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Improve cast_ptr_alignment lint

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* print alignment in bytes in the lint message
* ignore ZST left-hand types
This commit is contained in:
Florian Gilcher 2019-07-06 11:40:14 +02:00
parent 8744e8ed26
commit aa72cac87a
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GPG key ID: E7B51D33F8EBF61B
3 changed files with 16 additions and 6 deletions
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16
clippy_lints/src/types.rs
View file

@ -1210,17 +1210,25 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Casts {
if_chain! {
if let ty::RawPtr(from_ptr_ty) = &cast_from.sty;
if let ty::RawPtr(to_ptr_ty) = &cast_to.sty;
if let Some(from_align) = cx.layout_of(from_ptr_ty.ty).ok().map(|a| a.align.abi);
if let Some(to_align) = cx.layout_of(to_ptr_ty.ty).ok().map(|a| a.align.abi);
if from_align < to_align;
if let Ok(from_layout) = cx.layout_of(from_ptr_ty.ty);
if let Ok(to_layout) = cx.layout_of(to_ptr_ty.ty);
if from_layout.align.abi < to_layout.align.abi;
// with c_void, we inherently need to trust the user
if !is_c_void(cx, from_ptr_ty.ty);
// when casting from a ZST, we don't know enough to properly lint
if !from_layout.is_zst();
then {
span_lint(
cx,
CAST_PTR_ALIGNMENT,
expr.span,
&format!("casting from `{}` to a more-strictly-aligned pointer (`{}`)", cast_from, cast_to)
&format!(
"casting from `{}` to a more-strictly-aligned pointer (`{}`) ({} < {} bytes)",
cast_from,
cast_to,
from_layout.align.abi.bytes(),
to_layout.align.abi.bytes(),
),
);
}
}

2
tests/ui/cast_alignment.rs
View file

@ -22,4 +22,6 @@ fn main() {
// For c_void, we should trust the user. See #2677
(&1u32 as *const u32 as *const std::os::raw::c_void) as *const u32;
(&1u32 as *const u32 as *const libc::c_void) as *const u32;
// For ZST, we should trust the user. See #4256
(&1u32 as *const u32 as *const ()) as *const u32;
}

4
tests/ui/cast_alignment.stderr
View file

@ -1,4 +1,4 @@
error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`)
error: casting from `*const u8` to a more-strictly-aligned pointer (`*const u16`) (1 < 2 bytes)
--> $DIR/cast_alignment.rs:12:5
|
LL | (&1u8 as *const u8) as *const u16;
@ -6,7 +6,7 @@ LL | (&1u8 as *const u8) as *const u16;
|
= note: `-D clippy::cast-ptr-alignment` implied by `-D warnings`
error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`)
error: casting from `*mut u8` to a more-strictly-aligned pointer (`*mut u16`) (1 < 2 bytes)
--> $DIR/cast_alignment.rs:13:5
|
LL | (&mut 1u8 as *mut u8) as *mut u16;