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sigvector(2) sigvector(2)

(TO BE OBSOLETED)

NAME

sigvector - software signal facilities

SYNOPSIS

#include <signal.h>

int sigvector(

int sig,

const struct sigvec *vec,

struct sigvec *ovec

);

DESCRIPTION

The system deﬁnes a set of signals that can be delivered to a process. The set of signals is deﬁned in sig-

nal(5), along with the meaning and side effects of each signal. This manual entry, along with those for sig-

block(2), sigsetmask(2), sigpause(3C), and sigspace(2), deﬁnes an alternate mechanism for handling these

signals that ensures the delivery of signals and the integrity of signal handling procedures. The facilities

described here should not be used in the same program as signal(2).

With the sigvector() interface, signal delivery resembles the occurrence of a hardware interrupt: the

signal is blocked from further occurrence, the current process context is saved, and a new one is built. A

process can specify a handler function to be invoked when a signal is delivered, or specify that a signal

should be blocked or ignored. A process can also specify that a default action should be taken by the system

when a signal occurs. It is possible to ensure a minimum amount of stack space for processing signals

using sigspace() (see sigspace(2)).

All signals have the same priority. Signal routines execute with the signal that causes their invocation to

be blocked, although other signals can yet occur. A global signal mask deﬁnes the set of signals currently

blocked from delivery to a process. The signal mask for a process is initializedfrom that of its parent (nor-

mally 0). It can be changed with a sigblock(), sigsetmask() ,orsigpause() call, or when a sig-

nal is delivered to the process.

A signal mask is represented as a

long, with one bit representing each signal being blocked. The follow-

ing macro deﬁned in <signal.h> is used to convert a signal number to its corresponding bit in the mask:

#define sigmask(signo) (1L << (signo-1))

When a signal condition arises for a process, the signal is added to a set of signals pending for the process.

If the signal is not currently blocked by the process, it is delivered to the process. When a signal is

delivered, the current state of the process is saved, a new signal mask is calculated (as described below),

and the signal handler is invoked. The call to the handler is arranged so that if the signal handlingroutine

returns normally, the process resumes execution in the same context as before the signal’s delivery. If the

process wishes to resume in a different context, it must arrange to restore the previous context itself.

When a signal is delivered to a process, a new signal mask is installed for the duration of the process’ signal

handler (or until a sigblock() or sigsetmask() call is made). This mask is formed by taking the

current signal mask, computing the bit-wise inclusive OR with the value of vec.sv_mask (see below) from

the most recent call to sigvector() for the signal to be delivered, and, unless the SV_RESETHAND

ﬂag is set (see below), setting the bit corresponding to the signal being delivered. When the user’s signal

handler returns normally, the original mask is restored.

sigvector() assigns a handler for the signal speciﬁed by sig. vec and ovec are pointers to sigvec struc-

tures that include the following elements:

void (*sv_handler)();

long

sv_mask;

long

sv_ﬂags;

If vec is non-zero, it speciﬁes a handler routine (sv_handler), a mask (sv_mask) that the system should use

when delivering the speciﬁed signal, and a set of ﬂags (sv_ﬂags) that modify the delivery of the signal. If

ovec is non-zero, the previous handling information for the signal is returned to the user. If vec is zero, sig-

nal handling is unchanged. Thus, the call can be used to enquire about the current handling of a given sig-

nal. If vec and ovec point to the same structure, the value of vec is read prior to being overwritten.

The sv_ﬂags ﬁeld can be used to modify the receipt of signals. The following ﬂag bits are deﬁned:

SV_ONSTACK Use the sigspace() allocated space.

HP-UX Release 11i: December 2000 − 1 − Section 2−−369

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