some panic safety issues that cause double free in unwind branch

[cchanging]

Hi there, we detected a few potential panic safety issues in this library.
double free will appear mainly caused by panic happened between Box::from_raw and std::mem::forget.
example as follows:

rose-tools/rose-lib-ffi/src/zms.rs

Lines 18 to 28 in 11fc557

	pub unsafe extern "C" fn mesh_read(mesh: *mut Mesh, path: *const libc::c_char) -> bool {
	let mut zms = Box::from_raw(mesh);
	let path_str = CStr::from_ptr(path).to_str().unwrap_or_default();
	let p = PathBuf::from(path_str);
	let res = zms.read_from_path(&p).is_ok();
	std::mem::forget(zms);
	res
	}

When panic occurs in let res = zms.read_from_path(&p).is_ok(); or the other codes between Box::from_raw and std::mem::forget , the zms will be dropped in unwinding and make the mesh an empty pointer, which will cause double-free bug in the upper function.
You can use mem:ManuallyDrop::new(Box::from_raw(mesh)) instead to avoid this problem.
This type of bug is difficult to detect with test cases, but it does pose a security risk.