int pthread_sigmask(int how, const sigset_t *restrict
sigset_t *restrict oset);
int sigprocmask(int how, const sigset_t *restrict
sigset_t *restrict oset);
The pthread_sigmask() function shall examine or change (or both) the calling thread's signal mask, regardless of the number of threads in the process. The function shall be equivalent to sigprocmask(), without the restriction that the call be made in a single-threaded process.
In a single-threaded process, the sigprocmask() function shall examine or change (or both) the signal mask of the calling thread.
If the argument set is not a null pointer, it points to a set of signals to be used to change the currently blocked set.
The argument how indicates the way in which the set is changed, and the application shall ensure it consists of one of the following values:
If the argument oset is not a null pointer, the previous mask shall be stored in the location pointed to by oset. If set is a null pointer, the value of the argument how is not significant and the process' signal mask shall be unchanged; thus the call can be used to enquire about currently blocked signals.
If there are any pending unblocked signals after the call to sigprocmask(), at least one of those signals shall be delivered before the call to sigprocmask() returns.
It is not possible to block those signals which cannot be ignored. This shall be enforced by the system without causing an error to be indicated.
If any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are generated while they are blocked, the result is undefined, unless the signal was generated by the kill() function, the sigqueue() function, or the raise() function.
If sigprocmask() fails, the thread's signal mask shall not be changed.
The use of the sigprocmask() function is unspecified in a multi-threaded process.
Upon successful completion pthread_sigmask() shall return 0; otherwise, it shall return the corresponding error number.
Upon successful completion, sigprocmask() shall return 0; otherwise, -1 shall be returned, errno shall be set to indicate the error, and the process' signal mask shall be unchanged.
The pthread_sigmask() and sigprocmask() functions shall fail if:
The pthread_sigmask() function shall not return an error code of [EINTR].
The following sections are informative.
When a process' signal mask is changed in a signal-catching function that is installed by sigaction(), the restoration of the signal mask on return from the signal-catching function overrides that change (see sigaction()). If the signal-catching function was installed with signal(), it is unspecified whether this occurs.
See kill() for a discussion of the requirement on delivery of signals.
sigaction() , sigaddset() , sigdelset() , sigemptyset() , sigfillset() , sigismember() , sigpending() , sigqueue() , sigsuspend() , the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>