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// 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 == b.len() - 1 {
} else if b[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);
}
}
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