---
name: "ACE_Sig_Handler"
section: "3"
platform: "linux"
package: "libace-doc"
version: "5.0.7-4"
release: "Debian 2.2 (Potato)"
platforms: ["linux"]
url: "https://new.carta.tech/ACE_Sig_Handler"
---

# ACE\_Sig\_Handler(3)

This is the main dispatcher of signals for ACE. It improves the existing UNIX signal handling mechanism by allowing C++ objects to handle signals in a way that avoids the use of global/static variables and functions.

## NAME

ACE\_Sig\_Handler -  This is the main dispatcher of signals for ACE.  It improves the existing UNIX signal handling mechanism by allowing C++ objects to handle signals in a way that avoids the use of global/static variables and functions.

## SYNOPSIS

```
#include <ace/Signal.h>
class ACE_Sig_Handler
{
  public:
    ACE_Sig_Handler (void);
    virtual ~ACE_Sig_Handler (void);
    virtual int register_handler (
        int signum,
        ACE_Event_Handler *new_sh,
        ACE_Sig_Action *new_disp = 0,
        ACE_Event_Handler **old_sh = 0,
        ACE_Sig_Action *old_disp = 0
        );
    virtual int remove_handler (
        int signum,
        ACE_Sig_Action *new_disp = 0,
        ACE_Sig_Action *old_disp = 0,
        int sigkey = -1
        );
    static int sig_pending (void);
    static void sig_pending (int);
    virtual ACE_Event_Handler *handler (int signum);
    virtual ACE_Event_Handler *handler (
        int signum,
        ACE_Event_Handler *
        );
    static void dispatch (int, siginfo_t *, ucontext_t *);
    void dump (void) const;
    ACE_ALLOC_HOOK_DECLARE;
  protected:
    static ACE_Event_Handler *handler_i (
        int signum,
        ACE_Event_Handler *
        );
    static int register_handler_i (
        int signum,
        ACE_Event_Handler *new_sh,
        ACE_Sig_Action *new_disp = 0,
        ACE_Event_Handler **old_sh = 0,
        ACE_Sig_Action *old_disp = 0
        );
    static int in_range (int signum);
    static sig_atomic_t sig_pending_;
  private:
    static ACE_Event_Handler *signal_handlers_[ACE_NSIG];
};
```

## DESCRIPTION

Using this class a program can register an ACE\_Event\_Handler with the ACE\_Sig\_Handler in order to handle a designated signum.  When a signal occurs that corresponds to this signum, the handle\_signal method of the registered ACE\_Event\_Handler is invoked automatically.

## Registration and removal methods.

```
virtual int register_handler (
    int signum,
    ACE_Event_Handler *new_sh,
    ACE_Sig_Action *new_disp = 0,
    ACE_Event_Handler **old_sh = 0,
    ACE_Sig_Action *old_disp = 0
    );
```

Add a new ACE\_Event\_Handler and a new sigaction associated with signum.  Passes back the existing ACE\_Event\_Handler and its sigaction if pointers are non-zero.  Returns -1 on failure and = 0 on success.

```
virtual int remove_handler (
    int signum,
    ACE_Sig_Action *new_disp = 0,
    ACE_Sig_Action *old_disp = 0,
    int sigkey = -1
    );
```

Remove the ACE\_Event\_Handler currently associated with signum.  sigkey is ignored in this implementation since there is only one instance of a signal handler.  Install the new disposition (if given) and return the previous disposition (if desired by the caller).  Returns 0 on success and -1 if signum is invalid.

Set/get signal status.

```
static int sig_pending (void);
```

True if there is a pending signal.

```
static void sig_pending (int);
```

Reset the value of sig\_pending\_ so that no signal is pending.

## Set/get the handler associated with a particular signal.

```
virtual ACE_Event_Handler *handler (int signum);
```

Return the ACE\_Sig\_Handler associated with signum.

```
virtual ACE_Event_Handler *handler (int signum, ACE_Event_Handler *);
```

Set a new ACE\_Event\_Handler that is associated with signum. Return the existing handler.

```
static void dispatch (int, siginfo_t *, ucontext_t *);
```

Callback routine registered with [sigaction(2)](/sigaction/2.md) that dispatches the handle\_signal method of the appropriate pre-registered ACE\_Event\_Handler.

```
void dump (void) const;
```

Dump the state of an object.

```
ACE_ALLOC_HOOK_DECLARE;
```

Declare the dynamic allocation hooks.

## These methods and data members are shared by derived classes.

```
static ACE_Event_Handler *handler_i (int signum, ACE_Event_Handler *);
```

Set a new ACE\_Event\_Handler that is associated with signum. Return the existing handler.  Does not acquire any locks so that it can be called from a signal handler, such as dispatch.

```
static int register_handler_i (
    int signum,
    ACE_Event_Handler *new_sh,
    ACE_Sig_Action *new_disp = 0,
    ACE_Event_Handler **old_sh = 0,
    ACE_Sig_Action *old_disp = 0
    );
```

This implementation method is called by register\_handler and dispatch.  It doesn't do any locking so that it can be called within a signal handler, such as dispatch.  It adds a new ACE\_Event\_Handler and a new sigaction associated with signum. Passes back the existing ACE\_Event\_Handler and its sigaction if pointers are non-zero.  Returns -1 on failure and = 0 on success.

```
static int in_range (int signum);
```

Check whether the SIGNUM is within the legal range of signals.

```
static sig_atomic_t sig_pending_;
```

Keeps track of whether a signal is pending.

## AUTHOR

Doug Schmidt

## LIBRARY

ace