rust-lang/rust

impl<'a> Encode<VipsJpegImage<'a>> for VipsJpegImage<'a> {
    fn encode(&self, quality: u8) -> Result<VipsJpegImage<'a>, Box<Error>> {
        println!("before unsafe encode");
        let mut buf: *mut c_void = null_mut();
        let mut result_size: usize = 0;
        let img = unsafe {
            println!("before jpegsave_buffer");
            vips::vips_jpegsave_buffer(
                self.img,
                &mut buf,
                &mut result_size,
                "Q\0".as_ptr(),
                quality as i32,
                NULL_LIST,
            );
            println!("after jpegsave_buffer");
            println!(">>>>> {:#?}", result_size);
            println!(">>>>> {:#?}", CStr::from_ptr(buf as *const c_char));
            vips::vips_image_new_from_buffer(buf as *const c_void, result_size, NULL_LIST)
        };
        println!("after unsafe encode");
        result(img)
    }
}

Hi, I'm facing a segfault issue with libvips bindings. Regardless of the specific use case, I wonder if someone could point out possible issues in the code. most likely it should be something related to the mutable buf used to write the jpeg output in. If I do run the code multiple times, sometimes a jpeg actually get correctly written there, but quite often it just segfaults. So I guess there may be some source of randomness on where the memory address ends up. I saw this pattern around to pass a void pointer to C functions, but I'm not sure if it is the proper way.