[PATCH v3 11/15] rust/vmstate: Add unit test for vmstate_of macro

[Zhao Liu <zhao1.liu@intel.com>]

The vmstate has too many combinations of VMStateFlags and VMStateField.
Currently, the best way to test is to ensure that the Rust vmstate
definition is consistent with the (possibly corresponding) C version.

Add a unit test to cover some patterns accepted by vmstate_of macro,
which correspond to the following C version macros:
 * VMSTATE_U16
 * VMSTATE_UNUSED
 * VMSTATE_VARRAY_UINT16_UNSAFE
 * VMSTATE_VARRAY_MULTIPLY

Note: Because vmstate_info_* are defined in vmstate-types.c, it's
necessary to link libmigration to rust unit tests. In the future,
maybe it's possible to spilt libmigration from rust_qemu_api_objs.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 rust/qemu-api/meson.build            |   5 +-
 rust/qemu-api/tests/tests.rs         |   2 +
 rust/qemu-api/tests/vmstate_tests.rs | 119 +++++++++++++++++++++++++++
 3 files changed, 124 insertions(+), 2 deletions(-)
 create mode 100644 rust/qemu-api/tests/vmstate_tests.rs

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index a3f226ccc2a5..858685ddd4a4 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -58,7 +58,8 @@ rust_qemu_api_objs = static_library(
               libchardev.extract_all_objects(recursive: false),
               libcrypto.extract_all_objects(recursive: false),
               libauthz.extract_all_objects(recursive: false),
-              libio.extract_all_objects(recursive: false)])
+              libio.extract_all_objects(recursive: false),
+              libmigration.extract_all_objects(recursive: false)])
 rust_qemu_api_deps = declare_dependency(
     dependencies: [
       qom_ss.dependencies(),
@@ -71,7 +72,7 @@ rust_qemu_api_deps = declare_dependency(
 test('rust-qemu-api-integration',
     executable(
         'rust-qemu-api-integration',
-        'tests/tests.rs',
+        files('tests/tests.rs', 'tests/vmstate_tests.rs'),
         override_options: ['rust_std=2021', 'build.rust_std=2021'],
         rust_args: ['--test'],
         install: false,
diff --git a/rust/qemu-api/tests/tests.rs b/rust/qemu-api/tests/tests.rs
index 269122e7ec19..99a7aab6fed9 100644
--- a/rust/qemu-api/tests/tests.rs
+++ b/rust/qemu-api/tests/tests.rs
@@ -17,6 +17,8 @@
     zeroable::Zeroable,
 };
 
+mod vmstate_tests;
+
 // Test that macros can compile.
 pub static VMSTATE: VMStateDescription = VMStateDescription {
     name: c_str!("name").as_ptr(),
diff --git a/rust/qemu-api/tests/vmstate_tests.rs b/rust/qemu-api/tests/vmstate_tests.rs
new file mode 100644
index 000000000000..29d4ea774850
--- /dev/null
+++ b/rust/qemu-api/tests/vmstate_tests.rs
@@ -0,0 +1,119 @@
+// Copyright (C) 2025 Intel Corporation.
+// Author(s): Zhao Liu <zhai1.liu@intel.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+use std::{ffi::CStr, mem::size_of, slice};
+
+use qemu_api::{
+    bindings::{vmstate_info_int8, vmstate_info_uint8, vmstate_info_unused_buffer, VMStateFlags},
+    c_str,
+    vmstate::{VMStateDescription, VMStateField},
+    vmstate_fields, vmstate_of, vmstate_unused,
+    zeroable::Zeroable,
+};
+
+const FOO_ARRAY_MAX: usize = 3;
+
+// =========================== Test VMSTATE_FOOA ===========================
+// Test the use cases of the vmstate macro, corresponding to the following C
+// macro variants:
+//   * VMSTATE_FOOA:
+//     - VMSTATE_U16
+//     - VMSTATE_UNUSED
+//     - VMSTATE_VARRAY_UINT16_UNSAFE
+//     - VMSTATE_VARRAY_MULTIPLY
+#[repr(C)]
+#[derive(qemu_api_macros::offsets)]
+struct FooA {
+    arr: [u8; FOO_ARRAY_MAX],
+    num: u16,
+    arr_mul: [i8; FOO_ARRAY_MAX],
+    num_mul: u32,
+    elem: i8,
+}
+
+static VMSTATE_FOOA: VMStateDescription = VMStateDescription {
+    name: c_str!("foo_a").as_ptr(),
+    version_id: 1,
+    minimum_version_id: 1,
+    fields: vmstate_fields! {
+        vmstate_of!(FooA, elem),
+        vmstate_unused!(size_of::<i64>()),
+        vmstate_of!(FooA, arr[0 .. num]).with_version_id(0),
+        vmstate_of!(FooA, arr_mul[0 .. num_mul * 16]),
+    },
+    ..Zeroable::ZERO
+};
+
+#[test]
+fn test_vmstate_macro_fooa() {
+    let foo_fields: &[VMStateField] = unsafe { slice::from_raw_parts(VMSTATE_FOOA.fields, 5) };
+
+    // 1st VMStateField ("elem") in VMSTATE_FOOA (corresponding to VMSTATE_U16)
+    assert_eq!(
+        unsafe { CStr::from_ptr(foo_fields[0].name) }.to_bytes_with_nul(),
+        b"elem\0"
+    );
+    assert_eq!(foo_fields[0].offset, 16);
+    assert_eq!(foo_fields[0].num_offset, 0);
+    assert_eq!(foo_fields[0].info, unsafe { &vmstate_info_int8 });
+    assert_eq!(foo_fields[0].version_id, 0);
+    assert_eq!(foo_fields[0].size, 1);
+    assert_eq!(foo_fields[0].num, 0);
+    assert_eq!(foo_fields[0].flags, VMStateFlags::VMS_SINGLE);
+    assert_eq!(foo_fields[0].vmsd.is_null(), true);
+    assert_eq!(foo_fields[0].field_exists.is_none(), true);
+
+    // 2nd VMStateField ("unused") in VMSTATE_FOOA (corresponding to VMSTATE_UNUSED)
+    assert_eq!(
+        unsafe { CStr::from_ptr(foo_fields[1].name) }.to_bytes_with_nul(),
+        b"unused\0"
+    );
+    assert_eq!(foo_fields[1].offset, 0);
+    assert_eq!(foo_fields[1].num_offset, 0);
+    assert_eq!(foo_fields[1].info, unsafe { &vmstate_info_unused_buffer });
+    assert_eq!(foo_fields[1].version_id, 0);
+    assert_eq!(foo_fields[1].size, 8);
+    assert_eq!(foo_fields[1].num, 0);
+    assert_eq!(foo_fields[1].flags, VMStateFlags::VMS_BUFFER);
+    assert_eq!(foo_fields[1].vmsd.is_null(), true);
+    assert_eq!(foo_fields[1].field_exists.is_none(), true);
+
+    // 3rd VMStateField ("arr") in VMSTATE_FOOA (corresponding to
+    // VMSTATE_VARRAY_UINT16_UNSAFE)
+    assert_eq!(
+        unsafe { CStr::from_ptr(foo_fields[2].name) }.to_bytes_with_nul(),
+        b"arr\0"
+    );
+    assert_eq!(foo_fields[2].offset, 0);
+    assert_eq!(foo_fields[2].num_offset, 4);
+    assert_eq!(foo_fields[2].info, unsafe { &vmstate_info_uint8 });
+    assert_eq!(foo_fields[2].version_id, 0);
+    assert_eq!(foo_fields[2].size, 1);
+    assert_eq!(foo_fields[2].num, 0);
+    assert_eq!(foo_fields[2].flags, VMStateFlags::VMS_VARRAY_UINT16);
+    assert_eq!(foo_fields[2].vmsd.is_null(), true);
+    assert_eq!(foo_fields[2].field_exists.is_none(), true);
+
+    // 4th VMStateField ("arr_mul") in VMSTATE_FOOA (corresponding to
+    // VMSTATE_VARRAY_MULTIPLY)
+    assert_eq!(
+        unsafe { CStr::from_ptr(foo_fields[3].name) }.to_bytes_with_nul(),
+        b"arr_mul\0"
+    );
+    assert_eq!(foo_fields[3].offset, 6);
+    assert_eq!(foo_fields[3].num_offset, 12);
+    assert_eq!(foo_fields[3].info, unsafe { &vmstate_info_int8 });
+    assert_eq!(foo_fields[3].version_id, 0);
+    assert_eq!(foo_fields[3].size, 1);
+    assert_eq!(foo_fields[3].num, 16);
+    assert_eq!(
+        foo_fields[3].flags.0,
+        VMStateFlags::VMS_VARRAY_UINT32.0 | VMStateFlags::VMS_MULTIPLY_ELEMENTS.0
+    );
+    assert_eq!(foo_fields[3].vmsd.is_null(), true);
+    assert_eq!(foo_fields[3].field_exists.is_none(), true);
+
+    // The last VMStateField in VMSTATE_FOOA.
+    assert_eq!(foo_fields[4].flags, VMStateFlags::VMS_END);
+}
-- 
2.34.1