && is_trivially_relocatable_v<T>) );

On an arm64e computer, if you relocate a polymorphic object, and then invoke a virtual method, the attempt to access the vtable will cause a CPU trap because the vtable pointer will be incorrectly encrypted.

(Not sure if it will be a "CPU trap" but it will crash in some way)