incorrect results for structs with tail packing on x86-64 Linux

[froydnj]

Input C/C++ Header

template<typename T>
class LinkedListElement
{
public:
  LinkedListElement();
  ~LinkedListElement();

private:
  LinkedListElement* next;
  LinkedListElement* prev;
  const bool isSentinel;
};

class SchedulerGroup : public LinkedListElement<SchedulerGroup>
{
public:
  SchedulerGroup();
  ~SchedulerGroup();

private:
  bool isRunning;
  unsigned long eventCount;
  void* targets[8];
  void* threads[8];

public:
  virtual void DoThings();
  virtual void DoOtherThings();
};

Bindgen Invocation

$ bindgen --no-derive-debug --no-derive-copy --generate types --rustfmt-bindings tail-packing.cpp

Actual Results

ERROR:bindgen::codegen::struct_layout: Calculated wrong layout for SchedulerGroup, too more 8 bytes
/* automatically generated by rust-bindgen */

#[repr(C)]
pub struct LinkedListElement {
    pub next: *mut LinkedListElement,
    pub prev: *mut LinkedListElement,
    pub isSentinel: bool,
}
#[repr(C)]
pub struct SchedulerGroup__bindgen_vtable(::std::os::raw::c_void);
#[repr(C)]
pub struct SchedulerGroup {
    pub vtable_: *const SchedulerGroup__bindgen_vtable,
    pub _base: LinkedListElement,
    pub isRunning: bool,
    pub eventCount: ::std::os::raw::c_ulong,
    pub targets: [*mut ::std::os::raw::c_void; 8usize],
    pub threads: [*mut ::std::os::raw::c_void; 8usize],
}
#[test]
fn bindgen_test_layout_SchedulerGroup() {
    assert_eq!(
        ::std::mem::size_of::<SchedulerGroup>(),
        168usize,
        concat!("Size of: ", stringify!(SchedulerGroup))
    );
    assert_eq!(
        ::std::mem::align_of::<SchedulerGroup>(),
        8usize,
        concat!("Alignment of ", stringify!(SchedulerGroup))
    );
    assert_eq!(
        unsafe { &(*(0 as *const SchedulerGroup)).isRunning as *const _ as usize },
        25usize,
        concat!(
            "Alignment of field: ",
            stringify!(SchedulerGroup),
            "::",
            stringify!(isRunning)
        )
    );
    assert_eq!(
        unsafe { &(*(0 as *const SchedulerGroup)).eventCount as *const _ as usize },
        32usize,
        concat!(
            "Alignment of field: ",
            stringify!(SchedulerGroup),
            "::",
            stringify!(eventCount)
        )
    );
    assert_eq!(
        unsafe { &(*(0 as *const SchedulerGroup)).targets as *const _ as usize },
        40usize,
        concat!(
            "Alignment of field: ",
            stringify!(SchedulerGroup),
            "::",
            stringify!(targets)
        )
    );
    assert_eq!(
        unsafe { &(*(0 as *const SchedulerGroup)).threads as *const _ as usize },
        104usize,
        concat!(
            "Alignment of field: ",
            stringify!(SchedulerGroup),
            "::",
            stringify!(threads)
        )
    );
}
#[test]fn __bindgen_test_layout_LinkedListElement_open0_SchedulerGroup_close0_instantiation ( ){
    assert_eq!(
        ::std::mem::size_of::<LinkedListElement>(),
        24usize,
        concat!(
            "Size of template specialization: ",
            stringify!(LinkedListElement)
        )
    );
    assert_eq!(
        ::std::mem::align_of::<LinkedListElement>(),
        8usize,
        concat!(
            "Alignment of template specialization: ",
            stringify!(LinkedListElement)
        )
    );
}

Expected Results

There should not be an error about the incorrect layout of SchedulerGroup; bindgen has failed to take into account that isRunning will be packed into the unused space of LinkedListElement. The generated test for the layout of SchedulerGroup will also fail as a result of this.

[emilio]

I believe the packing issue is #404.

[emilio]

Which is #380 itself.

[froydnj]

Yeah, this is the same sort of issue as #380; not really obvious from #380's title, though. :)