Whether the default handling is reset if the SIGILL signal is received by a handler specified to the signal function (§4.7.1.1)
SIGILL is not generated under DOS. It is included for ANSI compatibility. DOS does not provide a way for an application to regain control when an illegal instruction occurs. However, a user can issue a signal function and later trigger that signal via an explicit call to the raise function. As with all signals under DOS, the signal handler is set to the default action (SIG_DFL) before the user's signal handler gets control.