Signal Class Reference

#include <evo/process.h>

Detailed Description

Process signal handling.

• This works with Linux/Unix signals as well as Windows signals (which are more limited)
• Caution: Signal handlers should only be set in the main thread of a process, i.e. in main()
• Caution: Signal handlers are sensitive to race conditions and should be minimal, and should not modify errno – especially in Linux/Unix
  • Ideally for best safety, limit signal handlers to setting status variable (even better with Atomic)

Example

Example using Signal::Main helper for a common case:

#include <evo/process.h>

static void on_shutdown(Signal::SigNumType, Signal::Type) {
    // shutdown code goes here
}

int main() {
    // Setup shutdown handler and call Signal::shutdown_sync() from destructor
    Signal::Main signal_main(on_shutdown);

    // main code goes here

    return 0;
}

Here's the same code without the helper:

#include <evo/process.h>

static void on_shutdown(Signal::SigNumType, Signal::Type) {
    // shutdown code goes here
}

int main() {
    Signal::set_on_shutdown(on_shutdown);

    // main code goes here

    // Required for Windows
    Signal::shutdown_sync();
    return 0;
}

Classes
struct	Main
	Helper for common shutdown signal handling in program main(). More...
struct	MainServer
	Helper for common server shutdown signal handling in program main(). More...

Public Types
enum	Action { aDEFAULT, aIGNORE }
	Signal handling action. More...
typedef void(*	Handler) (SigNumType, Type)
	Signal handler function type More...
typedef void(*	OnShutdown) (SigNumType, Type)
	General shutdown handler type. More...
typedef int	SigNumType
	Signal number value type. More...
enum	Type {   tUNKNOWN = 0, tINTERRUPT, tTERMINATE, tPIPE,   tCHILD, tHUP, tUSER1, tUSER2,   tWIN_BREAK, tWIN_CLOSE, tWIN_LOGOFF, tWIN_SHUTDOWN }
	Signal type. More...

Static Public Member Functions
static bool	send_signal (ProcessId pid, Type signal)
	Send signal to current process. More...
static bool	set_handler (Type type, Action action)
	Set signal handling option. More...
static bool	set_handler (Type type, Handler handler)
	Set signal handler. More...
static bool	set_on_shutdown (OnShutdown on_shutdown)
	Set shutdown handler. More...
static void	shutdown_sync ()
	Sync shutdown with signal handler. More...

Member Typedef Documentation

Handler

typedef void(* Handler) (SigNumType, Type)

Signal handler function type

OnShutdown

typedef void(* OnShutdown) (SigNumType, Type)

General shutdown handler type.

SigNumType

typedef int SigNumType

Signal number value type.

Member Enumeration Documentation

Action

enum Action

Signal handling action.

Enumerator
aDEFAULT	Use default handler, i.e. remove user handler.
aIGNORE	Ignore signal.

Type

enum Type

Signal type.

Enumerator
tUNKNOWN	Unknown signal type (used internally)
tINTERRUPT	Interrupted by Control-C (SIGINT) [Portable: Linux/Unix/Windows].
tTERMINATE	General terminate (SIGTERM) [Portable: Linux/Unix/Windows].
tPIPE	Write on broken pipe (SIGPIPE) [Linux/Unix].
tCHILD	Child process terminated (SIGCHLD), ignored by default [Linux/Unix].
tHUP	Terminal hangup, or daemon reload (SIGHUP) [Linux/Unix].
tUSER1	User defined signal 1 (SIGUSR1) [Linux/Unix].
tUSER2	User defined signal 2 (SIGUSR2) [Linux/Unix].
tWIN_BREAK	Control-Break (CTRL_BREAK_EVENT) [Windows].
tWIN_CLOSE	Process closed by user (CTRL_CLOSE_EVENT) [Windows].
tWIN_LOGOFF	User logging off, though which user is undefined (CTRL_LOGOFF_EVENT) [Windows, services only].
tWIN_SHUTDOWN	System shutting down (CTRL_SHUTDOWN_EVENT) [Windows, services only].

Member Function Documentation

send_signal()

static bool send_signal ( ProcessId  pid, Type  signal  )

inlinestatic

Send signal to current process.

Parameters

pid	Process ID or process group ID to send to
signal	Signal type to send

set_handler() [1/2]

static bool set_handler ( Type  type, Action  action  )

inlinestatic

Set signal handling option.

Parameters

type	Signal type
action	Action for signal

Returns

Whether successful, false if action couldn't be set

set_handler() [2/2]

static bool set_handler ( Type  type, Handler  handler  )

inlinestatic

Set signal handler.

Parameters

type	Signal type
handler	Handler for signal type, NULL to make sure main handler is installed without setting a user defined handler

Returns

Whether successful, false if action couldn't be set

set_on_shutdown()

static bool set_on_shutdown ( OnShutdown  on_shutdown )

inlinestatic

Set shutdown handler.

• This sets a general shutdown handler that is called on tINTERRUPT or tTERMINATE signals
• When this is set, shutdown_sync() should be called by main() right before it returns – this is required for graceful shutdown to work correctly in Windows
• Other handlers that were set via set_handler() are called before on_shutdown

shutdown_sync()

static void shutdown_sync ( )

inlinestatic

Sync shutdown with signal handler.

• This should be called right before main() exits, to notify that the process has shut down
• Windows signal handlers work differently and run in another thread, and this notifies that thread that shutdown is complete so it may finish and kill the process
• This is a no-op if a shutdown handler wasn't set, and is always a no-op in Linux/Unix

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The documentation for this class was generated from the following file:

• evo/process.h