internal error: sizeof(string_view) != 32

Input C/C++ Header

#pragma once

#include <string>

void f(std::string_view);

Bindgen Invocation

$ bindgen test.h -- -x c++ -std=c++17

Actual Results

#[repr(C)]
#[derive(Debug, Copy, Clone)]
pub struct std_basic_string_view<_CharT> {
    pub _M_len: std_size_t,
    pub _M_str: *const _CharT,
    pub _phantom_0: ::std::marker::PhantomData<::std::cell::UnsafeCell<_CharT>>,
}
...
#[test]
fn __bindgen_test_layout_std_basic_string_open0_char_std_char_traits_open1_char_close1_std_allocator_open1_char_close1_close0_instantiation(
) {
    assert_eq!(
        ::std::mem::size_of::<std_basic_string<::std::os::raw::c_char>>(),
        32usize,
        concat!(
            "Size of template specialization: ",
            stringify!(std_basic_string<::std::os::raw::c_char>)
        )
    );
    assert_eq!(
        ::std::mem::align_of::<std_basic_string<::std::os::raw::c_char>>(),
        8usize,
        concat!(
            "Alignment of template specialization: ",
            stringify!(std_basic_string<::std::os::raw::c_char>)
        )
    );
}

Expected Results

As you can see "unit" tests expect that size of struct with c_char will be 32,
this tests failed on Linux/amd64, because of size of equals 16.

Reproduce the issue with test.h and the shown bindgen command using C++17. Inspect the generated std_basic_string_view layout and its emitted size and alignment test; done means this input no longer produces an incorrect failing layout assertion on Linux/amd64.