Signal Handling Action Definitions

The following table shows the initial state of the C signal values and their handling action definitions when SYSIFCOPT(*NOASYNCSIGNAL) is specified on the compilation command. SIG_DFL always percolates the condition to the handler. Resume indicates the exception is handled, and the application continues.

Table 15. Handling Action Definitions for Signal Values
Signal Value Initial State SIG_DFL SIG_IGN Return from Handler
SIGABRT1 SIG_DFL Percolate Ignore Resume
SIGALL2 SIG_DFL Percolate Ignore Resume
SIGFPE SIG_DFL Percolate Ignore3 Resume4
SIGILL SIG_DFL Percolate Ignore3 Resume4
SIGINT SIG_DFL Percolate Ignore Resume
SIGIO SIG_IGN Percolate Ignore Resume
SIGOTHER SIG_DFL Percolate Ignore3 Resume4
SIGSEGV SIG_DFL Percolate Ignore3 Resume4
SIGTERM SIG_DFL Percolate Ignore Resume
SIGUSR1 SIG_DFL Percolate Ignore Resume
SIGUSR2 SIG_DFL Percolate Ignore Resume
Note:
  • 1 Can only be signaled by the raise() function or the abort() function
  • 2 SIGALL cannot be signaled by the raise() function.
  • 3 If the value of the signal is SIGFPE, SIGILL or SIGSEGV the behavior is undefined.
  • 4 If the signal is hardware-generated, then the behavior undefined.

The following table shows the initial state of the C signal values and their handling action definitions when SYSIFCOPT(*ASYNCSIGNAL) is specified on the compilation command.

Table 16. Default Actions for Signal Values
Value Default Action Meaning
SIGABRT 2 Abnormal termination.
SIGFPE 2 Arithmetic exceptions that are not masked, such as overflow, division by zero, and incorrect operation.
SIGILL 2 Detection of an incorrect function image.
SIGINT 2 Interactive attention.
SIGSEGV 2 Incorrect access to storage.
SIGTERM 2 Termination request sent to the program.
SIGUSR1 2 Intended for use by user applications.
SIGUSR2 2 Intended for use by user applications.
SIGALRM 2 A timeout signal that is sent by alarm().
SIGHUP 2 A controlling terminal is hung up, or the controlling process ended.
SIGKILL 1 A termination signal that cannot be caught or ignored.
SIGPIPE 3 A write to a pipe that is not being read.
SIGQUIT 2 A quit signal for a terminal.
SIGCHLD 3 An ended or stopped child process. SIGCLD is an alias name for this signal.
SIGCONT 5 If stopped, continue.
SIGSTOP 4 A stop signal that cannot be caught or ignored.
SIGTSTP 4 A stop signal for a terminal.
SIGTTIN 4 A background process attempted to read from a controlling terminal.
SIGTTOU 4 A background process attempted to write to a controlling terminal.
SIGIO 3 Completion of input or output.
SIGURG 3 High bandwidth data is available at a socket.
SIGPOLL 2 Pollable event.
SIGBUS 2 Specification exception.
SIGPRE 2 Programming exception.
SIGSYS 2 Bad system call.
SIGTRAP 2 Trace or breakpoint trap.
SIGPROF 2 Profiling timer expired.
SIGVTALRM 2 Virtual timer expired.
SIGXCPU 2 Processor time limit exceeded.
SIGXFSZ 2 File size limit exceeded.
SIGDANGER 2 System crash is imminent.
SIGPCANCEL 2 Thread termination signal that cannot be caught or ignored.

Default Actions:

1
End the process immediately.
2
End the request.
3
Ignore the signal.
4
Stop the process.
5
Continue the process if it is currently stopped. Otherwise, ignore the signal.

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