Function secp256k1::ffi::secp256k1_ecdsa_sign

pub unsafe fn secp256k1_ecdsa_sign(
    cx: *const Context,
    sig: *mut Signature,
    msg32: *const c_uchar,
    sk: *const c_uchar,
    _noncefn: NonceFn,
    _noncedata: *const c_void
) -> c_int

Sets sig to msg32||sk