Rollup merge of rust-lang#143595 - fee1-dead-contrib:push-sylpykzkmynr, r=RalfJung,fee1-dead

add `const_make_global`; err for `const_allocate` ptrs if didn't call

Implements as discussed on Zulip: [#t-compiler/const-eval > const heap](https://rust-lang.zulipchat.com/#narrow/channel/146212-t-compiler.2Fconst-eval/topic/const.20heap/with/527125421)

r? ```@rust-lang/wg-const-eval```

Fixes rust-lang#129233

Author: fmease

alloc/src/boxed/thin.rs

@@ -5,7 +5,7 @@
 use core::error::Error;
 use core::fmt::{self, Debug, Display, Formatter};
 #[cfg(not(no_global_oom_handling))]
-use core::intrinsics::const_allocate;
+use core::intrinsics::{const_allocate, const_make_global};
 use core::marker::PhantomData;
 #[cfg(not(no_global_oom_handling))]
 use core::marker::Unsize;
@@ -340,9 +340,10 @@ impl<H> WithHeader<H> {
                     alloc.add(metadata_offset).cast();
                 // SAFETY: `*metadata_ptr` is within the allocation.
                 metadata_ptr.write(ptr::metadata::<Dyn>(ptr::dangling::<T>() as *const Dyn));
-
+                // SAFETY: valid heap allocation
+                const_make_global(alloc);
                 // SAFETY: we have just written the metadata.
-                &*(metadata_ptr)
+                &*metadata_ptr
             }
         };
 

core/src/intrinsics/mod.rs

@@ -2533,6 +2533,15 @@ pub const unsafe fn const_deallocate(_ptr: *mut u8, _size: usize, _align: usize)
     // Runtime NOP
 }
 
+#[rustc_const_unstable(feature = "const_heap", issue = "79597")]
+#[rustc_nounwind]
+#[rustc_intrinsic]
+#[miri::intrinsic_fallback_is_spec]
+pub const unsafe fn const_make_global(ptr: *mut u8) -> *const u8 {
+    // const eval overrides this function; at runtime, it is a NOP.
+    ptr
+}
+
 /// Returns whether we should perform contract-checking at runtime.
 ///
 /// This is meant to be similar to the ub_checks intrinsic, in terms