Re: [PATCH RESEND v5] rust: str: Use `core::CStr`, remove the custom `CStr` implementation

19 Aug 2024

On 8/19/24 17:36, Michal Rostecki wrote:
...
From: Michal Rostecki vadorovsky@gmail.com
`CStr` became a part of `core` library in Rust 1.75. This change replaces
the custom `CStr` implementation with the one from `core`.
`core::CStr` behaves generally the same as the removed implementation,
with the following differences:

It does not implement `Display`.
It does not provide `from_bytes_with_nul_unchecked_mut` method.
It has `as_ptr()` method instead of `as_char_ptr()`, which also returns
 `*const c_char`.

The first two differences are handled by providing the `CStrExt` trait,
with `display()` and `from_bytes_with_nul_unchecked_mut()` methods.
`display()` returns a `CStrDisplay` wrapper, with a custom `Display`
implementation.
`DerefMut` implementation for `CString` is removed here, as it's not
being used anywhere.
Signed-off-by: Michal Rostecki vadorovsky@gmail.com
rust/kernel/error.rs        |   7 +-
  rust/kernel/kunit.rs        |  18 +-
  rust/kernel/net/phy.rs      |   2 +-
  rust/kernel/prelude.rs      |   4 +-
  rust/kernel/str.rs          | 465 ++++++------------------------------
  rust/kernel/sync/condvar.rs |   5 +-
  rust/kernel/sync/lock.rs    |   6 +-
  rust/kernel/workqueue.rs    |   2 +-
  scripts/rustdoc_test_gen.rs |   4 +-
  9 files changed, 93 insertions(+), 420 deletions(-)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 6f1587a2524e..6a2bb11ac09c 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -4,10 +4,11 @@
  //!
  //! C header: [`include/uapi/asm-generic/errno-base.h`](srctree/include/uapi/asm-generic/errno-base.h)
  
-use crate::{alloc::AllocError, str::CStr};
+use crate::alloc::AllocError;
  
  use alloc::alloc::LayoutError;
  
+use core::ffi::CStr;
  use core::fmt;
  use core::num::TryFromIntError;
  use core::str::Utf8Error;
@@ -151,7 +152,7 @@ pub fn name(&self) -> Option<&'static CStr> {
              None
          } else {
              // SAFETY: The string returned by `errname` is static and `NUL`-terminated.

       Some(unsafe { CStr::from_char_ptr(ptr) })




       Some(unsafe { CStr::from_ptr(ptr) })
    }
}



@@ -173,7 +174,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
              None => f.debug_tuple("Error").field(&-self.0).finish(),
              // SAFETY: These strings are ASCII-only.
              Some(name) => f

           .debug_tuple(unsafe { core::str::from_utf8_unchecked(name) })




           .debug_tuple(unsafe { core::str::from_utf8_unchecked(name.to_bytes()) })
            .finish(),
    }
}



diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 0ba77276ae7e..79a50ab59af0 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -56,13 +56,15 @@ macro_rules! kunit_assert {
                  break 'out;
              }

       static FILE: &'static $crate::str::CStr = $crate::c_str!($file);




       static FILE: &'static core::ffi::CStr = $file;
        static LINE: i32 = core::line!() as i32 - $diff;




       static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));




       static CONDITION: &'static core::ffi::CStr = $crate::c_str!(stringify!($condition));



// SAFETY: FFI call without safety requirements.
              let kunit_test = unsafe { $crate::bindings::kunit_get_current_test() };
              if kunit_test.is_null() {

           use kernel::str::CStrExt;


            // The assertion failed but this task is not running a KUnit test, so we cannot call
            // KUnit, but at least print an error to the kernel log. This may happen if this
            // macro is called from an spawned thread in a test (see



@@ -71,11 +73,13 @@ macro_rules! kunit_assert {
                  //
                  // This mimics KUnit's failed assertion format.
                  $crate::kunit::err(format_args!(

               "    # {}: ASSERTION FAILED at {FILE}:{LINE}\n",


               $name




               "    # {}: ASSERTION FAILED at {}:{LINE}\n",


               $name.display(),


               FILE.display(),
            ));
            $crate::kunit::err(format_args!(




               "    Expected {CONDITION} to be true, but is false\n"




               "    Expected {} to be true, but is false\n",


               CONDITION.display(),
            ));
            $crate::kunit::err(format_args!(
                "    Failure not reported to KUnit since this is a non-KUnit task\n"



@@ -98,12 +102,12 @@ unsafe impl Sync for Location {}
              unsafe impl Sync for UnaryAssert {}
  
              static LOCATION: Location = Location($crate::bindings::kunit_loc {

           file: FILE.as_char_ptr(),




           file: FILE.as_ptr(),
            line: LINE,
        });
        static ASSERTION: UnaryAssert = UnaryAssert($crate::bindings::kunit_unary_assert {
            assert: $crate::bindings::kunit_assert {},




           condition: CONDITION.as_char_ptr(),




           condition: CONDITION.as_ptr(),
            expected_true: true,
        });



diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index fd40b703d224..19f45922ec42 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -502,7 +502,7 @@ unsafe impl Sync for DriverVTable {}
  pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
      // INVARIANT: All the fields of `struct phy_driver` are initialized properly.
      DriverVTable(Opaque::new(bindings::phy_driver {

   name: T::NAME.as_char_ptr().cast_mut(),




   name: T::NAME.as_ptr().cast_mut(),
    flags: T::FLAGS,
    phy_id: T::PHY_DEVICE_ID.id,
    phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),



diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index b37a0b3180fb..b0969ca78f10 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -12,7 +12,7 @@
  //! ```
  
  #[doc(no_inline)]
-pub use core::pin::Pin;
+pub use core::{ffi::CStr, pin::Pin};
  
  pub use crate::alloc::{box_ext::BoxExt, flags::*, vec_ext::VecExt};
  
@@ -35,7 +35,7 @@
  
  pub use super::error::{code::*, Error, Result};
  
-pub use super::{str::CStr, ThisModule};
+pub use super::ThisModule;
  
  pub use super::init::{InPlaceInit, Init, PinInit};
  
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index bb8d4f41475b..97a298a44b96 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -4,8 +4,9 @@
  
  use crate::alloc::{flags::*, vec_ext::VecExt, AllocError};
  use alloc::vec::Vec;
+use core::ffi::CStr;
  use core::fmt::{self, Write};
-use core::ops::{self, Deref, DerefMut, Index};
+use core::ops::Deref;
  
  use crate::error::{code::*, Error};
  
@@ -41,11 +42,11 @@ impl fmt::Display for BStr {
      /// # use kernel::{fmt, b_str, str::{BStr, CString}};
      /// let ascii = b_str!("Hello, BStr!");
      /// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();

/// assert_eq!(s.as_bytes(), "Hello, BStr!".as_bytes());


/// assert_eq!(s.to_bytes(), "Hello, BStr!".as_bytes());
 ///
 /// let non_ascii = b_str!("🦀");
 /// let s = CString::try_from_fmt(fmt!("{}", non_ascii)).unwrap();


/// assert_eq!(s.as_bytes(), "\xf0\x9f\xa6\x80".as_bytes());


/// assert_eq!(s.to_bytes(), "\xf0\x9f\xa6\x80".as_bytes());
 /// ```
 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     for &b in &self.0 {

@@ -72,11 +73,11 @@ impl fmt::Debug for BStr {
      /// // Embedded double quotes are escaped.
      /// let ascii = b_str!("Hello, "BStr"!");
      /// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();

/// assert_eq!(s.as_bytes(), ""Hello, \"BStr\"!"".as_bytes());


/// assert_eq!(s.to_bytes(), ""Hello, \"BStr\"!"".as_bytes());
 ///
 /// let non_ascii = b_str!("😺");
 /// let s = CString::try_from_fmt(fmt!("{:?}", non_ascii)).unwrap();


/// assert_eq!(s.as_bytes(), ""\xf0\x9f\x98\xba"".as_bytes());


/// assert_eq!(s.to_bytes(), ""\xf0\x9f\x98\xba"".as_bytes());
 /// ```
 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     f.write_char('"')?;

@@ -128,271 +129,29 @@ macro_rules! b_str {
      }};
  }
  
-/// Possible errors when using conversion functions in [`CStr`].
-#[derive(Debug, Clone, Copy)]
-pub enum CStrConvertError {

/// Supplied bytes contain an interior `NUL`.
InteriorNul,

+/// Wrapper around [`CStr`] which implements [`Display`](core::fmt::Display).
+pub struct CStrDisplay<'a>(&'a CStr);

/// Supplied bytes are not terminated by `NUL`.
NotNulTerminated,

-}



-impl From<CStrConvertError> for Error {

#[inline]
fn from(_: CStrConvertError) -> Error {
   EINVAL


}

-}



-/// A string that is guaranteed to have exactly one `NUL` byte, which is at the
-/// end.
-///
-/// Used for interoperability with kernel APIs that take C strings.
-#[repr(transparent)]
-pub struct CStr([u8]);



-impl CStr {

/// Returns the length of this string excluding `NUL`.
#[inline]
pub const fn len(&self) -> usize {
   self.len_with_nul() - 1


}

/// Returns the length of this string with `NUL`.
#[inline]
pub const fn len_with_nul(&self) -> usize {
   // SAFETY: This is one of the invariant of `CStr`.


   // We add a `unreachable_unchecked` here to hint the optimizer that


   // the value returned from this function is non-zero.


   if self.0.is_empty() {


       unsafe { core::hint::unreachable_unchecked() };


   }


   self.0.len()


}

/// Returns `true` if the string only includes `NUL`.
#[inline]
pub const fn is_empty(&self) -> bool {
   self.len() == 0


}

/// Wraps a raw C string pointer.
///
/// # Safety
///
/// `ptr` must be a valid pointer to a `NUL`-terminated C string, and it must
/// last at least `'a`. When `CStr` is alive, the memory pointed by `ptr`
/// must not be mutated.
#[inline]
pub unsafe fn from_char_ptr<'a>(ptr: *const core::ffi::c_char) -> &'a Self {
   // SAFETY: The safety precondition guarantees `ptr` is a valid pointer


   // to a `NUL`-terminated C string.


   let len = unsafe { bindings::strlen(ptr) } + 1;


   // SAFETY: Lifetime guaranteed by the safety precondition.


   let bytes = unsafe { core::slice::from_raw_parts(ptr as _, len as _) };


   // SAFETY: As `len` is returned by `strlen`, `bytes` does not contain interior `NUL`.


   // As we have added 1 to `len`, the last byte is known to be `NUL`.


   unsafe { Self::from_bytes_with_nul_unchecked(bytes) }


}

/// Creates a [`CStr`] from a `[u8]`.
///
/// The provided slice must be `NUL`-terminated, does not contain any
/// interior `NUL` bytes.
pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError> {
   if bytes.is_empty() {


       return Err(CStrConvertError::NotNulTerminated);


   }


   if bytes[bytes.len() - 1] != 0 {


       return Err(CStrConvertError::NotNulTerminated);


   }


   let mut i = 0;


   // `i + 1 < bytes.len()` allows LLVM to optimize away bounds checking,


   // while it couldn't optimize away bounds checks for `i < bytes.len() - 1`.


   while i + 1 < bytes.len() {


       if bytes[i] == 0 {


           return Err(CStrConvertError::InteriorNul);


       }


       i += 1;


   }


   // SAFETY: We just checked that all properties hold.


   Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) })


}

/// Creates a [`CStr`] from a `[u8]` without performing any additional
/// checks.
///
/// # Safety
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
#[inline]
pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
   // SAFETY: Properties of `bytes` guaranteed by the safety precondition.


   unsafe { core::mem::transmute(bytes) }


}

/// Creates a mutable [`CStr`] from a `[u8]` without performing any
/// additional checks.
///
/// # Safety
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
#[inline]
pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
   // SAFETY: Properties of `bytes` guaranteed by the safety precondition.


   unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }


}

/// Returns a C pointer to the string.
#[inline]
pub const fn as_char_ptr(&self) -> *const core::ffi::c_char {
   self.0.as_ptr() as _


}

/// Convert the string to a byte slice without the trailing `NUL` byte.
#[inline]
pub fn as_bytes(&self) -> &[u8] {
   &self.0[..self.len()]


}

/// Convert the string to a byte slice containing the trailing `NUL` byte.
#[inline]
pub const fn as_bytes_with_nul(&self) -> &[u8] {
   &self.0


}

/// Yields a [`&str`] slice if the [`CStr`] contains valid UTF-8.
///
/// If the contents of the [`CStr`] are valid UTF-8 data, this
/// function will return the corresponding [`&str`] slice. Otherwise,
/// it will return an error with details of where UTF-8 validation failed.
///
/// # Examples
///
/// ```
/// # use kernel::str::CStr;
/// let cstr = CStr::from_bytes_with_nul(b"foo\0").unwrap();
/// assert_eq!(cstr.to_str(), Ok("foo"));
/// ```
#[inline]
pub fn to_str(&self) -> Result<&str, core::str::Utf8Error> {
   core::str::from_utf8(self.as_bytes())


}

/// Unsafely convert this [`CStr`] into a [`&str`], without checking for
/// valid UTF-8.
///
/// # Safety
///
/// The contents must be valid UTF-8.

+impl fmt::Display for CStrDisplay<'_> {

/// Formats printable ASCII characters, escaping the rest.
 ///
 /// # Examples
 ///
 /// ```


/// # use kernel::c_str;
/// # use kernel::str::CStr;
/// let bar = c_str!("ツ");
/// // SAFETY: String literals are guaranteed to be valid UTF-8
/// // by the Rust compiler.
/// assert_eq!(unsafe { bar.as_str_unchecked() }, "ツ");
/// ```
#[inline]
pub unsafe fn as_str_unchecked(&self) -> &str {
   unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }


}

/// Convert this [`CStr`] into a [`CString`] by allocating memory and
/// copying over the string data.
pub fn to_cstring(&self) -> Result<CString, AllocError> {
   CString::try_from(self)


}

/// Converts this [`CStr`] to its ASCII lower case equivalent in-place.
///
/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
/// but non-ASCII letters are unchanged.
///
/// To return a new lowercased value without modifying the existing one, use
/// [`to_ascii_lowercase()`].
///
/// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
pub fn make_ascii_lowercase(&mut self) {
   // INVARIANT: This doesn't introduce or remove NUL bytes in the C


   // string.


   self.0.make_ascii_lowercase();


}

/// Converts this [`CStr`] to its ASCII upper case equivalent in-place.
///
/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
/// but non-ASCII letters are unchanged.
///
/// To return a new uppercased value without modifying the existing one, use
/// [`to_ascii_uppercase()`].
///
/// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
pub fn make_ascii_uppercase(&mut self) {
   // INVARIANT: This doesn't introduce or remove NUL bytes in the C


   // string.


   self.0.make_ascii_uppercase();


}

/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII lower case equivalent.
///
/// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
/// but non-ASCII letters are unchanged.
///
/// To lowercase the value in-place, use [`make_ascii_lowercase`].
///
/// [`make_ascii_lowercase`]: str::make_ascii_lowercase
pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
   let mut s = self.to_cstring()?;



   s.make_ascii_lowercase();



   Ok(s)


}

/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII upper case equivalent.
///
/// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
/// but non-ASCII letters are unchanged.
///
/// To uppercase the value in-place, use [`make_ascii_uppercase`].
///
/// [`make_ascii_uppercase`]: str::make_ascii_uppercase
pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
   let mut s = self.to_cstring()?;



   s.make_ascii_uppercase();



   Ok(s)


}

-}



-impl fmt::Display for CStr {

/// Formats printable ASCII characters, escaping the rest.
///
/// ```


/// # use core::ffi::CStr;
 /// # use kernel::c_str;
 /// # use kernel::fmt;


/// # use kernel::str::CStr;
/// # use kernel::str::CString;
/// let penguin = c_str!("🐧");
/// let s = CString::try_from_fmt(fmt!("{}", penguin)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "\xf0\x9f\x90\xa7\0".as_bytes());
///
/// let ascii = c_str!("so "cool"");
/// let s = CString::try_from_fmt(fmt!("{}", ascii)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), "so "cool"\0".as_bytes());


/// # use kernel::str::{CStrExt, CString};
/// let penguin = c"🐧";
/// let s = CString::try_from_fmt(fmt!("{}", penguin.display())).unwrap();
/// assert_eq!(s.to_bytes_with_nul(), "\xf0\x9f\x90\xa7\0".as_bytes());
///
/// let ascii = c"so "cool"";
/// let s = CString::try_from_fmt(fmt!("{}", ascii.display())).unwrap();
/// assert_eq!(s.to_bytes_with_nul(), "so "cool"\0".as_bytes());
 /// ```
 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {


   for &c in self.as_bytes() {




   for &c in self.0.to_bytes() {
        if (0x20..0x7f).contains(&c) {
            // Printable character.
            f.write_char(c as char)?;



@@ -404,116 +163,70 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
      }
  }
  
-impl fmt::Debug for CStr {

/// Formats printable ASCII characters with a double quote on either end, escaping the rest.

+/// Extensions to [`CStr`].
+pub trait CStrExt {

/// Returns an object that implements [`Display`](core::fmt::Display) for
/// safely printing a [`CStr`] that may contain non-ASCII data, which are
/// escaped.
///
/// # Examples
 ///
 /// ```
/// # use core::ffi::CStr;
 /// # use kernel::c_str;
 /// # use kernel::fmt;


/// # use kernel::str::CStr;
/// # use kernel::str::CString;
/// let penguin = c_str!("🐧");
/// let s = CString::try_from_fmt(fmt!("{:?}", penguin)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), ""\xf0\x9f\x90\xa7"\0".as_bytes());
///
/// // Embedded double quotes are escaped.
/// let ascii = c_str!("so "cool"");
/// let s = CString::try_from_fmt(fmt!("{:?}", ascii)).unwrap();
/// assert_eq!(s.as_bytes_with_nul(), ""so \"cool\""\0".as_bytes());


/// # use kernel::str::{CStrExt, CString};
/// let penguin = c"🐧";
/// let s = CString::try_from_fmt(fmt!("{}", penguin.display())).unwrap();
/// assert_eq!(s.to_bytes_with_nul(), "\xf0\x9f\x90\xa7\0".as_bytes());
///
/// let ascii = c"so "cool"";
/// let s = CString::try_from_fmt(fmt!("{}", ascii.display())).unwrap();
/// assert_eq!(s.to_bytes_with_nul(), "so "cool"\0".as_bytes());
 /// ```


fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
   f.write_str("\"")?;


   for &c in self.as_bytes() {


       match c {


           // Printable characters.


           b'\"' => f.write_str("\\\"")?,


           0x20..=0x7e => f.write_char(c as char)?,


           _ => write!(f, "\\x{:02x}", c)?,


       }


   }


   f.write_str("\"")


}

-}



-impl AsRef<BStr> for CStr {

#[inline]
fn as_ref(&self) -> &BStr {
   BStr::from_bytes(self.as_bytes())


}

-}



-impl Deref for CStr {

type Target = BStr;

#[inline]
fn deref(&self) -> &Self::Target {
   self.as_ref()


}

-}



-impl Index<ops::RangeFrom<usize>> for CStr {

type Output = CStr;


fn display(&self) -> CStrDisplay<'_>;


#[inline]
fn index(&self, index: ops::RangeFrom<usize>) -> &Self::Output {
   // Delegate bounds checking to slice.


   // Assign to _ to mute clippy's unnecessary operation warning.


   let _ = &self.as_bytes()[index.start..];


   // SAFETY: We just checked the bounds.


   unsafe { Self::from_bytes_with_nul_unchecked(&self.0[index.start..]) }


}


/// Creates a mutable [`CStr`] from a `[u8]` without performing any
/// additional checks.
///
/// # Safety
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self;
}

-impl Indexops::RangeFull for CStr {

type Output = CStr;

#[inline]
fn index(&self, _index: ops::RangeFull) -> &Self::Output {
   self



+impl CStrExt for CStr {

fn display(&self) -> CStrDisplay<'_> {
   CStrDisplay(self)
}



-}
  
-mod private {

use core::ops;

// Marker trait for index types that can be forward to `BStr`.
pub trait CStrIndex {}

impl CStrIndex for usize {}
impl CStrIndex for ops::Range<usize> {}
impl CStrIndex for ops::RangeInclusive<usize> {}
impl CStrIndex for ops::RangeToInclusive<usize> {}

-}



-impl<Idx> Index<Idx> for CStr
-where

Idx: private::CStrIndex,
BStr: Index<Idx>,

-{

type Output = <BStr as Index<Idx>>::Output;

#[inline]
fn index(&self, index: Idx) -> &Self::Output {
   &self.as_ref()[index]




unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self {
   // SAFETY: Properties of `bytes` guaranteed by the safety precondition.


   unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
}

}

/// Creates a new [`CStr`] from a string literal.
  ///
-/// The string literal should not contain any `NUL` bytes.
+/// This macro is not needed when C-string literals (`c"hello"` syntax) can be
+/// used directly, but can be used when a C-string version of a standard string
+/// literal is required (often when working with macros).
+///
+/// The string should not contain any `NUL` bytes.
  ///
  /// # Examples
  ///
  /// ```
+/// # use core::ffi::CStr;
  /// # use kernel::c_str;
-/// # use kernel::str::CStr;
-/// const MY_CSTR: &CStr = c_str!("My awesome CStr!");
+/// const MY_CSTR: &CStr = c_str!(stringify!(5));
  /// ```
  #[macro_export]
  macro_rules! c_str {
      ($str:expr) => {{
          const S: &str = concat!($str, "\0");

   const C: &$crate::str::CStr = match $crate::str::CStr::from_bytes_with_nul(S.as_bytes()) {




   const C: &core::ffi::CStr = match core::ffi::CStr::from_bytes_with_nul(S.as_bytes()) {
        Ok(v) => v,
        Err(_) => panic!("string contains interior NUL"),
    };



@@ -540,40 +253,16 @@ mod tests {
          \xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\
          \xf0\xf1\xf2\xf3\xf4\xf5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff";

#[test]
fn test_cstr_to_str() {
   let good_bytes = b"\xf0\x9f\xa6\x80\0";


   let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();


   let checked_str = checked_cstr.to_str().unwrap();


   assert_eq!(checked_str, "🦀");


}

#[test]
#[should_panic]
fn test_cstr_to_str_panic() {
   let bad_bytes = b"\xc3\x28\0";


   let checked_cstr = CStr::from_bytes_with_nul(bad_bytes).unwrap();


   checked_cstr.to_str().unwrap();


}

#[test]
fn test_cstr_as_str_unchecked() {
   let good_bytes = b"\xf0\x9f\x90\xA7\0";


   let checked_cstr = CStr::from_bytes_with_nul(good_bytes).unwrap();


   let unchecked_str = unsafe { checked_cstr.as_str_unchecked() };


   assert_eq!(unchecked_str, "🐧");


}
#[test]
fn test_cstr_display() {
    let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();


   assert_eq!(format!("{}", hello_world), "hello, world!");




   assert_eq!(format!("{}", hello_world.display()), "hello, world!");
    let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();




   assert_eq!(format!("{}", non_printables), "\\x01\\x09\\x0a");




   assert_eq!(format!("{}", non_printables.display()), "\\x01\\x09\\x0a");
    let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();




   assert_eq!(format!("{}", non_ascii), "d\\xe9j\\xe0 vu");




   assert_eq!(format!("{}", non_ascii.display()), "d\\xe9j\\xe0 vu");
    let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();




   assert_eq!(format!("{}", good_bytes), "\\xf0\\x9f\\xa6\\x80");




   assert_eq!(format!("{}", good_bytes.display()), "\\xf0\\x9f\\xa6\\x80");
}



#[test]
@@ -584,19 +273,7 @@ fn test_cstr_display_all_bytes() {
              bytes[i as usize] = i.wrapping_add(1);
          }
          let cstr = CStr::from_bytes_with_nul(&bytes).unwrap();

   assert_eq!(format!("{}", cstr), ALL_ASCII_CHARS);


}

#[test]
fn test_cstr_debug() {
   let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0").unwrap();


   assert_eq!(format!("{:?}", hello_world), "\"hello, world!\"");


   let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0").unwrap();


   assert_eq!(format!("{:?}", non_printables), "\"\\x01\\x09\\x0a\"");


   let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0").unwrap();


   assert_eq!(format!("{:?}", non_ascii), "\"d\\xe9j\\xe0 vu\"");


   let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0").unwrap();


   assert_eq!(format!("{:?}", good_bytes), "\"\\xf0\\x9f\\xa6\\x80\"");




   assert_eq!(format!("{}", cstr.display()), ALL_ASCII_CHARS);
}



#[test]
@@ -779,11 +456,11 @@ fn write_str(&mut self, s: &str) -> fmt::Result {
  /// use kernel::{str::CString, fmt};
  ///
  /// let s = CString::try_from_fmt(fmt!("{}{}{}", "abc", 10, 20)).unwrap();
-/// assert_eq!(s.as_bytes_with_nul(), "abc1020\0".as_bytes());
+/// assert_eq!(s.to_bytes_with_nul(), "abc1020\0".as_bytes());
  ///
  /// let tmp = "testing";
  /// let s = CString::try_from_fmt(fmt!("{tmp}{}", 123)).unwrap();
-/// assert_eq!(s.as_bytes_with_nul(), "testing123\0".as_bytes());
+/// assert_eq!(s.to_bytes_with_nul(), "testing123\0".as_bytes());
  ///
  /// // This fails because it has an embedded `NUL` byte.
  /// let s = CString::try_from_fmt(fmt!("a\0b{}", 123));
@@ -838,21 +515,13 @@ fn deref(&self) -> &Self::Target {
      }
  }
  
-impl DerefMut for CString {

fn deref_mut(&mut self) -> &mut Self::Target {
   // SAFETY: A `CString` is always NUL-terminated and contains no other


   // NUL bytes.


   unsafe { CStr::from_bytes_with_nul_unchecked_mut(self.buf.as_mut_slice()) }


}

-}

impl<'a> TryFrom<&'a CStr> for CString {
    type Error = AllocError;

fn try_from(cstr: &'a CStr) -> Result<CString, AllocError> {
          let mut buf = Vec::new();

   <Vec<_> as VecExt<_>>::extend_from_slice(&mut buf, cstr.as_bytes_with_nul(), GFP_KERNEL)




   <Vec<_> as VecExt<_>>::extend_from_slice(&mut buf, cstr.to_bytes_with_nul(), GFP_KERNEL)
        .map_err(|_| AllocError)?;



// INVARIANT: The `CStr` and `CString` types have the same invariants for
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 2b306afbe56d..16d1a1cb8d00 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -9,12 +9,11 @@
  use crate::{
      init::PinInit,
      pin_init,

str::CStr,
 task::{MAX_SCHEDULE_TIMEOUT, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE},
 time::Jiffies,
 types::Opaque,
};

-use core::ffi::{c_int, c_long};
+use core::ffi::{c_int, c_long, CStr};
  use core::marker::PhantomPinned;
  use core::ptr;
  use macros::pin_data;
@@ -108,7 +107,7 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
              // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
              // static lifetimes so they live indefinitely.
              wait_queue_head <- Opaque::ffi_init(|slot| unsafe {

           bindings::__init_waitqueue_head(slot, name.as_char_ptr(), key.as_ptr())




           bindings::__init_waitqueue_head(slot, name.as_ptr(), key.as_ptr())
        }),
    })
}



diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index f6c34ca4d819..318ecb5a5916 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -6,8 +6,8 @@
  //! spinlocks, raw spinlocks) to be provided with minimal effort.
  
  use super::LockClassKey;
-use crate::{init::PinInit, pin_init, str::CStr, types::Opaque, types::ScopeGuard};
-use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
+use crate::{init::PinInit, pin_init, types::Opaque, types::ScopeGuard};
+use core::{cell::UnsafeCell, ffi::CStr, marker::PhantomData, marker::PhantomPinned};
  use macros::pin_data;
  
  pub mod mutex;
@@ -113,7 +113,7 @@ pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinIni
              // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
              // static lifetimes so they live indefinitely.
              state <- Opaque::ffi_init(|slot| unsafe {

           B::init(slot, name.as_char_ptr(), key.as_ptr())




           B::init(slot, name.as_ptr(), key.as_ptr())
        }),
    })
}



diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 553a5cba2adc..a6418873e82e 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -380,7 +380,7 @@ pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self
                          slot,
                          Some(T::Pointer::run),
                          false,

                   name.as_char_ptr(),




                   name.as_ptr(),
                    key.as_ptr(),
                )
            }



diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index 5ebd42ae4a3f..339991ee6885 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -172,7 +172,7 @@ pub extern "C" fn {kunit_name}(__kunit_test: *mut kernel::bindings::kunit) {{
      #[allow(unused)]
      macro_rules! assert {{
          ($cond:expr $(,)?) => {{{{

       kernel::kunit_assert!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $cond);




       kernel::kunit_assert!(c"{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $cond);
    }}}}
}}



@@ -180,7 +180,7 @@ macro_rules! assert {{
      #[allow(unused)]
      macro_rules! assert_eq {{
          ($left:expr, $right:expr $(,)?) => {{{{

       kernel::kunit_assert_eq!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);




       kernel::kunit_assert_eq!(c"{kunit_name}", c"{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);
    }}}}
}}



I forgot to include the version history before sending the patch, sorry.
v1 -> v2:
- Do not remove `c_str` macro. While it's preferred to use C-string
   literals, there are two cases where `c_str` is helpful:
   - When working with macros, which already return a Rust string literal
     (e.g. `stringify!`).
   - When building macros, where we want to take a Rust string literal as an
     argument (for caller's convenience), but still use it as a C-string
     internally.
- Use Rust literals as arguments in macros (`new_mutex`, `new_condvar`,
   `new_mutex`). Use the `c_str` macro to convert these literals to C-string
   literals.
- Use `c_str` in kunit.rs for converting the output of `stringify!` to a
   `CStr`.
- Remove `DerefMut` implementation for `CString`.
v2 -> v3:
- Fix the commit message.
- Remove redundant braces in `use`, when only one item is imported.
v3 -> v4:
- Provide the `CStrExt` trait with `display()` method, which returns a
   `CStrDisplay` wrapper with `Display` implementation. This addresses
   the lack of `Display` implementation for `core::ffi::CStr`.
- Provide `from_bytes_with_nul_unchecked_mut()` method in `CStrExt`,
   which might be useful and is going to prevent manual, unsafe casts.
- Fix a typo (s/preffered/prefered/).
v4 -> v5:
- Keep the `test_cstr_display*` unit tests.

    

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Re: [PATCH RESEND v5] rust: str: Use `core::CStr`, remove the custom `CStr` implementation

Signed-off-by: Michal Rostecki vadorovsky@gmail.com