The unw_is_signal_frame() routine returns a positive value if the current frame identified by cp is a signal frame, and a value of 0 otherwise. For the purpose of this discussion, a signal frame is a frame that was created in response to a potentially asynchronous interruption. For UNIX and UNIX-like platforms, such frames are normally created by the kernel when delivering a signal. In a kernel-environment, a signal frame might, for example, correspond to a frame created in response to a device interrupt.
Signal frames are somewhat unusual because the asynchronous nature of the events that create them require storing the contents of registers that are normally treated as scratch (``caller-saved'') registers.
On successful completion, unw_is_signal_frame() returns a positive value if the current frame is a signal frame, or 0 if it is not. Otherwise, a negative value of one of the error-codes below is returned.
THREAD AND SIGNAL SAFETY
unw_is_signal_frame() is thread-safe as well as safe to use from a signal handler.
Libunwind is unable to determine whether or not the current frame is a signal frame.