crashzone.hxx

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#ifndef INCLUDED_COMPHELPER_CRASHZONE_H
#define INCLUDED_COMPHELPER_CRASHZONE_H

#include <sal/config.h>

#include <atomic>
#include <csignal>
#include <type_traits>

struct CrashWatchdogTimingsValues
{
    int mnDisableEntries;
    int const mnAbortAfter;
};

template <typename Dummy> class CrashZone
{
// gnEnterCount and gnLeaveCount are accessed both from multiple threads (cf.
// WatchdogThread::execute; so need to be of atomic type) and from signal handlers (cf.
// VCLExceptionSignal_impl; so need to be of lock-free atomic type).  sig_atomic_t is chosen as
// the underlying type under the assumption that it is most likely to lead to an atomic type
// that is actually lock-free.  However, gnEnterCount and gnLeaveCount are both monotonically
// increasing, so will eventually overflow, so the underlying type better be unsigned, which
// sig_atomic_t is not guaranteed to be:
#if !defined ARM32 || (defined ARM32 && defined __ARM_PCS_VFP)
    using AtomicCounter = std::atomic<std::make_unsigned_t<std::sig_atomic_t>>;
    static_assert(AtomicCounter::is_always_lock_free);
#else
    using AtomicCounter = volatile std::make_unsigned_t<std::sig_atomic_t>;
#endif

    static inline AtomicCounter gnEnterCount = 0;
    static inline AtomicCounter gnLeaveCount = 0;

public:
    CrashZone() { enter(); }
    ~CrashZone() { leave(); }
    static bool isInZone() { return gnEnterCount != gnLeaveCount; }
    static const AtomicCounter& enterCount() { return gnEnterCount; }
    // prefer creating instances to manually calling enter()/leave()
    static void enter() { gnEnterCount++; }
    static void leave() { gnLeaveCount++; }
    // these should be implemented for each specific zone if needed
    // static void hardDisable();
    // static const CrashWatchdogTimingsValues& getCrashWatchdogTimingsValues();
    // static void checkDebug(int nUnchanged, const CrashWatchdogTimingsValues& aTimingValues);
    // static const char* name();
};

#endif // INCLUDED_COMPHELPER_CRASHZONE_H

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