Petri: yes, that what I was suggesting.

Charles-François: I'm certainly open to alternatives. Unless I've overlooked something though, the problem is that no workaround is possible at the moment. BTW this came up in the context of a customer script for the software I work on, so it's not just a theoretical problem - at least, not for me. :-)

I guess another solution would be methods to save and restore the native signal handers, e.g. savesignal(signum) & restoresignal(signum). That wouldn't entirely solve the problem - if someone called setsignal() before calling savesignal(), they'd end up in the same situation - but it would at least permit a workaround.