[libvirt] [PATCH Rust 3/4] fix pointer type of macro used to convert rs string to c string

In this commit we also add todo and warning to avoid using them + remove them in future. Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui(a)canonical.com&gt; --- src/lib.rs | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/src/lib.rs b/src/lib.rs index 77bf4a9..64d49cd 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -99,12 +99,31 @@ macro_rules! c_chars_to_string { } +// Those two macros are not completely safe and we should probably +// stop using them to avoid possibility of pointers dangling. The +// memory may be freed too early. +// +// To avoid that, the right pattern would be: +// +// let cstring = CString::new(rs_string).unwrap(); +// unsafe { +// some_c_function(cstring.as_ptr() as *const libc::c_char); +// } +// +// So we ensure the pointer passed to 'some_c_function()' will live +// until 'cstring' exists. +// +// TODO(sahid): fix code + remove macros. + macro_rules! string_to_c_chars { - ($x:expr) => (::std::ffi::CString::new($x).unwrap().as_ptr()) + ($x:expr) => ( + ::std::ffi::CString::new($x).unwrap().as_ptr() as *const libc::c_char) } macro_rules! string_to_mut_c_chars { - ($x:expr) => (::std::ffi::CString::new($x).unwrap().into_raw()) + ($x:expr) => ( + // Usage of this should ensure deallocation. + ::std::ffi::CString::new($x).unwrap().into_raw() as *mut libc::c_char) } macro_rules! impl_from { -- 2.17.1