int lk;],
[syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],[],
[AC_MSG_ERROR([SYS_gettid and SYS_futex required for --enable-linux-futex])])
int lk;],
[syscall (SYS_gettid); syscall (SYS_futex, &lk, 0, 0, 0);])],[],
[AC_MSG_ERROR([SYS_gettid and SYS_futex required for --enable-linux-futex])])