fix horrible bug that never allocated memory if native-lib was off

Author: Strophox

src/tools/miri/src/machine.rs

@@ -1244,16 +1244,20 @@ impl<'tcx> Machine<'tcx> for MiriMachine<'tcx> {
         // 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");
-        // This closure is special in that it always relies on `take_prepared_alloc_bytes`
-        // to give it some reserved memory space.
+        // This closure is special in that it relies on `take_prepared_alloc_bytes` to give it some
+        // reserved memory space in case Miri needs to handle addresses especially for native calls.
         let alloc = alloc.adjust_from_tcx(&ecx.tcx, |bytes, align| {
-                assert_eq!(alloc.align, align);
-                let kind = Self::GLOBAL_KIND.unwrap().into();
-                let mut alloc_bytes = ecx.take_prepared_alloc_bytes(id, kind)?;
-                assert_eq!(alloc_bytes.len(), bytes.len());
-                // SAFETY: `alloc_bytes` and `bytes` span the same number of bytes.
-                unsafe { alloc_bytes.as_mut_ptr().copy_from(bytes.as_ptr(), bytes.len()) };
-                Ok(alloc_bytes)
+                Ok(if ecx.machine.native_lib.is_some() {
+                    assert_eq!(alloc.align, align);
+                    let kind = Self::GLOBAL_KIND.unwrap().into();
+                    let mut alloc_bytes = ecx.take_prepared_alloc_bytes(id, kind)?;
+                    assert_eq!(alloc_bytes.len(), bytes.len());
+                    // SAFETY: `alloc_bytes` and `bytes` span the same number of bytes.
+                    unsafe { alloc_bytes.as_mut_ptr().copy_from(bytes.as_ptr(), bytes.len()) };
+                    alloc_bytes
+                } else {
+                    MiriAllocBytes::from_bytes(Cow::Borrowed(&*bytes), align)
+                })
             }, 
             |ptr| ecx.global_root_pointer(ptr),
         )?;