rust: zerocopy: update to v0.8.52

Update our vendored copy of `zerocopy` (and `zerocopy-derive`) to v0.8.52.

Most SPDX identifiers have been added upstream at our request [1]
(without parentheses -- supporting them is an issue on the kernel side,
but it does already reduce our differences). The CSS one for `rustdoc`
was added too [2], but will be picked up in a later version.

For `zerocopy`, enable `--cfg no_fp_fmt_parse`, which was added at our
request to avoid our local workaround [3]. This means one less difference,
thus indicate so in our `README.md`.

For `zerocopy-derive`, enable `--cfg zerocopy_unstable_linux`. This
allows us to use `#[derive(zerocopy_derive::most_traits)]`, a new feature
upstream added for us [4]. We noticed a minor doc render bug [5], which
will be fixed for a future version too.

The following script may be used to check for the remaining differences:

    for path in $(cd rust/zerocopy-derive/ && find . -type f ! -name README.md); do
        curl --silent --show-error --location \
            https://github.com/google/zerocopy/raw/v0.8.52/zerocopy/zerocopy-derive/src/$path |
            git diff --no-index - rust/zerocopy-derive/$path &&
            echo $path: OK
    done

    for path in $(cd rust/zerocopy/ && find . -type f ! -name README.md); do
        curl --silent --show-error --location \
            https://github.com/google/zerocopy/raw/v0.8.52/zerocopy/$path |
            git diff --no-index - rust/zerocopy/$path &&
            echo $path: OK
    done

Cc: Joshua Liebow-Feeser <joshlf@google.com>
Cc: Jack Wrenn <jswrenn@google.com>
Link: https://github.com/google/zerocopy/issues/3428 [1]
Link: https://github.com/google/zerocopy/issues/3457 [2]
Link: https://github.com/google/zerocopy/issues/3426 [3]
Link: https://github.com/google/zerocopy/pull/3416 [4]
Link: https://github.com/google/zerocopy/issues/3466 [5]
Acked-by: Nicolas Schier <n.schier@fritz.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260625231919.692444-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

10 files changed, 88 insertions, 33 deletions

diff --git a/rust/zerocopy-derive/README.md b/rust/zerocopy-derive/README.md
index 110f4a401778..2a3dcf1212af 100644
--- a/rust/zerocopy-derive/README.md
+++ b/rust/zerocopy-derive/README.md
@@ -1,14 +1,14 @@
 # `zerocopy-derive`
 
-These source files come from the Rust `zerocopy-derive` crate, version v0.8.50
-(released 2026-05-31), hosted in the <https://github.com/google/zerocopy>
+These source files come from the Rust `zerocopy-derive` crate, version v0.8.52
+(released 2026-06-09), hosted in the <https://github.com/google/zerocopy>
 repository, licensed under "BSD-2-Clause OR Apache-2.0 OR MIT" and only
-modified to add the SPDX license identifiers and to remove the generation of
+modified to tweak the SPDX license identifiers and to remove the generation of
 non-ASCII identifiers.
 
 For copyright details, please see:
 
-    https://github.com/google/zerocopy/blob/v0.8.50/README.md?plain=1
-    https://github.com/google/zerocopy/blob/v0.8.50/LICENSE-BSD
-    https://github.com/google/zerocopy/blob/v0.8.50/LICENSE-APACHE
-    https://github.com/google/zerocopy/blob/v0.8.50/LICENSE-MIT
+    https://github.com/google/zerocopy/blob/v0.8.52/README.md?plain=1
+    https://github.com/google/zerocopy/blob/v0.8.52/LICENSE-BSD
+    https://github.com/google/zerocopy/blob/v0.8.52/LICENSE-APACHE
+    https://github.com/google/zerocopy/blob/v0.8.52/LICENSE-MIT
diff --git a/rust/zerocopy-derive/derive/from_bytes.rs b/rust/zerocopy-derive/derive/from_bytes.rs
index d693a63b7645..66d820f6ad4c 100644
--- a/rust/zerocopy-derive/derive/from_bytes.rs
+++ b/rust/zerocopy-derive/derive/from_bytes.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 use proc_macro2::{Span, TokenStream};
 use syn::{
     parse_quote, Data, DataEnum, DataStruct, DataUnion, Error, Expr, ExprLit, ExprUnary, Lit, UnOp,
diff --git a/rust/zerocopy-derive/derive/into_bytes.rs b/rust/zerocopy-derive/derive/into_bytes.rs
index ad52a6b45d28..0103a78d087f 100644
--- a/rust/zerocopy-derive/derive/into_bytes.rs
+++ b/rust/zerocopy-derive/derive/into_bytes.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 use proc_macro2::{Span, TokenStream};
 use quote::quote;
 use syn::{Data, DataEnum, DataStruct, DataUnion, Error, Type};
diff --git a/rust/zerocopy-derive/derive/known_layout.rs b/rust/zerocopy-derive/derive/known_layout.rs
index fddffd167c82..d0c4cecfff15 100644
--- a/rust/zerocopy-derive/derive/known_layout.rs
+++ b/rust/zerocopy-derive/derive/known_layout.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{parse_quote, Data, Error, Type};
@@ -87,7 +87,6 @@ fn derive_known_layout_for_repr_c_struct<'a>(
     };
 
     let inner_extras = {
-        let leading_fields_tys = leading_fields_tys.clone();
         let methods = make_methods(*trailing_field_ty);
         let (_, ty_generics, _) = ctx.ast.generics.split_for_impl();
 
diff --git a/rust/zerocopy-derive/derive/mod.rs b/rust/zerocopy-derive/derive/mod.rs
index 665ba7da55a8..b3839fcf73c9 100644
--- a/rust/zerocopy-derive/derive/mod.rs
+++ b/rust/zerocopy-derive/derive/mod.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 pub mod from_bytes;
 pub mod into_bytes;
 pub mod known_layout;
@@ -15,8 +15,8 @@ use crate::{
     util::{Ctx, DataExt, FieldBounds, ImplBlockBuilder, Trait},
 };
 
-pub(crate) fn derive_immutable(ctx: &Ctx, _top_level: Trait) -> TokenStream {
-    match &ctx.ast.data {
+pub(crate) fn derive_immutable(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    Ok(match &ctx.ast.data {
         Data::Struct(strct) => {
             ImplBlockBuilder::new(ctx, strct, Trait::Immutable, FieldBounds::ALL_SELF).build()
         }
@@ -26,7 +26,7 @@ pub(crate) fn derive_immutable(ctx: &Ctx, _top_level: Trait) -> TokenStream {
         Data::Union(unn) => {
             ImplBlockBuilder::new(ctx, unn, Trait::Immutable, FieldBounds::ALL_SELF).build()
         }
-    }
+    })
 }
 
 pub(crate) fn derive_hash(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
@@ -97,16 +97,20 @@ pub(crate) fn derive_split_at(ctx: &Ctx, _top_level: Trait) -> Result<TokenStrea
     match &ctx.ast.data {
         Data::Struct(_) => {}
         Data::Enum(_) | Data::Union(_) => {
-            return Err(Error::new(Span::call_site(), "can only be applied to structs"));
+            return ctx
+                .error_or_skip(Error::new(Span::call_site(), "can only be applied to structs"));
         }
     };
 
     if repr.get_packed().is_some() {
-        return Err(Error::new(Span::call_site(), "must not have #[repr(packed)] attribute"));
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must not have #[repr(packed)] attribute",
+        ));
     }
 
     if !(repr.is_c() || repr.is_transparent()) {
-        return Err(Error::new(
+        return ctx.error_or_skip(Error::new(
             Span::call_site(),
             "must have #[repr(C)] or #[repr(transparent)] in order to guarantee this type's layout is splitable",
         ));
@@ -116,7 +120,7 @@ pub(crate) fn derive_split_at(ctx: &Ctx, _top_level: Trait) -> Result<TokenStrea
     let trailing_field = if let Some(((_, _, trailing_field), _)) = fields.split_last() {
         trailing_field
     } else {
-        return Err(Error::new(Span::call_site(), "must at least one field"));
+        return ctx.error_or_skip(Error::new(Span::call_site(), "must at least one field"));
     };
 
     let zerocopy_crate = &ctx.zerocopy_crate;
diff --git a/rust/zerocopy-derive/derive/try_from_bytes.rs b/rust/zerocopy-derive/derive/try_from_bytes.rs
index a3e4a75631a5..44f083328786 100644
--- a/rust/zerocopy-derive/derive/try_from_bytes.rs
+++ b/rust/zerocopy-derive/derive/try_from_bytes.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{
@@ -531,8 +531,8 @@ fn derive_has_field_struct_union(ctx: &Ctx, data: &dyn DataExt) -> TokenStream {
                 data,
                 Trait::ProjectField {
                     variant_id: variant_id.clone(),
-                    field: field.clone(),
-                    field_id: field_id.clone(),
+                    field,
+                    field_id,
                     invariants: parse_quote!((Aliasing, Alignment, #zerocopy_crate::invariant::Initialized)),
                 },
                 FieldBounds::None,
diff --git a/rust/zerocopy-derive/derive/unaligned.rs b/rust/zerocopy-derive/derive/unaligned.rs
index d6dea0a11f1e..7c97d62e2dcb 100644
--- a/rust/zerocopy-derive/derive/unaligned.rs
+++ b/rust/zerocopy-derive/derive/unaligned.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 use proc_macro2::{Span, TokenStream};
 use syn::{Data, DataEnum, DataStruct, DataUnion, Error};
 
diff --git a/rust/zerocopy-derive/lib.rs b/rust/zerocopy-derive/lib.rs
index c517ea7db1eb..88599e750894 100644
--- a/rust/zerocopy-derive/lib.rs
+++ b/rust/zerocopy-derive/lib.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 // Copyright 2019 The Fuchsia Authors
 //
 // Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
@@ -129,6 +129,40 @@ derive!(ByteHash => derive_hash => crate::derive::derive_hash);
 derive!(ByteEq => derive_eq => crate::derive::derive_eq);
 derive!(SplitAt => derive_split_at => crate::derive::derive_split_at);
 
+#[cfg_attr(zerocopy_unstable_linux, doc(hidden))]
+#[proc_macro_derive(most_traits, attributes(zerocopy))]
+pub fn most_traits(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let ast = syn::parse_macro_input!(ts as DeriveInput);
+    let ctx = match Ctx::try_from_derive_input(ast) {
+        Ok(ctx) => ctx,
+        Err(e) => return e.into_compile_error().into(),
+    }
+    .skip_on_error();
+
+    // top-level traits for which to attempt a derive
+    let derives: [(fn(&Ctx, Trait) -> _, _); 6] = [
+        (crate::derive::known_layout::derive, Trait::KnownLayout),
+        (crate::derive::derive_immutable, Trait::Immutable),
+        (crate::derive::from_bytes::derive_from_bytes, Trait::FromBytes),
+        (crate::derive::into_bytes::derive_into_bytes, Trait::IntoBytes),
+        (crate::derive::derive_split_at, Trait::SplitAt),
+        (crate::derive::unaligned::derive_unaligned, Trait::Unaligned),
+    ];
+
+    let mut tokens = proc_macro2::TokenStream::new();
+    for (derive, t) in derives {
+        tokens.extend(derive(&ctx, t))
+    }
+
+    // We wrap in `const_block` as a backstop in case any derive fails
+    // to wrap its output in `const_block` (and thus fails to annotate)
+    // with the full set of `#[allow(...)]` attributes).
+    let ts = const_block([Some(tokens)]);
+    #[cfg(test)]
+    crate::util::testutil::check_hygiene(ts.clone());
+    ts.into()
+}
+
 /// Deprecated: prefer [`FromZeros`] instead.
 #[deprecated(since = "0.8.0", note = "`FromZeroes` was renamed to `FromZeros`")]
 #[doc(hidden)]
diff --git a/rust/zerocopy-derive/repr.rs b/rust/zerocopy-derive/repr.rs
index 74fd376d9fda..1525e94302d1 100644
--- a/rust/zerocopy-derive/repr.rs
+++ b/rust/zerocopy-derive/repr.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 // Copyright 2019 The Fuchsia Authors
 //
 // Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
diff --git a/rust/zerocopy-derive/util.rs b/rust/zerocopy-derive/util.rs
index 5ba5228e2a44..5c5e9d3bdcb8 100644
--- a/rust/zerocopy-derive/util.rs
+++ b/rust/zerocopy-derive/util.rs
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
-
+//
 // Copyright 2019 The Fuchsia Authors
 //
 // Licensed under a BSD-style license <LICENSE-BSD>, Apache License, Version 2.0
@@ -98,6 +98,11 @@ impl Ctx {
         }
     }
 
+    pub(crate) fn skip_on_error(mut self) -> Self {
+        self.skip_on_error = true;
+        self
+    }
+
     pub(crate) fn core_path(&self) -> TokenStream {
         let zerocopy_crate = &self.zerocopy_crate;
         quote!(#zerocopy_crate::util::macro_util::core_reexport)
@@ -106,20 +111,21 @@ impl Ctx {
     pub(crate) fn cfg_compile_error(&self) -> TokenStream {
         // By checking both during the compilation of the proc macro *and* in
         // the generated code, we ensure that `--cfg
-        // zerocopy_unstable_derive_on_error` need only be passed *either* when
+        // zerocopy_unstable_linux` need only be passed *either* when
         // compiling this crate *or* when compiling the user's crate. The former
         // is preferable, but in some situations (such as when cross-compiling
         // using `cargo build --target`), it doesn't get propagated to this
         // crate's build by default.
-        if cfg!(zerocopy_unstable_derive_on_error) {
+        if cfg!(zerocopy_unstable_linux) {
             quote!()
         } else if let Some(span) = self.on_error_span {
             let core = self.core_path();
-            let error_message = "`on_error` is experimental; pass '--cfg zerocopy_unstable_derive_on_error' to enable";
+            let error_message =
+                "`on_error` is experimental; pass '--cfg zerocopy_unstable_linux' to enable";
             quote::quote_spanned! {span=>
                 #[allow(unused_attributes, unexpected_cfgs)]
                 const _: () = {
-                    #[cfg(not(zerocopy_unstable_derive_on_error))]
+                    #[cfg(not(zerocopy_unstable_linux))]
                     #core::compile_error!(#error_message);
                 };
             }
@@ -612,6 +618,20 @@ impl<'a> ImplBlockBuilder<'a> {
             }
         };
 
+        let zerocopy_bounds =
+            field_type_bounds
+                .into_iter()
+                .chain(padding_check_bound)
+                .chain(self_bounds)
+                .map(|bound| {
+                    if self.ctx.skip_on_error {
+                        parse_quote!(for<'zc> #bound)
+                    } else {
+                        bound.clone()
+                    }
+                })
+                .collect::<Vec<_>>();
+
         let bounds = self
             .ctx
             .ast
@@ -621,9 +641,7 @@ impl<'a> ImplBlockBuilder<'a> {
             .map(|where_clause| where_clause.predicates.iter())
             .into_iter()
             .flatten()
-            .chain(field_type_bounds.iter())
-            .chain(padding_check_bound.iter())
-            .chain(self_bounds.iter());
+            .chain(zerocopy_bounds.iter());
 
         // The parameters with trait bounds, but without type defaults.
         let mut params: Vec<_> = self