[`new_without_default`]: Now emits on const fns #10903

Centri3 · 2023-06-07T02:35:31Z

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

rustbot · 2023-06-07T02:35:36Z

r? @llogiq

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

bors · 2023-08-18T16:12:55Z

☔ The latest upstream changes (presumably #11280) made this pull request unmergeable. Please resolve the merge conflicts.

llogiq · 2023-08-19T11:57:57Z

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.

llogiq · 2023-10-17T05:12:56Z

Ping?

Centri3 · 2023-10-18T04:23:47Z

Sorry, will rebase and add that note later today

llogiq · 2023-10-21T06:13:09Z

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

llogiq · 2023-10-21T12:46:22Z

I'll just

@rustbot author

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

robertbastian · 2024-01-04T12:05:38Z

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.

llogiq · 2024-01-04T13:50:39Z

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

Centri3 · 2024-02-16T07:24:27Z

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

Centri3 · 2024-02-16T07:45:34Z

Nevermind. got it to work

@bors r=llogiq

bors · 2024-02-16T07:45:36Z

📌 Commit f0adfe7 has been approved by llogiq

It is now in the queue for this repository.

bors · 2024-02-16T07:47:39Z

⌛ Testing commit f0adfe7 with merge 9064cc8...

[`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

bors · 2024-02-16T07:52:29Z

💔 Test failed - checks-action_test

Centri3 · 2024-02-16T07:54:00Z

MacOS again, @bors retry

bors · 2024-02-16T07:55:07Z

⌛ Testing commit f0adfe7 with merge 61daf67...

bors · 2024-02-16T08:02:54Z

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 61daf67 to master...

bors · 2024-02-16T08:02:54Z

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 61daf67 to master...

bors · 2024-02-16T08:03:52Z

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

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 <[email protected]>

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_*` `cfg`s 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). Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1770-2024-03-21 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [3] Link: Rust-for-Linux#2 [4] Link: rust-lang/rust#120062 [5] Link: rust-lang/rust#120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: rust-lang/rust#117772 [8] Link: rust-lang/rust-clippy#10903 [9] Link: rust-lang/rust#119365 [10] Link: rust-lang/rust#119364 [11] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [12] Link: rust-lang/rust#120932 [13] Link: rust-lang/rust#120969 [14] Link: rust-lang/rust#121202 [15] Link: rust-lang/rust#121237 [16] Signed-off-by: Miguel Ojeda <[email protected]>

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 <[email protected]>

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. 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_*` `cfg`s 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 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]. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [3] Link: Rust-for-Linux#2 [4] Link: rust-lang/rust#120062 [5] Link: rust-lang/rust#120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: rust-lang/rust#117772 [8] Link: rust-lang/rust-clippy#10903 [9] Link: rust-lang/rust#119365 [10] Link: rust-lang/rust#119364 [11] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [12] Link: rust-lang/rust#120932 [13] Link: rust-lang/rust#120969 [14] Link: rust-lang/rust#121202 [15] Link: rust-lang/rust#121237 [16] Signed-off-by: Miguel Ojeda <[email protected]>

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. 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_*` `cfg`s 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 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` 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]. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [3] Link: Rust-for-Linux#2 [4] Link: rust-lang/rust#120062 [5] Link: rust-lang/rust#120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: rust-lang/rust#117772 [8] Link: rust-lang/rust-clippy#10903 [9] Link: rust-lang/rust#119365 [10] Link: rust-lang/rust#119364 [11] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [12] Link: rust-lang/rust#120932 [13] Link: rust-lang/rust#120969 [14] Link: rust-lang/rust#121202 [15] Link: rust-lang/rust#121237 [16] Signed-off-by: Miguel Ojeda <[email protected]>

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 <[email protected]> Reviewed-by: Alice Ryhl <[email protected]> Reviewed-by: Boqun Feng <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Miguel Ojeda <[email protected]>

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. 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_*` `cfg`s 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 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` 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 `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]. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [3] Link: Rust-for-Linux#2 [4] Link: rust-lang/rust#120062 [5] Link: rust-lang/rust#120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: rust-lang/rust#117772 [8] Link: rust-lang/rust-clippy#10903 [9] Link: rust-lang/rust#119365 [10] Link: rust-lang/rust#119364 [11] Link: https://lore.kernel.org/rust-for-linux/[email protected]/ [12] Link: rust-lang/rust#119618 [13] Link: rust-lang/rust#120932 [14] Link: https://github.com/rust-lang/rust/pull/120932/files#diff-e6fc1622c46054cd46b1d225c5386c5554564b3b0fa8a03c2dc2d8627a1079d9 [15] Link: rust-lang/rust#120969 [16] Link: Rust-for-Linux#354 [17] Link: rust-lang/rust#121202 [18] Link: rust-lang/rust#121237 [19] Reviewed-by: Alice Ryhl <[email protected]> Link: https://lore.kernel.org/r/[email protected] [ Added a few more details and links I mentioned in the list. - Miguel ] Signed-off-by: Miguel Ojeda <[email protected]>

rustbot assigned llogiq Jun 7, 2023

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Centri3 closed this Feb 16, 2024

Centri3 force-pushed the new_without_default branch from 2891dab to 237fbdd Compare February 16, 2024 07:22

lint new_without_default on const fns too

f0adfe7

Centri3 reopened this Feb 16, 2024

bors merged commit 61daf67 into rust-lang:master Feb 16, 2024
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[`new_without_default`]: Now emits on const fns #10903

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[new_without_default]: Now emits on const fns #10903

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[`new_without_default`]: Now emits on const fns #10903

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