Wrong layout for union with bitfields

[pepyakin]

See original issue #1034

Input C/C++ Header

Generated by C-Smith and reduced by creduce:

union U4 {
  unsigned : 1
};

Bindgen Invocation

$ bindgen input.h --with-derive-partialeq --with-derive-eq

Actual Results

running 1 test
test bindgen_test_layout_U4 ... FAILED

failures:

---- bindgen_test_layout_U4 stdout ----
	thread 'bindgen_test_layout_U4' panicked at 'assertion failed: `(left == right)`
  left: `2`,
 right: `1`: Size of: U4', /var/folders/cd/c9707gm91qj22fkb99clygfm0000gn/T/bindings.rs.XXXXXX.E24MhMan:58:4

failures:
    bindgen_test_layout_U4

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

Expected Results

No layout test failures.

[pepyakin]

Seems like we have a different problem in the size case.

Let's consider this header:

union U4 {
  unsigned : 1
};

in generated bindings assert test is failing

assert_eq!(
    ::std::mem::size_of::<U4>(),
    1usize,
    concat!("Size of: ", stringify!(U4))
);

and it makes sense if we look at U4 definition:

#[repr(C)]
#[derive(Copy)]
pub struct U4 {
    pub _bitfield_1: u8,
    pub bindgen_union_field: u8,
}

there are 2 disjoint fields, and this is clearly wrong.

I suppose in this case we shouldn't generate _bitfield_1 but should refer bindgen_union_field in bitfield's accessors.

[emilio]

This is a dupe of #744, I believe.

[pepyakin]

Agree, closing.