UT_Signal.h

Go to the documentation of this file.

/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        UT library (C++)
 *
 * COMMENTS:    Wrapper on signal handlers.
 *              By instantiating an object of this type, the signal
 *              handler is set to the desired value.  When this
 *              object is destructed, the signals are automatically
 *              returned to their previous values.
 *
 * NOTES:       Since the constructor/destructor handle installing
 *              and removal of the signals, this can even be used
 *              within a block of code to allow signals to be caught
 *              temporarily.
 *              When installing signals permanently, it is suggested
 *              that signal(2) still be used.  However, it is possible
 *              to use the static "override" method below.
 */

#ifndef __UT_Signal_h__
#define __UT_Signal_h__

#include "UT_API.h"

#include "UT_Array.h"

#include <signal.h>             // Get a list of signals for us please

#if defined(WIN32)
    // define all the signals not already defined by NT.
    // Removed two signals that conflicted with defined NT signals.
        // Reserved signal #'s on NT so far are: 2,4,8,11,15,21,22
    // Please note that addSignal will silently ignore any non-handled
    // windows handlers as the runtime library does parameter validation
    // and rejects them.
    #define     SIGHUP  1
    // WIN32:   SIGINT  2
    #define     SIGQUIT 3
    // WIN32:   SIGILL  4
    #define     SIGTRAP 5       // Unhandled
    #define     SIGEMT  7       // Unhandled
    // WIN32:   SIGFPE  8
    #define     SIGKILL 9       // Unhandled
    #define     SIGBUS  10      // Unhandled
    // WIN32:   SIGSEGV 11
    #define     SIGSYS  12      // Unhandled
    #define     SIGPIPE 13
    #define     SIGALRM 14      // Unhandled
    // WIN32:   SIGTERM 15
    #define     SIGUSR1 16      // Windows: IOINT?
    #define     SIGUSR2 17      // Windows: STOP?
                // do not use SIGCLD anymore! provided here for backwards
                // compatibility only!
    #define     SIGCLD  18      // Unhandled
                // SIGCCHLD is the new POSIX name for SIGCLD, use this instead
    #define     SIGCHLD 18      // Unhandled
    #define     SIGPWR  19      // Unhandled
    #define     SIGWINCH 20     // Unhandled
    // WIN32:   SIGBREAK 21
    // It's probably ok that SIGURG (urgent socket condition) is handled the
    // same as SIGBREAK since there's no such thing on NT
    #define     SIGURG  21
    // WIN32:   SIGABRT 22
    #define     SIGSTOP 23      // Unhandled
    #define     SIGTSTP 24      // Unhandled
    #define     SIGCONT 25      // Unhandled
    #define     SIGTTIN 26      // Unhandled
    #define     SIGTTOU 27      // Unhandled
    #define     SIGVTALRM 28    // Unhandled
    #define     SIGPROF 29      // Unhandled
    #define     SIGXCPU 30      // Unhandled
    #define     SIGXFSZ 31      // Unhandled
    #define     SIG32   32      // Unhandled
    // According to Irix it supports all signal numbers between 0 and 64
    // So all other signals should probably start at 65
    #define     SIGPOLL 65      // Unhandled

    #define sigset(a,b) signal(a,b)
#else

#if !defined(SIGEMT)
#if defined(SIGUNUSED)
#define SIGEMT SIGUNUSED
#else
#define SIGEMT SIGBUS
#endif
#endif

#if !defined(SIGSYS)
#if defined(SIGUNUSED)
#define SIGSYS SIGUNUSED
#else
#define SIGSYS SIGBUS
#endif
#endif

#endif

#define UT_MAX_SIGNALS  64      // Allow for POSIX standard

#if defined(LINUX) || defined(MBSD)
#define SUPPORTS_SIGINFO
#endif

class UT_API UTsignalHandlerArg
{
public:
    UTsignalHandlerArg(int signal_num)
        : mySignalNum(signal_num),
          myOpaqueCPUContext(0),
          myDepthFromSignalHandler(0)
    {}

    /// Increment the depth from the signal handler in the copy constructor.
    /// That way, as the signal handler argument is passed from the signal
    /// handler function to other functions, we'll know how far back up
    /// in the stack the original signal handler function is.
    UTsignalHandlerArg(const UTsignalHandlerArg &sig_arg)
        : mySignalNum(sig_arg.mySignalNum),
#ifdef SUPPORTS_SIGINFO
          mySignalInfo(sig_arg.mySignalInfo),
#endif
          myOpaqueCPUContext(sig_arg.myOpaqueCPUContext),
          myDepthFromSignalHandler(sig_arg.myDepthFromSignalHandler + 1)
    {}

    int getSignalNum() const { return mySignalNum; }

#ifdef SUPPORTS_SIGINFO
    void         setSignalInfo(siginfo_t *signal_info)
    {
        mySignalInfo = signal_info;
    }
    const siginfo_t *getSignalInfo() const { return mySignalInfo; }
#endif
    void         setSignalContext(void *opaque_cpu_context)
    {
        myOpaqueCPUContext = opaque_cpu_context;
    }
    const void      *getOpaqueCPUContext() const { return myOpaqueCPUContext; }

    int              getDepthFromSignalHandler() const
                                        { return myDepthFromSignalHandler; }

private:
    int          mySignalNum;
    void        *myOpaqueCPUContext;
    int          myDepthFromSignalHandler;
#ifdef SUPPORTS_SIGINFO
    siginfo_t   *mySignalInfo;
#endif
};


typedef void (*UTsigHandler)(UTsignalHandlerArg);

#if !defined(LINUX) && !defined(MBSD)
extern "C"
#endif
typedef void (*UToldStyleSigHandler)(int);

class UT_API UT_Signal
{
public:
    /// Catch a specified signal.  If signum <= 0, then all signals
    /// (except ABRT) are caught.  There are two styles of constructors.
    /// One takes an old-style signal handler that is needed so we can easily
    /// specify SIG_DFL, SIG_IGN, and SIG_ERR as the signal behaviours.  The
    /// other constructor takes our own data structure as an argument and is
    /// designed to support the SA_SIGINFO 3-argument style callback added in
    /// POSIX.1b.
    /// If ignore_prev is false, all other signal handlers for the raised
    /// signal will be called in the reverse order they were installed.
    /// Otherwise, only the last handler for this signal will be called.
    explicit UT_Signal(int signum=0, UToldStyleSigHandler handler = SIG_DFL,
                       bool ignore_prev=false);
    explicit UT_Signal(int signum, UTsigHandler handler,
                       bool ignore_prev=false);

    /// Catch a specified set of signals.  The first argument is an
    ///   array of signal numbers to catch.  The array should be
    ///   null terminated (since there is no signal 0)
    template <std::size_t Size>
    UT_Signal(const int (&signums)[Size], UToldStyleSigHandler handler = SIG_DFL,
              bool ignore_prev=false)
    {
        constructPriv(signums, Size, handler, ignore_prev);
    }
    template <std::size_t Size>
    UT_Signal(const int (&signums)[Size], UTsigHandler handler,
              bool ignore_prev=false)
    {
        constructPriv(signums, Size, handler, ignore_prev);
    }
    explicit UT_Signal(const UT_Array<int> &signums, UTsigHandler handler,
                bool ignore_prev = false);
    explicit UT_Signal(const UT_Array<int> &signums,
                UToldStyleSigHandler handler = SIG_DFL,
                bool ignore_prev = false);
    /// Destructing will restore the signals to their previous values.
    ~UT_Signal();

    /// The following method is made available to override the default
    /// handler without destructing the object.  For example, in the
    /// signal handler, you may want to ignore further signals of a certain
    /// type.  This method allows you to set the signals.  In fact, it
    /// simply calls sigaction() with the new handler.
    void        override(int signum, UToldStyleSigHandler,
                         bool ignore_prev=false);
    void        override(int signum, UTsigHandler,
                         bool ignore_prev=false);

    /// This disables the cant return behaviour used in UT_Signal. This
    /// behaviour will abort the application on behalf of the application
    /// itself for signals that it treats as cant return (i.e. SIGTERM). For
    /// some applications the application needs to control the full shutdown
    /// otherwise the application can end up erroring on exit.
    static void disableCantReturn(bool disable);

private:
    /// This class keeps track of a signal handler callback that is either
    /// an old-style callback (one that accepts an int, like SIG_DFL or
    /// SIG_IGN) or a new-style callback (one that accepts a UTsignalHandlerArg).
    class UT_API UT_ComboSignalHandler
    {
    public:
        UT_ComboSignalHandler();
        UT_ComboSignalHandler(UTsigHandler handler);
        UT_ComboSignalHandler(UToldStyleSigHandler handler);

        UT_ComboSignalHandler &operator=(UTsigHandler handler);
        UT_ComboSignalHandler &operator=(UToldStyleSigHandler handler);
        bool operator!=(UToldStyleSigHandler handler) const;

        bool isSet() const;
        void operator()(int signal_num,
#ifdef SUPPORTS_SIGINFO
                        siginfo_t *signal_info,
#endif
                        void *opaque_cpu_context) const;

    private:
        union
        {
            UTsigHandler         myNewStyle;
            UToldStyleSigHandler myOldStyle;
        } mySigHandler;
        bool myIsOldStyleSigHandler;
    };

    void                 constructPriv(int signum,
                                       UT_ComboSignalHandler handler,
                                       bool ignore_prev);
    void                 constructPriv(const int signums[],
                                        const std::size_t size,
                                       UT_ComboSignalHandler handler,
                                       bool ignore_prev);
    void                 addSignal(int signum, UT_ComboSignalHandler handler,
                                   bool ignore_prev);
    void                 removeSignal(int signum);
    void                 updateActuals();
    void                 overridePriv(int signum,
                                      UT_ComboSignalHandler handler,
                                      bool ignore_prev);

    static void          processSignal(int signal_num
#ifdef SUPPORTS_SIGINFO
                                       , siginfo_t *, void *
#endif
                                      );

    UT_ComboSignalHandler mySignals[UT_MAX_SIGNALS];
    bool                 myIgnorePrev[UT_MAX_SIGNALS];

    UT_Signal           *myNext, *myPrev;
};

#endif