1sigchain API 2============ 3 4Code often wants to set a signal handler to clean up temporary files or 5other work-in-progress when we die unexpectedly. For multiple pieces of 6code to do this without conflicting, each piece of code must remember 7the old value of the handler and restore it either when: 8 9 1. The work-in-progress is finished, and the handler is no longer 10 necessary. The handler should revert to the original behavior 11 (either another handler, SIG_DFL, or SIG_IGN). 12 13 2. The signal is received. We should then do our cleanup, then chain 14 to the next handler (or die if it is SIG_DFL). 15 16Sigchain is a tiny library for keeping a stack of handlers. Your handler 17and installation code should look something like: 18 19------------------------------------------ 20 void clean_foo_on_signal(int sig) 21 { 22 clean_foo(); 23 sigchain_pop(sig); 24 raise(sig); 25 } 26 27 void other_func() 28 { 29 sigchain_push_common(clean_foo_on_signal); 30 mess_up_foo(); 31 clean_foo(); 32 } 33------------------------------------------ 34 35Handlers are given the typedef of sigchain_fun. This is the same type 36that is given to signal() or sigaction(). It is perfectly reasonable to 37push SIG_DFL or SIG_IGN onto the stack. 38 39You can sigchain_push and sigchain_pop individual signals. For 40convenience, sigchain_push_common will push the handler onto the stack 41for many common signals.