Function secp256k1_sys::secp256k1_schnorrsig_verify

pub unsafe extern "C" fn secp256k1_schnorrsig_verify(
    cx: *const Context,
    sig64: *const c_uchar,
    msg32: *const c_uchar,
    msglen: size_t,
    pubkey: *const XOnlyPublicKey
) -> c_int

Available on non-secp256k1_fuzz only.