[PATCH 1/2] rust: Add antoher variant for impl_vmstate_struct! macro

[Martin Kletzander <mkletzan@redhat.com>]

From: Martin Kletzander <mkletzan@redhat.com>

In some cases (e.g. in vmstate_tests.rs) the second argument to
impl_vmstate_struct! is actually an existing struct which is then
copied (since VMStateDescription implements Copy) when saved into the
static VMSD using .get().  That is not a problem because it is part of
the data segment and the pointers are not being free'd since they point
to static data.  But it is a problem when tests rely on comparing the
VMState descriptions as pointers rather than contents.  And it also
wastes space, more or less.

Introduce second variant of the macro which can, instead of the
expression, take an identifier or what looks like a reference.  This
second variant is added before the current variant so that it has
preference, and only references the existing static data from it.

This way tests are fixed and space is saved.

And now that the VMStateDescription checking is fixed we can also check
for the right value in test_vmstate_struct_varray_uint8_wrapper().

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
---
I'm not sure whether this is caused by different utility on my system or bash
version or whatever, but without this patch these three tests fail for me and
this patch fixes it.

 rust/qemu-api/src/vmstate.rs         | 11 +++++++++++
 rust/qemu-api/tests/vmstate_tests.rs |  1 +
 2 files changed, 12 insertions(+)

diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs
index b5c6b764fbba..716e52afe740 100644
--- a/rust/qemu-api/src/vmstate.rs
+++ b/rust/qemu-api/src/vmstate.rs
@@ -449,6 +449,17 @@ macro_rules! vmstate_validate {
 /// description of the struct.
 #[macro_export]
 macro_rules! impl_vmstate_struct {
+    ($type:ty, $(&)?$vmsd:ident) => {
+        unsafe impl $crate::vmstate::VMState for $type {
+            const BASE: $crate::bindings::VMStateField =
+                $crate::bindings::VMStateField {
+                    vmsd: $vmsd.as_ref(),
+                    size: ::core::mem::size_of::<$type>(),
+                    flags: $crate::bindings::VMStateFlags::VMS_STRUCT,
+                    ..$crate::zeroable::Zeroable::ZERO
+                };
+        }
+    };
     ($type:ty, $vmsd:expr) => {
         unsafe impl $crate::vmstate::VMState for $type {
             const BASE: $crate::bindings::VMStateField = {
diff --git a/rust/qemu-api/tests/vmstate_tests.rs b/rust/qemu-api/tests/vmstate_tests.rs
index 2c0670ba0eed..7d3180e6c2ea 100644
--- a/rust/qemu-api/tests/vmstate_tests.rs
+++ b/rust/qemu-api/tests/vmstate_tests.rs
@@ -320,6 +320,7 @@ fn test_vmstate_struct_varray_uint8_wrapper() {
         b"arr_a_wrap\0"
     );
     assert_eq!(foo_fields[5].num_offset, 228);
+    assert_eq!(foo_fields[5].vmsd, VMSTATE_FOOA.as_ref());
     assert!(unsafe { foo_fields[5].field_exists.unwrap()(foo_b_p, 0) });
 
     // The last VMStateField in VMSTATE_FOOB.
-- 
2.50.1