Unaligned Pointer Read

[petesmc]

This test using a i8 results in an unaligned pointer read...

rust-fitsio/fitsio/src/headers.rs

Line 246 in 1972db6

hdu.write_key(&mut f, "ONE", 1i8).unwrap();

... due to

&value as *const $t as *mut c_void, 

... in the below.

rust-fitsio/fitsio/src/headers.rs

Lines 102 to 125 in 1972db6

	impl WritesKey for $t {
	fn write_key(f: &mut FitsFile, name: &str, value: Self) -> Result<()> {
	let c_name = ffi::CString::new(name)?;
	let mut status = 0;
	let datatype = u8::from($datatype);
	unsafe {
	fits_write_key(
	f.fptr.as_mut() as *mut _,
	datatype as _,
	c_name.as_ptr(),
	&value as *const $t as *mut c_void,
	ptr::null_mut(),
	&mut status,
	);
	}
	check_status(status)
	}
	}
	};
	}
	writes_key_impl_int!(i8, DataType::TSHORT);

Which calls ffpkyj in the cfitsio library like so:

ffpkyj(fptr, keyname, (LONGLONG) *(short *) value, comm, status); // <--- pointer to i8 gets converted into pointer to short.

I believe to fix this, you need to convert i8 -> i16 given you are using TSHORT, OR map i8 to TBYTE instead.

[simonrw]

Hi, thanks for reporting this issue, and I'm glad you're using the project! You are absolutely right, the types do not match up for u8.

Do you have a minimal example which I can use to reproduce this issue, and make sure it doesn't happen again?

[petesmc]

Sorry nothing I can share at the moment. I detected it because I'm rewriting part of cfitsio in rust which in debug mode checks for misaligned pointer reads.

[simonrw]

Ok thanks. I've merged in a fix and am ok to not include a test for now. Can you use the latest main commit and test for me please?

[simonrw]

@petesmc have you had a chance to test my fix?

[petesmc]

Looks good for bytes, but think you need to update the u16/i16 as well to TUSHORT/TSHORT

[simonrw]

@petesmc done, can you check again?