Hi all I have debug --enable-rust in tor-0.3.2.9 on x86-android target, with compare with arm-android target, find more details about this issue. debug output on x86-android in ffi.rs: Feb 05 02:01:00.161 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning RustString self 0xbf8ec7f8 RUST: rust_welcome_string Tor is running with Rust integration. Please report any bugs you encouter. 0xbf8ec7f8 C: &rust_str = 0xbf8ec870, rust_str = 0xa889a880 //printf(" C: &rust_str = %p, rust_str = %p\n", &rust_str, rust_str); Segmentation fault // when I try to print str:RustString address in rust_str_get, as following pub unsafe extern "C" fn rust_str_get(str: RustString) -> *const c_char { println!(" RUST: rust_str_get &str = {:p} ", &str); debug output on arm-android in ffi.rs: Feb 05 10:12:01.092 [notice] Tor can't help you if you use it wrong! Learn how to be safe at https://www.torproject.org/download/download#warning RustString self 0xbe810814 RUST: rust_welcome_string Tor is running with Rust integration. Please report any bugs you encouter. 0xbe810814 C: &rust_str = 0xbe810890, rust_str = 0xb66eb000 RUST: rust_str_get &str = 0xbe810810 //println!(" RUST: rust_str_get &str = {:p} ", &str); //? I don't known why the address is different with the address return in rust_welcome_string // but two address is very close // in C code, the address of rust_str is also very close to the address in RUST, it make sense. RustString self 0xbe810810 RUST: rust_str_get str = Tor is running with Rust integration. Please report any bugs you encouter. Feb 05 10:12:01.093 [notice] Tor is running with Rust integration. Please report any bugs you encouter. Compare the two debug output, rust_str return from rust_welcome_string is correct on two target. but in rust_str_get, rust_str passed from C code is invalid on x86-android target. the RUST code runing very well on x86-android target, only have issue work with C code -- Thanks PGP Fingerprint: F7BA D6CE 6592 77C7 0D2E 3BD5 5479 A15E B305 B8FE