The siginterrupt() function changes the restart behaviour when a system call is interrupted by the signal sig. If the flag argument is false (0), then system calls will be restarted if interrupted by the specified signal sig. This is the default behaviour in Linux. However, when a new signal handler is specified with the signal(2) function, the system call is interrupted by default.
If the flags argument is true (1) and no data has been transferred, then a system call interrupted by the signal sig will return -1 and the global variable errno will be set to EINTR.