On 8/15/24 9:30 AM, Alice Ryhl wrote:
On Thu, Aug 15, 2024 at 12:46 AM Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
On Wed, Aug 14, 2024 at 10:42:28AM +0200, Alice Ryhl wrote:
+#[macro_export]
+macro_rules! kvec {
+ () => (
+ {
+ $crate::alloc::KVec::new()
+ }
+ );
+ ($elem:expr; $n:expr) => (
+ {
+ $crate::alloc::KVec::from_elem($elem, $n, GFP_KERNEL)
+ }
+ );
+ ($($x:expr),+ $(,)?) => (
+ {
+ match $crate::alloc::KBox::new([$($x),+], GFP_KERNEL) {
+ Ok(b) => Ok($crate::alloc::KBox::into_vec(b)),
+ Err(e) => Err(e),
Hmm. This currently generates code that:
1. Creates the array.
2. Allocates the memory.
3. Moves the array into the box.
Whereas the stdlib macro swaps step 1 and 2.
Isn't stdlib [1] doing the same thing I do?
[1] https://doc.rust-lang.org/1.80.1/src/alloc/macros.rs.html#49
Stdlib is using something called #[rustc_box] which has the effect I described.
You can do the same by utilizing new_uninit. A sketch:
match KBox::<[_; _]>::new_uninit(GFP_KERNEL) {
How do we get the size here? `#![feature(generic_arg_infer)]` seems to be
unstable.
It probably works if you don't specify the type at all:
`KBox::new_uninit`. But you should double check.
That works, thanks.
Ok(b) => Ok(KVec::from(KBox::write(b, [$($x),+]))),
Err(e) => Err(e),
}
