C++ In a Nutshell

Name

signal function — Sets a signal handler

Synopsis

void (*signal(int sig, void (*func)(int)))(int);

The signal function controls the program’s behavior when a signal is delivered to the program. The first parameter (sig) is the signal number. The second parameter (func) is the function to call when signal sig is delivered.

The func parameter can also be one of the special values SIG_DFL or SIG_IGN. Use SIG_DFL to get the default behavior; use SIG_IGN to ignore a signal.

The default behavior for a signal is implementation-defined, but it usually results in the termination of the program. The signal handler must not use any C++ features (such as throwing an exception), or the results will be implementation-defined. The function must have "C" linkage.

If the func parameter is a function pointer, that function is called when signal sig is delivered. Unless the signal is delivered by calling abort or raise, the function is highly restricted in what it can do:

• The handler must not call any function in the standard library except signal, and the first parameter must be sig.

• The handler must not refer to any variable with static storage except it can assign a value to a variable of type volatile sig_atomic_t.

• If the signal is the result of a computational error such as SIGFPE, the signal handler must not return, but should call abort or exit. (Yes, this item contradicts the first item.)

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