sysv_signal - signal handling with System V semantics
#define _GNU_SOURCE /* See feature_test_macros(7) */
typedef void (*sighandler_t)(int);
However sysv_signal() provides the System V unreliable signal semantics, that is: a) the disposition of the signal is reset to the default when the handler is invoked; b) delivery of further instances of the signal is not blocked while the signal handler is executing; and c) if the handler interrupts (certain) blocking system calls, then the system call is not automatically restarted.
The sysv_signal() function returns the previous value of the signal handler, or SIG_ERR on error.
As for signal(2).
This function is nonstandard.
The use of
sighandler_t is a GNU extension; this type is defined only if the _GNU_SOURCE feature test macro is defined.
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