On platforms where it is necessary (POSIX), installs, and potentially enables, the global signal handlers for the signals specified by guarded. Each signal installed is threadsafe reference counted, so this is safe to call from multiple threads or instantiate multiple times. It is also guaranteed safe to call from within static data init or deinit, so a very common use case is simply to place an instance into global static data. This ensures that dynamically loaded and unloaded shared objects compose signal guards appropriately.
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On platforms where it is necessary (POSIX), installs, and potentially enables, the global signal handlers for the signals specified by guarded. Each signal installed is threadsafe reference counted, so this is safe to call from multiple threads or instantiate multiple times. It is also guaranteed safe to call from within static data init or deinit, so a very common use case is simply to place an instance into global static data. This ensures that dynamically loaded and unloaded shared objects compose signal guards appropriately.
On platforms with better than POSIX global signal support, this class does nothing.
POSIX only
Any existing global signal handlers are replaced with a filtering signal handler, which checks if the current kernel thread has installed a signal guard, and if so executes the guard. If no signal guard has been installed for the current kernel thread, global signal continuation handlers are executed. If none claims the signal, the previously installed signal handler is called.
After the new signal handlers have been installed, the guarded signals are globally enabled for all threads of execution. Be aware that the handlers are installed with SA_NODEFER to avoid the need to perform an expensive syscall when a signal is handled. However this may also produce surprise e.g. infinite loops.
- Warning
- This class is threadsafe with respect to other concurrent executions of itself, but is NOT threadsafe with respect to other code modifying the global signal handlers. It is NOT async signal safe.
1.9.8