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Reduce MSRV to 1.61.0 #234

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Aug 8, 2023
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Reduce MSRV to 1.61.0 #234

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2 changes: 1 addition & 1 deletion Cargo.toml
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Expand Up @@ -16,7 +16,7 @@ authors = ["Joshua Liebow-Feeser <joshlf@google.com>"]
description = "Utilities for zero-copy parsing and serialization"
license = "BSD-2-Clause"
repository = "https://github.com/google/zerocopy"
rust-version = "1.65.0"
rust-version = "1.61.0"

exclude = [".*"]

Expand Down
92 changes: 41 additions & 51 deletions src/lib.rs
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Expand Up @@ -334,15 +334,23 @@ pub unsafe trait FromZeroes {
where
Self: Sized,
{
let size = mem::size_of::<Self>()
.checked_mul(len)
.expect("mem::size_of::<Self>() * len overflows `usize`");
let align = mem::align_of::<Self>();
// On stable Rust versions <= 1.64.0, `Layout::from_size_align` has a
// bug in which sufficiently-large allocations (those which, when
// rounded up to the alignment, overflow `isize`) are not rejected,
// which can cause undefined behavior. See #64 for details.
//
// TODO(#67): Once our MSRV is > 1.64.0, remove this assertion.
#[allow(clippy::as_conversions)]
let max_alloc = (isize::MAX as usize).saturating_sub(align);
assert!(size <= max_alloc);
// TODO(#2): Use `Layout::repeat` when `alloc_layout_extra` is
// stabilized.
let layout = Layout::from_size_align(
mem::size_of::<Self>()
.checked_mul(len)
.expect("mem::size_of::<Self>() * len overflows `usize`"),
mem::align_of::<Self>(),
)
.expect("total allocation size overflows `isize`");
let layout =
Layout::from_size_align(size, align).expect("total allocation size overflows `isize`");

// TODO(#61): Add a "SAFETY" comment and remove this `allow`.
#[allow(clippy::undocumented_unsafe_blocks)]
Expand Down Expand Up @@ -1265,12 +1273,16 @@ impl<T> Unalign<T> {
/// If `self` does not satisfy `mem::align_of::<T>()`, then
/// `self.deref_unchecked()` may cause undefined behavior.
pub const unsafe fn deref_unchecked(&self) -> &T {
// SAFETY: `self.get_ptr()` returns a raw pointer to a valid `T` at the
// same memory location as `self`. It has no alignment guarantee, but
// the caller has promised that `self` is properly aligned, so we know
// that the pointer itself is aligned, and thus that it is sound to
// create a reference to a `T` at this memory location.
unsafe { &*self.get_ptr() }
// SAFETY: `Unalign<T>` is `repr(transparent)`, so there is a valid `T`
// at the same memory location as `self`. It has no alignment guarantee,
// but the caller has promised that `self` is properly aligned, so we
// know that it is sound to create a reference to `T` at this memory
// location.
//
// We use `mem::transmute` instead of `&*self.get_ptr()` because
// dereferencing pointers is not stable in `const` on our current MSRV
// (1.56 as of this writing).
unsafe { mem::transmute(self) }
}

/// Returns a mutable reference to the wrapped `T` without checking
Expand Down Expand Up @@ -1518,6 +1530,10 @@ macro_rules! transmute {
// were to use `core::mem::transmute`, this macro would not work in
// `std` contexts in which `core` was not manually imported. This is
// not a problem for 2018 edition crates.
//
// Some older versions of Clippy have a bug in which they don't
// recognize the preceding safety comment.
#[allow(clippy::undocumented_unsafe_blocks)]
unsafe { $crate::__real_transmute(e) }
}
}}
Expand Down Expand Up @@ -2777,17 +2793,12 @@ mod alloc_support {

#[cfg(test)]
mod tests {
use core::convert::TryFrom as _;

use super::*;

#[test]
fn test_extend_vec_zeroed() {
// Test extending when there is an existing allocation.
let mut v: Vec<u64> = Vec::with_capacity(3);
v.push(100);
v.push(200);
v.push(300);
let mut v = vec![100u64, 200, 300];
extend_vec_zeroed(&mut v, 3);
assert_eq!(v.len(), 6);
assert_eq!(&*v, &[100, 200, 300, 0, 0, 0]);
Expand All @@ -2804,10 +2815,7 @@ mod alloc_support {
#[test]
fn test_extend_vec_zeroed_zst() {
// Test extending when there is an existing (fake) allocation.
let mut v: Vec<()> = Vec::with_capacity(3);
v.push(());
v.push(());
v.push(());
let mut v = vec![(), (), ()];
extend_vec_zeroed(&mut v, 3);
assert_eq!(v.len(), 6);
assert_eq!(&*v, &[(), (), (), (), (), ()]);
Expand All @@ -2830,30 +2838,21 @@ mod alloc_support {
drop(v);

// Insert at start.
let mut v: Vec<u64> = Vec::with_capacity(3);
v.push(100);
v.push(200);
v.push(300);
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 5);
assert_eq!(&*v, &[0, 0, 100, 200, 300]);
drop(v);

// Insert at middle.
let mut v: Vec<u64> = Vec::with_capacity(3);
v.push(100);
v.push(200);
v.push(300);
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 1, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[100, 0, 200, 300]);
drop(v);

// Insert at end.
let mut v: Vec<u64> = Vec::with_capacity(3);
v.push(100);
v.push(200);
v.push(300);
let mut v = vec![100u64, 200, 300];
insert_vec_zeroed(&mut v, 3, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[100, 200, 300, 0]);
Expand All @@ -2870,30 +2869,21 @@ mod alloc_support {
drop(v);

// Insert at start.
let mut v: Vec<()> = Vec::with_capacity(3);
v.push(());
v.push(());
v.push(());
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 0, 2);
assert_eq!(v.len(), 5);
assert_eq!(&*v, &[(), (), (), (), ()]);
drop(v);

// Insert at middle.
let mut v: Vec<()> = Vec::with_capacity(3);
v.push(());
v.push(());
v.push(());
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 1, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[(), (), (), ()]);
drop(v);

// Insert at end.
let mut v: Vec<()> = Vec::with_capacity(3);
v.push(());
v.push(());
v.push(());
let mut v = vec![(), (), ()];
insert_vec_zeroed(&mut v, 3, 1);
assert_eq!(v.len(), 4);
assert_eq!(&*v, &[(), (), (), ()]);
Expand Down Expand Up @@ -2962,7 +2952,7 @@ mod alloc_support {
}

#[test]
#[should_panic(expected = "total allocation size overflows `isize`: LayoutError")]
#[should_panic(expected = "assertion failed: size <= max_alloc")]
fn test_new_box_slice_zeroed_panics_isize_overflow() {
let max = usize::try_from(isize::MAX).unwrap();
let _ = u16::new_box_slice_zeroed((max / mem::size_of::<u16>()) + 1);
Expand Down Expand Up @@ -3753,7 +3743,7 @@ mod tests {
/// has had its bits flipped (by applying `^= 0xFF`).
///
/// `N` is the size of `t` in bytes.
fn test<const N: usize, T: FromBytes + AsBytes + Debug + Eq + ?Sized>(
fn test<T: FromBytes + AsBytes + Debug + Eq + ?Sized, const N: usize>(
t: &mut T,
bytes: &[u8],
post_mutation: &T,
Expand Down Expand Up @@ -3825,12 +3815,12 @@ mod tests {
};
let post_mutation_expected_a =
if cfg!(target_endian = "little") { 0x00_00_00_FE } else { 0xFF_00_00_01 };
test::<12, _>(
test::<_, 12>(
&mut Foo { a: 1, b: Wrapping(2), c: None },
expected_bytes.as_bytes(),
&Foo { a: post_mutation_expected_a, b: Wrapping(2), c: None },
);
test::<3, _>(
test::<_, 3>(
Unsized::from_mut_slice(&mut [1, 2, 3]),
&[1, 2, 3],
Unsized::from_mut_slice(&mut [0xFE, 2, 3]),
Expand Down
6 changes: 3 additions & 3 deletions tests/trybuild.rs
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Expand Up @@ -15,11 +15,11 @@
// - `tests/ui-msrv` - Contains symlinks to the `.rs` files in
// `tests/ui-nightly`, and contains `.err` and `.out` files for MSRV

#[rustversion::any(nightly)]
#[rustversion::nightly]
const SOURCE_FILES_GLOB: &str = "tests/ui-nightly/*.rs";
#[rustversion::all(stable, not(stable(1.65.0)))]
#[rustversion::stable(1.69.0)]
const SOURCE_FILES_GLOB: &str = "tests/ui-stable/*.rs";
#[rustversion::stable(1.65.0)]
#[rustversion::stable(1.61.0)]
const SOURCE_FILES_GLOB: &str = "tests/ui-msrv/*.rs";

#[test]
Expand Down
19 changes: 6 additions & 13 deletions tests/ui-msrv/transmute-illegal.stderr
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Expand Up @@ -2,20 +2,13 @@ error[E0277]: the trait bound `*const usize: AsBytes` is not satisfied
--> tests/ui-msrv/transmute-illegal.rs:10:30
|
10 | const POINTER_VALUE: usize = zerocopy::transmute!(&0usize as *const usize);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| |
| the trait `AsBytes` is not implemented for `*const usize`
| required by a bound introduced by this call
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `AsBytes` is not implemented for `*const usize`
|
= help: the following other types implement trait `AsBytes`:
f32
f64
i128
i16
i32
i64
i8
isize
= help: the following implementations were found:
<usize as AsBytes>
<f32 as AsBytes>
<f64 as AsBytes>
<i128 as AsBytes>
and $N others
note: required by a bound in `POINTER_VALUE::transmute`
--> tests/ui-msrv/transmute-illegal.rs:10:30
Expand Down
2 changes: 1 addition & 1 deletion zerocopy-derive/Cargo.toml
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Expand Up @@ -10,7 +10,7 @@ authors = ["Joshua Liebow-Feeser <joshlf@google.com>"]
description = "Custom derive for traits from the zerocopy crate"
license = "BSD-2-Clause"
repository = "https://github.com/google/zerocopy"
rust-version = "1.65.0"
rust-version = "1.61.0"

exclude = [".*"]

Expand Down
4 changes: 2 additions & 2 deletions zerocopy-derive/src/repr.rs
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Expand Up @@ -191,7 +191,7 @@ impl Repr {
let ident = path
.get_ident()
.ok_or_else(|| Error::new_spanned(meta, "unrecognized representation hint"))?;
match format!("{ident}").as_str() {
match format!("{}", ident).as_str() {
"u8" => return Ok(Repr::U8),
"u16" => return Ok(Repr::U16),
"u32" => return Ok(Repr::U32),
Expand Down Expand Up @@ -221,7 +221,7 @@ impl Repr {
impl Display for Repr {
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), fmt::Error> {
if let Repr::Align(n) = self {
return write!(f, "repr(align({n}))");
return write!(f, "repr(align({}))", n);
}
write!(
f,
Expand Down
6 changes: 3 additions & 3 deletions zerocopy-derive/tests/trybuild.rs
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Expand Up @@ -15,11 +15,11 @@
// - `tests/ui-msrv` - Contains symlinks to the `.rs` files in
// `tests/ui-nightly`, and contains `.err` and `.out` files for MSRV

#[rustversion::any(nightly)]
#[rustversion::nightly]
const SOURCE_FILES_GLOB: &str = "tests/ui-nightly/*.rs";
#[rustversion::all(stable, not(stable(1.65.0)))]
#[rustversion::stable(1.69.0)]
const SOURCE_FILES_GLOB: &str = "tests/ui-stable/*.rs";
#[rustversion::stable(1.65.0)]
#[rustversion::stable(1.61.0)]
const SOURCE_FILES_GLOB: &str = "tests/ui-msrv/*.rs";

#[test]
Expand Down