This allows CStr constants to be defined easily on Rust 1.63.0, while
checking that there are no embedded NULs. c"" literals were only
stabilized in Rust 1.77.0.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
rust/hw/char/pl011/src/device.rs | 3 +-
rust/hw/char/pl011/src/device_class.rs | 10 +++--
rust/hw/char/pl011/src/lib.rs | 4 +-
rust/qemu-api/meson.build | 1 +
rust/qemu-api/src/c_str.rs | 52 ++++++++++++++++++++++++++
rust/qemu-api/src/lib.rs | 1 +
rust/qemu-api/src/tests.rs | 8 ++--
7 files changed, 70 insertions(+), 9 deletions(-)
create mode 100644 rust/qemu-api/src/c_str.rs
diff --git a/rust/hw/char/pl011/src/device.rs b/rust/hw/char/pl011/src/device.rs
index cd4c01c2336..55d933ee5e9 100644
--- a/rust/hw/char/pl011/src/device.rs
+++ b/rust/hw/char/pl011/src/device.rs
@@ -11,6 +11,7 @@
use qemu_api::{
bindings::{self, *},
+ c_str,
definitions::ObjectImpl,
};
@@ -99,7 +100,7 @@ impl qemu_api::definitions::Class for PL011Class {
}
#[used]
-pub static CLK_NAME: &CStr = c"clk";
+pub static CLK_NAME: &CStr = c_str!("clk");
impl PL011State {
/// Initializes a pre-allocated, unitialized instance of `PL011State`.
diff --git a/rust/hw/char/pl011/src/device_class.rs b/rust/hw/char/pl011/src/device_class.rs
index b7ab31af02d..a3d1b1e929a 100644
--- a/rust/hw/char/pl011/src/device_class.rs
+++ b/rust/hw/char/pl011/src/device_class.rs
@@ -4,7 +4,11 @@
use core::ptr::NonNull;
-use qemu_api::{bindings::*, definitions::ObjectImpl};
+use qemu_api::{
+ bindings::*,
+ c_str,
+ definitions::ObjectImpl
+};
use crate::device::PL011State;
@@ -18,14 +22,14 @@
qemu_api::declare_properties! {
PL011_PROPERTIES,
qemu_api::define_property!(
- c"chardev",
+ c_str!("chardev"),
PL011State,
char_backend,
unsafe { &qdev_prop_chr },
CharBackend
),
qemu_api::define_property!(
- c"migrate-clk",
+ c_str!("migrate-clk"),
PL011State,
migrate_clock,
unsafe { &qdev_prop_bool },
diff --git a/rust/hw/char/pl011/src/lib.rs b/rust/hw/char/pl011/src/lib.rs
index 2b157868b0f..0a598e5629d 100644
--- a/rust/hw/char/pl011/src/lib.rs
+++ b/rust/hw/char/pl011/src/lib.rs
@@ -41,11 +41,13 @@
extern crate bilge_impl;
extern crate qemu_api;
+use qemu_api::c_str;
+
pub mod device;
pub mod device_class;
pub mod memory_ops;
-pub const TYPE_PL011: &::std::ffi::CStr = c"pl011";
+pub const TYPE_PL011: &::std::ffi::CStr = c_str!("pl011");
/// Offset of each register from the base memory address of the device.
///
diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 436e2f1e836..b55931c6490 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -3,6 +3,7 @@ _qemu_api_rs = static_library(
structured_sources(
[
'src/lib.rs',
+ 'src/c_str.rs',
'src/definitions.rs',
'src/device_class.rs',
'src/tests.rs',
diff --git a/rust/qemu-api/src/c_str.rs b/rust/qemu-api/src/c_str.rs
new file mode 100644
index 00000000000..0286dade306
--- /dev/null
+++ b/rust/qemu-api/src/c_str.rs
@@ -0,0 +1,52 @@
+// Copyright 2024 Red Hat, Inc.
+// Author(s): Paolo Bonzini <pbonzini@redhat.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#[macro_export]
+/// Given a string constant _without_ embedded or trailing NULs, return
+/// a CStr.
+///
+/// Needed for compatibility with Rust <1.77.
+macro_rules! c_str {
+ ($str:expr) => {{
+ const STRING: &str = concat!($str, "\0");
+ const BYTES: &[u8] = STRING.as_bytes();
+
+ // "for" is not allowed in const context... oh well,
+ // everybody loves some lisp. This could be turned into
+ // a procedural macro if this is a problem; alternatively
+ // Rust 1.72 makes CStr::from_bytes_with_nul a const function.
+ const fn f(b: &[u8], i: usize) {
+ if i == BYTES.len() - 1 {}
+ else if BYTES[i] == 0 {
+ panic!("c_str argument contains NUL")
+ } else {
+ f(b, i + 1)
+ }
+ }
+ f(BYTES, 0);
+
+ // SAFETY: absence of NULs apart from the final byte was checked above
+ unsafe { std::ffi::CStr::from_bytes_with_nul_unchecked(BYTES) }
+ }};
+}
+
+#[cfg(test)]
+mod tests {
+ use std::ffi::CStr;
+ use crate::c_str;
+
+ #[test]
+ fn test_cstr_macro() {
+ let good = c_str!("🦀");
+ let good_bytes = b"\xf0\x9f\xa6\x80\0";
+ assert_eq!(good.to_bytes_with_nul(), good_bytes);
+ }
+
+ #[test]
+ fn test_cstr_macro_const() {
+ const GOOD: &CStr = c_str!("🦀");
+ const GOOD_BYTES: &[u8] = b"\xf0\x9f\xa6\x80\0";
+ assert_eq!(GOOD.to_bytes_with_nul(), GOOD_BYTES);
+ }
+}
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index c2f60ac4727..9b2483fbfa3 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -27,6 +27,7 @@ unsafe impl Sync for bindings::Property {}
unsafe impl Sync for bindings::TypeInfo {}
unsafe impl Sync for bindings::VMStateDescription {}
+pub mod c_str;
pub mod definitions;
pub mod device_class;
diff --git a/rust/qemu-api/src/tests.rs b/rust/qemu-api/src/tests.rs
index f0cd4d5d716..d34b8d24187 100644
--- a/rust/qemu-api/src/tests.rs
+++ b/rust/qemu-api/src/tests.rs
@@ -3,7 +3,7 @@
// SPDX-License-Identifier: GPL-2.0-or-later
use crate::{
- bindings::*, declare_properties, define_property, device_class_init, vm_state_description,
+ bindings::*, c_str, declare_properties, define_property, device_class_init, vm_state_description,
};
#[test]
@@ -11,7 +11,7 @@ fn test_device_decl_macros() {
// Test that macros can compile.
vm_state_description! {
VMSTATE,
- name: c"name",
+ name: c_str!("name"),
unmigratable: true,
}
@@ -24,14 +24,14 @@ pub struct DummyState {
declare_properties! {
DUMMY_PROPERTIES,
define_property!(
- c"chardev",
+ c_str!("chardev"),
DummyState,
char_backend,
unsafe { &qdev_prop_chr },
CharBackend
),
define_property!(
- c"migrate-clk",
+ c_str!("migrate-clk"),
DummyState,
migrate_clock,
unsafe { &qdev_prop_bool },
--
2.46.2