sigemptysetactsamask

sigemptysetactsamask is not a standard function or macro in POSIX or Linux. It appears to be a concatenation of two separate concepts used together in signal handling: the function sigemptyset and the sa_mask field of struct sigaction. When encountered as a term, it usually signals that a programmer intends to initialize a signal set to empty and to use that set as the mask that controls which signals are blocked during the execution of a signal handler.

sigemptyset is a library function that initializes a signal set to be empty. Its typical purpose is to prepare a sigset_t object so that signals can then be selectively added to the set with sigaddset or sigdelset. The function has the prototype int sigemptyset(sigset_t *set); and on success, the set contains no signals.

In the context of signal handling, sa_mask is a field of the struct sigaction used to specify a signal mask that should be added to the process’s signal mask while the signal handler runs. The signals listed in sa_mask are blocked for the duration of the handler, in addition to the signal that triggered the handler. Initializing sa_mask with sigemptyset ensures that no additional signals are blocked during the handler.

Common usage patterns include setting up a signal handler with an empty sa_mask to avoid blocking other signals, or building a populated mask via sigemptyset followed by sigaddset and applying it with sigaction or sigprocmask. If you encounter the term sigemptysetactsamask in code, it is best read as a reference to using sigemptyset in conjunction with a handler’s sa_mask, rather than as a single API. For precise behavior, consult the POSIX sigemptyset, sigaction, and sigprocmask documentation.