[`new_without_default`]: Now emits on const fns by Centri3 · Pull Request #10903 · rust-lang/rust-clippy (original) (raw)

While Default::default is not const, it can still call const new; there's no reason this shouldn't be linted as well.

fixes #10877

changelog: [new_without_default]: Now emits on const fns

r? @llogiq

(rustbot has picked a reviewer for you, use r? to override)

I'd like to see a diagnostic note about the const situation, like: "While default() is not const, its implementation still can call const code", just to preempt questions.

Sorry, will rebase and add that note later today

No rush, I just want to spare you yet another rebase.

I'll just

@rustbot author

for now so it's not sitting idly in my queue.

rustbot added S-waiting-on-author

Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status)

and removed S-waiting-on-review

Status: Awaiting review from the assignee but also interested parties

labels

Oct 21, 2023

I'd like to see a diagnostic note about the const situation, like: "While default() is not const, its implementation still can call const code", just to preempt questions.

Is this really necessary? The ability to call const methods is pretty basic knowledge.

Ok, I won't further delay this PR, any additional notes and diagnostics can be a followup. r=me when rebased.

Ok, nice, no idea what went wrong while rebasing...
I can't reopen so I'll create a new PR. Damn

Nevermind. got it to work

@bors r=llogiq

📌 Commit f0adfe7 has been approved by llogiq

It is now in the queue for this repository.

bors added a commit that referenced this pull request

Feb 16, 2024

[new_without_default]: Now emits on const fns

While Default::default is not const, it can still call const new; there's no reason this shouldn't be linted as well.

fixes #10877

changelog: [new_without_default]: Now emits on const fns

1 similar comment

👀 Test was successful, but fast-forwarding failed: 422 Changes must be made through a pull request.

ojeda added a commit to ojeda/linux that referenced this pull request

Apr 1, 2024

In Rust 1.78.0, Clippy suggests to implement Default even when new() is const, since Default::default() may call const functions even if it is not const itself [1]:

error: you should consider adding a `Default` implementation for `LockClassKey`
  --> rust/kernel/sync.rs:31:5
   |
31 | /     pub const fn new() -> Self {
32 | |         Self(Opaque::uninit())
33 | |     }
   | |_____^

Thus implement it.

Link: rust-lang/rust-clippy#10903 [1] Signed-off-by: Miguel Ojeda ojeda@kernel.org

ojeda added a commit to ojeda/linux that referenced this pull request

Apr 1, 2024

This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

Unstable features

There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the kernel crate is still new_uninit.

However, since we are finally dropping our alloc fork [3], all the unstable features used by alloc (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintanance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions.

It also means that, ignoring non-language/library features, we are currently left with just the few language features needed to implement the kernel Arc, the new_uninit library feature, the compiler_builtins marker and the few no_* cfgs we pass when compiling core/alloc.

Please see [4] for details.

Required changes

LLVM's data layout

Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus update the data layout in our custom target specification for x86 so that the compiler does not complain about the mismatch:

error: data-layout for target `target-5559158138856098584`,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
differs from LLVM target's `x86_64-linux-gnu` default layout,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specification files. Meanwhile, if we want to support other LLVM versions used in rustc (e.g. for LTO), we will need to add some extra logic (e.g. conditional on LLVM's version, or extracting the data layout from an existing built-in target specification).

`unused_imports`

Rust's unused_imports lint covers both unused and redudant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus the previous commit cleaned them up.

Clippy's `new_without_default`

Clippy now suggests to implement Default even when new() is const, since Default::default() may call const functions even if it is not const itself [9]. Thus the previous commit added the implementation.

Other changes in Rust

Rust 1.78.0 introduces feature(asm_goto) [10] [11]. This feature was discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics, including a test case for the Linux kernel's VTABLE use case [13].

Rust 1.78.0 with debug assertions enabled (i.e. -Cdebug-assertions=y, kernel's CONFIG_RUST_DEBUG_ASSERTIONS=y) will now always check all unsafe preconditions, without a way to opt-out for particular cases [14].

Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new --check-cfg feature [15] [16].

`alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update alloc anymore, since we are dropping our alloc fork [3].

As a bonus, even if that series is not applied, the new compiler release happens to build cleanly the existing alloc too (i.e. the previous version's).

ojeda added a commit to ojeda/linux that referenced this pull request

Apr 1, 2024

In the upcoming Rust 1.78.0, Clippy suggests to implement Default even when new() is const, since Default::default() may call const functions even if it is not const itself [1]:

error: you should consider adding a `Default` implementation for `LockClassKey`
  --> rust/kernel/sync.rs:31:5
   |
31 | /     pub const fn new() -> Self {
32 | |         Self(Opaque::uninit())
33 | |     }
   | |_____^

Thus implement it.

Link: rust-lang/rust-clippy#10903 [1] Signed-off-by: Miguel Ojeda ojeda@kernel.org

ojeda added a commit to ojeda/linux that referenced this pull request

Apr 1, 2024

This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

Unstable features

There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the kernel crate is still new_uninit.

However, since we are finally dropping our alloc fork [3], all the unstable features used by alloc (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintenance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions.

Please see [4] for details.

Required changes

LLVM's data layout

error: data-layout for target `target-5559158138856098584`,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
differs from LLVM target's `x86_64-linux-gnu` default layout,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

`unused_imports`

Rust's unused_imports lint covers both unused and redundant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus one of the previous patches cleaned them up.

Clippy's `new_without_default`

Clippy now suggests to implement Default even when new() is const, since Default::default() may call const functions even if it is not const itself [9]. Thus one of the previous patches implemented it.

Other changes in Rust

Rust 1.78.0 introduced feature(asm_goto) [10] [11]. This feature was discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics, including a test case for the Linux kernel's VTABLE use case [13].

Rust 1.78.0 with debug assertions enabled (i.e. -Cdebug-assertions=y, kernel's CONFIG_RUST_DEBUG_ASSERTIONS=y) now always checks all unsafe preconditions, without a way to opt-out for particular cases [14].

Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new --check-cfg feature [15] [16].

`alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update alloc anymore, since we are dropping our alloc fork [3].

ojeda added a commit to ojeda/linux that referenced this pull request

Apr 1, 2024

This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

Unstable features

There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the kernel crate is still new_uninit.

However, since we are finally dropping our alloc fork [3], all the unstable features used by alloc (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintenance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions.

Please see [4] for details.

Required changes

LLVM's data layout

error: data-layout for target `target-5559158138856098584`,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
differs from LLVM target's `x86_64-linux-gnu` default layout,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specifications. Meanwhile, if we want to support other LLVM versions used in rustc (e.g. for LTO), we will need to add some extra logic (e.g. conditional on LLVM's version, or extracting the data layout from an existing built-in target specification).

`unused_imports`

Rust's unused_imports lint covers both unused and redundant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus one of the previous patches cleaned them up.

Clippy's `new_without_default`

Other changes in Rust

Rust 1.78.0 introduced feature(asm_goto) [10] [11]. This feature was discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics, including a test case for the Linux kernel's VTABLE use case [13].

Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new --check-cfg feature [15] [16].

`alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update alloc anymore, since we are dropping our alloc fork [3].

ojeda added a commit to ojeda/linux that referenced this pull request

May 5, 2024

In the upcoming Rust 1.78.0, Clippy suggests to implement Default even when new() is const, since Default::default() may call const functions even if it is not const itself [1]:

error: you should consider adding a `Default` implementation for `LockClassKey`
  --> rust/kernel/sync.rs:31:5
   |
31 | /     pub const fn new() -> Self {
32 | |         Self(Opaque::uninit())
33 | |     }
   | |_____^

Thus implement it.

Link: rust-lang/rust-clippy#10903 [1] Reviewed-by: Benno Lossin benno.lossin@proton.me Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Boqun Feng boqun.feng@gmail.com Link: https://lore.kernel.org/r/20240401212303.537355-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda ojeda@kernel.org

ojeda added a commit to ojeda/linux that referenced this pull request

May 5, 2024

This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

It is much smaller than previous upgrades, since the alloc fork was dropped in commit 9d0441b ("rust: alloc: remove our fork of the alloc crate") [3].

Unstable features

There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the kernel crate is still new_uninit.

However, since we finally dropped our alloc fork [3], all the unstable features used by alloc (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintenance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions.

Please see [4] for details.

Required changes

LLVM's data layout

error: data-layout for target `target-5559158138856098584`,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
differs from LLVM target's `x86_64-linux-gnu` default layout,
`e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

`unused_imports`

Rust's unused_imports lint covers both unused and redundant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus one of the previous patches cleaned them up.

Clippy's `new_without_default`

Other changes in Rust

Rust 1.78.0 introduced feature(asm_goto) [10] [11]. This feature was discussed in the past [12].

Rust 1.78.0 introduced feature(const_refs_to_static) [13] to allow referencing statics in constants and extended feature(const_mut_refs) to allow raw mutable pointers in constants. Together, this should cover the kernel's VTABLE use case. In fact, the implementation [14] in upstream Rust added a test case for it [15].

Rust 1.78.0 with debug assertions enabled (i.e. -Cdebug-assertions=y, kernel's CONFIG_RUST_DEBUG_ASSERTIONS=y) now always checks all unsafe preconditions, though without a way to opt-out for particular cases [16]. It would be ideal to have a way to selectively disable certain checks per-call site for this one (i.e. not just per check but for particular instances of a check), even if the vast majority of the checks remain in place [17].

Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new --check-cfg feature [18] [19].

`alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update alloc anymore, since we dropped our alloc fork [3].

[new_without_default]: Now emits on const fns by Centri3 · Pull Request #10903 · rust-lang/rust-clippy (original) (raw)

Unstable features

Required changes

LLVM's data layout

unused_imports

Clippy's new_without_default

Other changes in Rust

alloc upgrade and reviewing

Unstable features

Required changes

LLVM's data layout

unused_imports

Clippy's new_without_default

Other changes in Rust

alloc upgrade and reviewing

Unstable features

Required changes

LLVM's data layout

unused_imports

Clippy's new_without_default

Other changes in Rust

alloc upgrade and reviewing

Unstable features

Required changes

LLVM's data layout

unused_imports

Clippy's new_without_default

Other changes in Rust

alloc upgrade and reviewing

[`new_without_default`]: Now emits on const fns by Centri3 · Pull Request #10903 · rust-lang/rust-clippy (original) (raw)

`unused_imports`

Clippy's `new_without_default`

`alloc` upgrade and reviewing

`unused_imports`

Clippy's `new_without_default`

`alloc` upgrade and reviewing

`unused_imports`

Clippy's `new_without_default`

`alloc` upgrade and reviewing

`unused_imports`

Clippy's `new_without_default`

`alloc` upgrade and reviewing