Wrong alignment of struct #1034
Comments
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Reduced by Reduced by |
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For alignment problem: this little program outputs Generated bindings looks like: #![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
#[repr(C)]
#[derive(Debug, Default, Copy)]
pub struct S2 {
pub _bitfield_1: u16,
pub __bindgen_align: [u8; 0usize],
}
#[test]
fn bindgen_test_layout_S2() {
assert_eq!(
::std::mem::size_of::<S2>(),
2usize,
concat!("Size of: ", stringify!(S2))
);
assert_eq!(
::std::mem::align_of::<S2>(),
1usize,
concat!("Alignment of ", stringify!(S2))
);
}
impl Clone for S2 {
fn clone(&self) -> Self {
*self
}
}
impl S2 {
#[inline]
pub fn new_bitfield_1() -> u16 {
0
}
}And this is how it looks in IR |
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Interesting -- it looks like the layout libclang gives us says |
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I compiled with
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Oops, my comment #1034 (comment) contains copy-pasta issue. It tells that it outputs Sorry about that! Fixed version: #include <stdio.h>
struct S2 {
unsigned : 11;
};
int main() {
printf("sizeof(S2)=%lu,alignof(S2)=%lu\n", sizeof(S2), alignof(S2));
}returns This makes things a little clearer. |
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Is it possible to solve now? If I understand correctly to make this struct #[repr(C)]
#[derive(Debug, Default, Copy)]
pub struct S2 {
pub _bitfield_1: u16,
pub __bindgen_align: [u8; 0usize],
}to have alignment of 1 we should have |
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Depends on #849 and rust-lang/rust#33626 |
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It seems that It appears that we actually need to use |
Use `repr(packed)` If struct requires explicit alignment of 1. Fixes #1034
Input C/C++ Header
Generated by C-Smith:
Bindgen Invocation
Actual Results
Expected Results
No layout test failures.
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