On Monday, July 15th, 2024 at 17:46, Michal Rostecki vadorovsky@gmail.com wrote:
On 14.07.24 19:01, Björn Roy Baron wrote:
On Sunday, July 14th, 2024 at 18:02, Michal Rostecki vadorovsky@gmail.com wrote:
`CStr` became a part of `core` library in Rust 1.75, therefore there is no need to keep the custom implementation.
`core::CStr` behaves generally the same as the removed implementation, with the following differences:
- It does not implement `Display` (but implements `Debug`).
- It does not provide `from_bytes_with_nul_unchecked_mut` method.
- It was used only in `DerefMut` implementation for `CString`. This change replaces it with a manual cast to `&mut CStr`.
- Otherwise, having such a method is not really desirable. `CStr` is a reference type or `str` are usually not supposed to be modified.
- It has `as_ptr()` method instead of `as_char_ptr()`, which also returns `*const c_char`.
Rust also introduces C literals (`c""`), so the `c_str` macro is removed here as well.
Signed-off-by: Michal Rostecki vadorovsky@gmail.com
rust/kernel/error.rs | 7 +- rust/kernel/init.rs | 8 +- rust/kernel/kunit.rs | 16 +- rust/kernel/net/phy.rs | 2 +- rust/kernel/prelude.rs | 4 +- rust/kernel/str.rs | 490 +----------------------------------- rust/kernel/sync.rs | 13 +- rust/kernel/sync/condvar.rs | 5 +- rust/kernel/sync/lock.rs | 6 +- rust/kernel/workqueue.rs | 10 +- scripts/rustdoc_test_gen.rs | 4 +- 11 files changed, 57 insertions(+), 508 deletions(-)
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diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs index 68605b633e73..af0017e56c0e 100644 --- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -46,7 +46,7 @@ //! } //! //! let foo = pin_init!(Foo { -//! a <- new_mutex!(42, "Foo::a"), +//! a <- new_mutex!(42, c"Foo::a"),
That we need a CStr here seems a bit of an internal implementation detail. Maybe keep accepting a regular string literal and converting it to a CStr internally? If others think what you have here is fine, I don't it mind all that much though.
The names passed to `new_mutex`, `new_condvar`, `new_spinlock` etc. are immediately passed in the FFI calls (`__mutex_init`, `__init_waitqueue_head`, `__spin_lock_init`) [0][1][2]. In fact, I don't see any internal usage, where using Rust &str would be beneficial. Am I missing something?
Converting a &str to &CStr inside `Mutex::new` or `CondVar::new` would require allocating a new buffer, larger by 1, to include the nul byte. Doing that for every new mutex or condvar seems a bit wasteful to me.
The names passed to `new_mutex!` and such are literals known at compile time. This means we can keep adding the nul terminator at compile time without allocating any extra buffer. Basically just adapting the current implementation of `optional_name!` to produce an `core::ffi::&CStr` rather than a `kernel::str::CStr` from a regular string literal is enough to avoid having to explicitly use C string literals in those macro invocations. This way users don't need to know that internally an `&CStr` is used.
[0] https://github.com/Rust-for-Linux/linux/blob/b1263411112305acf2af72872859146... [1] https://github.com/Rust-for-Linux/linux/blob/b1263411112305acf2af72872859146... [2] https://github.com/Rust-for-Linux/linux/blob/b1263411112305acf2af72872859146...
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