@signal

Sets the error handler for signal sig.

The signal handler can be set so that default handling will occur, signal is ignored, or an user-defined function is called.

When signal handler is set to a function and a signal occurs, it is implementation defined whether @signal (sig, SIG_DFL) will be executed immediately before the start of signal handler. Also, the implementation can prevent some implementation-defined set af signals from occurring while the signal handler runs.

If the user defined function returns when handling FPE, ILL or SEGV, the behavior is undefined. In most implementations the program terminates.

If the signal handler is called as a result of abort or raise, the behavior is undefined if any of the following requirements is not followed:

• the signal handler calls raise.
• the signal handler refers to an object of static storage duration which is not declared

  as volatile sig_atomic_t.

• the signal handler calls any function within the standard library, except abort,

  _Exit, or @signal with the first argument not being the number of the

  signal currently handled.