SIGSEGV when passing *const c_char to bindgen function

[JustSoup321]

So I am wrapping bindgen generated unsafe wrappers for a C library (in this case EFL) with safe Rust. Currently, I am stuck facing a SIGSEGV (Address boundary error) when attempting to pass *const c_char from the libc crate. Currently, my code looks like this:

pub fn win_util_standard_add(name: &str, title: &str) -> *mut Evas_Object {
    let cname = std::ffi::CString::new(name).expect("CString::new() failed");
    let cname_ptr: *const c_char = cname.as_ptr();
    let ctitle = std::ffi::CString::new(title).expect("CString::new() failed");
    let ctitle_ptr: *const c_char = ctitle.as_ptr();

    unsafe { efl_sys::elm_win_util_standard_add(cname_ptr, ctitle_ptr) }
}

efl_sys::elm_win_util_standard_add() takes two *const c_chars. What am I doing wrong?

I am very new to working with unsafe Rust and ffi in general, so please excuse my confusion.

Obligatory Repository

[jumpnbrownweasel]

One possibility is that the owned variables (cname and ctitle) are being dropped on the Rust side, meaning their memory is freed, while the pointers (cname_ptr and ctitle_ptr) are still being used on the C side. You could try leaking them to see if that fixes it, as a test.

[JustSoup321]

Thank you for the response. I edited the code to add:

std::mem::forget(cname);
std::mem::forget(ctitle);

before returning the result of the unsafe block, but that still results in the same error.

Edit:

I tried leaking different parts of my program to see if the error was actually in something else. It turns out that the issue was in:

pub fn init() {
    let args = std::env::args()
        .map(|arg| CString::new(arg).unwrap())
        .collect::<Vec<CString>>();
    let c_args = args
        .iter()
        .map(|arg| arg.as_ptr())
        .collect::<Vec<*const c_char>>();

    unsafe { efl_sys::elm_init(c_args.len() as c_int, c_args.as_ptr() as *mut *mut c_char) };
}

where the function was dropping the args and c_args while the C function still had the pointers to them.

[jumpnbrownweasel]

Great, glad you found it.