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Reject invalid #[repr(packed)] attributes
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They will be rejected by rustc but, we should not rely on the behavior
of rustc that rejects them.
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@taiki-e
taiki-e committed Apr 13, 2021
1 parent 8b411b3 commit 8dd9b64
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Showing 5 changed files with 89 additions and 86 deletions.
45 changes: 33 additions & 12 deletions pin-project-internal/src/pin_project/derive.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ use quote::{format_ident, quote, quote_spanned, ToTokens};
use syn::{
parse_quote, token, visit_mut::VisitMut, Attribute, Data, DataEnum, DeriveInput, Error, Field,
Fields, FieldsNamed, FieldsUnnamed, Generics, Ident, Index, Lifetime, LifetimeDef, Meta,
MetaList, NestedMeta, Result, Token, Type, Variant, Visibility, WhereClause,
MetaList, MetaNameValue, NestedMeta, Result, Token, Type, Variant, Visibility, WhereClause,
};

use super::{
Expand Down Expand Up @@ -326,7 +326,7 @@ fn parse_struct<'a>(
generate: &mut GenerateTokens,
) -> Result<()> {
// Do this first for a better error message.
let packed_check = ensure_not_packed(&cx.orig, fields)?;
let packed_check = ensure_not_packed(&cx.orig, Some(fields))?;

validate_struct(cx.orig.ident, fields)?;

Expand Down Expand Up @@ -414,8 +414,12 @@ fn parse_enum<'a>(
));
}

// We don't need to check for `#[repr(packed)]`,
// since it does not apply to enums.
// #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
// However, we should not rely on the behavior of rustc that rejects this.
// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
//
// Do this first for a better error message.
ensure_not_packed(&cx.orig, None)?;

validate_enum(*brace_token, variants)?;

Expand Down Expand Up @@ -996,28 +1000,45 @@ fn make_proj_impl(
/// * Checks the attributes of structs to ensure there is no `[repr(packed)]`.
/// * Generates a function that borrows fields without an unsafe block and
/// forbidding `unaligned_references` lint.
fn ensure_not_packed(orig: &OriginalType<'_>, fields: &Fields) -> Result<TokenStream> {
fn ensure_not_packed(orig: &OriginalType<'_>, fields: Option<&Fields>) -> Result<TokenStream> {
for meta in orig.attrs.iter().filter_map(|attr| attr.parse_meta().ok()) {
if let Meta::List(list) = meta {
if list.path.is_ident("repr") {
for repr in list.nested.iter() {
match repr {
NestedMeta::Meta(Meta::Path(path))
| NestedMeta::Meta(Meta::List(MetaList { path, .. }))
if path.is_ident("packed") =>
{
return Err(error!(
repr,
"#[pin_project] attribute may not be used on #[repr(packed)] types"
));
| NestedMeta::Meta(Meta::NameValue(MetaNameValue { path, .. })) => {
if path.is_ident("packed") {
let msg = if fields.is_none() {
// #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
// However, we should not rely on the behavior of rustc that rejects this.
// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
"#[repr(packed)] attribute should be applied to a struct or union"
} else if let NestedMeta::Meta(Meta::NameValue(..)) = repr {
// #[repr(packed = "")] is not valid format of #[repr(packed)] and will be
// rejected by rustc.
// However, we should not rely on the behavior of rustc that rejects this.
// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
"#[repr(packed)] attribute should not be name-value pair"
} else {
"#[pin_project] attribute may not be used on #[repr(packed)] types"
};
return Err(error!(repr, msg));
}
}
_ => {}
NestedMeta::Lit(..) => {}
}
}
}
}
}

let fields = match fields {
Some(fields) => fields,
None => return Ok(TokenStream::new()),
};

// Workaround for https://github.com/taiki-e/pin-project/issues/32
// Through the tricky use of proc macros, it's possible to bypass
// the above check for the `repr` attribute.
Expand Down
4 changes: 4 additions & 0 deletions tests/ui/pin_project/packed-enum.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,9 @@
use pin_project::pin_project;

// #[repr(packed)] cannot be apply on enums and will be rejected by rustc.
// However, we should not rely on the behavior of rustc that rejects this.
// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001

#[repr(packed)] //~ ERROR E0517
enum E1 {
V(()),
Expand Down
50 changes: 31 additions & 19 deletions tests/ui/pin_project/packed-enum.stderr
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Original file line number Diff line number Diff line change
@@ -1,30 +1,42 @@
error: #[repr(packed)] attribute should be applied to a struct or union
--> $DIR/packed-enum.rs:13:8
|
13 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^

error: #[repr(packed)] attribute should be applied to a struct or union
--> $DIR/packed-enum.rs:18:8
|
18 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^

error[E0517]: attribute should be applied to a struct or union
--> $DIR/packed-enum.rs:3:8
|
3 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^
4 | / enum E1 {
5 | | V(()),
6 | | }
| |_- not a struct or union
--> $DIR/packed-enum.rs:7:8
|
7 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^
8 | / enum E1 {
9 | | V(()),
10 | | }
| |_- not a struct or union

error[E0517]: attribute should be applied to a struct or union
--> $DIR/packed-enum.rs:9:8
--> $DIR/packed-enum.rs:13:8
|
9 | #[repr(packed)] //~ ERROR E0517
13 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^
10 | / enum E2 {
11 | | V(()),
12 | | }
14 | / enum E2 {
15 | | V(()),
16 | | }
| |_- not a struct or union

error[E0517]: attribute should be applied to a struct or union
--> $DIR/packed-enum.rs:14:8
--> $DIR/packed-enum.rs:18:8
|
14 | #[repr(packed)] //~ ERROR E0517
18 | #[repr(packed)] //~ ERROR E0517
| ^^^^^^
15 | #[pin_project]
16 | / enum E3 {
17 | | V(()),
18 | | }
19 | #[pin_project]
20 | / enum E3 {
21 | | V(()),
22 | | }
| |_- not a struct or union
19 changes: 13 additions & 6 deletions tests/ui/pin_project/packed-name-value.rs
View file
Original file line number Diff line number Diff line change
@@ -1,17 +1,24 @@
use pin_project::pin_project;

#[repr(packed = "")] //~ ERROR E0552
struct S1 {
f: (),
}
// #[repr(packed = "")] is not valid format of #[repr(packed)] and will be
// rejected by rustc.
// However, we should not rely on the behavior of rustc that rejects this.
// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001

// https://github.com/taiki-e/pin-project/pull/324#discussion_r612388001
// https://github.com/rust-lang/rust/issues/83921
// #[repr(packed = "")] //~ ERROR E0552
// struct S1 {
// f: (),
// }

#[pin_project]
#[repr(packed = "")] //~ ERROR E0552
#[repr(packed = "")] //~ ERROR attribute should not be name-value pair
struct S2 {
f: (),
}

#[repr(packed = "")] //~ ERROR E0552
#[repr(packed = "")] //~ ERROR attribute should not be name-value pair
#[pin_project]
struct S3 {
f: (),
Expand Down
57 changes: 8 additions & 49 deletions tests/ui/pin_project/packed-name-value.stderr
View file
Original file line number Diff line number Diff line change
@@ -1,52 +1,11 @@
error: internal compiler error: unrecognized representation hint
--> $DIR/packed-name-value.rs:3:8
|
3 | #[repr(packed = "")] //~ ERROR E0552
| ^^^^^^^^^^^
|
= note: delayed at compiler/rustc_attr/src/builtin.rs:940:32

error: internal compiler error: unrecognized representation hint
--> $DIR/packed-name-value.rs:9:8
|
9 | #[repr(packed = "")] //~ ERROR E0552
| ^^^^^^^^^^^
|
= note: delayed at compiler/rustc_attr/src/builtin.rs:940:32

error: internal compiler error: unrecognized representation hint
--> $DIR/packed-name-value.rs:14:8
error: #[repr(packed)] attribute should not be name-value pair
--> $DIR/packed-name-value.rs:16:8
|
14 | #[repr(packed = "")] //~ ERROR E0552
16 | #[repr(packed = "")] //~ ERROR attribute should not be name-value pair
| ^^^^^^^^^^^
|
= note: delayed at compiler/rustc_attr/src/builtin.rs:940:32

thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', compiler/rustc_errors/src/lib.rs:1018:13
stack backtrace:
0: _rust_begin_unwind
1: std::panicking::begin_panic_fmt
2: rustc_errors::HandlerInner::flush_delayed
3: <rustc_errors::HandlerInner as core::ops::drop::Drop>::drop
4: core::ptr::drop_in_place<rustc_session::parse::ParseSess>
5: <alloc::rc::Rc<T> as core::ops::drop::Drop>::drop
6: core::ptr::drop_in_place<rustc_interface::interface::Compiler>
7: rustc_span::with_source_map
8: rustc_interface::interface::create_compiler_and_run
9: scoped_tls::ScopedKey<T>::set
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.53.0-nightly (d0695c908 2021-04-12) running on x86_64-apple-darwin

note: compiler flags: -C embed-bitcode=no -C split-debuginfo=unpacked -C debuginfo=2 --crate-type bin

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
error: #[repr(packed)] attribute should not be name-value pair
--> $DIR/packed-name-value.rs:21:8
|
21 | #[repr(packed = "")] //~ ERROR attribute should not be name-value pair
| ^^^^^^^^^^^

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