linux-kernel - [PATCH v8 26/29] rust: str: test: replace `alloc::format`

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Message-ID: <20241001150008.183102-27-dakr@kernel.org>
Date: Tue,  1 Oct 2024 17:00:01 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: ojeda@...nel.org,
	alex.gaynor@...il.com,
	wedsonaf@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me,
	a.hindborg@...sung.com,
	aliceryhl@...gle.com,
	akpm@...ux-foundation.org
Cc: daniel.almeida@...labora.com,
	faith.ekstrand@...labora.com,
	boris.brezillon@...labora.com,
	lina@...hilina.net,
	mcanal@...lia.com,
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	jhubbard@...dia.com,
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	linux-kernel@...r.kernel.org,
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	Danilo Krummrich <dakr@...nel.org>
Subject: [PATCH v8 26/29] rust: str: test: replace `alloc::format`

The current implementation of tests in str.rs use `format!` to format
strings for comparison, which, internally, creates a new `String`.

In order to prepare for getting rid of Rust's alloc crate, we have to
cut this dependency. Instead, implement `format!` for `CString`.

Note that for userspace tests, `Kmalloc`, which is backing `CString`'s
memory, is just a type alias to `Cmalloc`.

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
Reviewed-by: Gary Guo <gary@...yguo.net>
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/str.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 209ad1bb1a49..726329530338 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -523,7 +523,28 @@ macro_rules! c_str {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use alloc::format;
+
+    struct String(CString);
+
+    impl String {
+        fn from_fmt(args: fmt::Arguments<'_>) -> Self {
+            String(CString::try_from_fmt(args).unwrap())
+        }
+    }
+
+    impl Deref for String {
+        type Target = str;
+
+        fn deref(&self) -> &str {
+            self.0.to_str().unwrap()
+        }
+    }
+
+    macro_rules! format {
+        ($($f:tt)*) => ({
+            &*String::from_fmt(kernel::fmt!($($f)*))
+        })
+    }
 
     const ALL_ASCII_CHARS: &'static str =
         "\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\
-- 
2.46.1