Rollup merge of #129684 - Strophox:miri-pass-pointer-to-ffi, r=RalfJung

Enable Miri to pass pointers through FFI

Following https://github.com/rust-lang/rust/pull/126787, the purpose of this PR is to now enable Miri to execute native calls that make use of pointers.

> <details>
>
> <summary> Simple example </summary>
>
> ```rust
> extern "C" {
>     fn ptr_printer(ptr: *mut i32);
> }
>
> fn main() {
>     let ptr = &mut 42 as *mut i32;
>     unsafe {
>         ptr_printer(ptr);
>     }
> }
> ```
> ```c
> void ptr_printer(int *ptr) {
>   printf("printing pointer dereference from C: %d\n", *ptr);
> }
> ```
> should now show `printing pointer dereference from C: 42`.
>
> </details>

Note that this PR does not yet implement any logic involved in updating Miri's "analysis" state (byte initialization, provenance) upon such a native call.

r? ``@RalfJung``

1 files changed, 1 insertions, 11 deletions

diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs
index 88453245b84..6cfd7be48e6 100644
--- a/compiler/rustc_const_eval/src/interpret/machine.rs
+++ b/compiler/rustc_const_eval/src/interpret/machine.rs
@@ -362,17 +362,7 @@ pub trait Machine<'tcx>: Sized {
         ecx: &InterpCx<'tcx, Self>,
         id: AllocId,
         alloc: &'b Allocation,
-    ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>
-    {
-        // The default implementation does a copy; CTFE machines have a more efficient implementation
-        // based on their particular choice for `Provenance`, `AllocExtra`, and `Bytes`.
-        let kind = Self::GLOBAL_KIND
-            .expect("if GLOBAL_KIND is None, adjust_global_allocation must be overwritten");
-        let alloc = alloc.adjust_from_tcx(&ecx.tcx, |ptr| ecx.global_root_pointer(ptr))?;
-        let extra =
-            Self::init_alloc_extra(ecx, id, MemoryKind::Machine(kind), alloc.size(), alloc.align)?;
-        Ok(Cow::Owned(alloc.with_extra(extra)))
-    }
+    ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::Provenance, Self::AllocExtra, Self::Bytes>>>;
 
     /// Initialize the extra state of an allocation.
     ///