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1#ifndef SIGCHAIN_H
2#define SIGCHAIN_H
3
4/**
5 * Code often wants to set a signal handler to clean up temporary files or
6 * other work-in-progress when we die unexpectedly. For multiple pieces of
7 * code to do this without conflicting, each piece of code must remember
8 * the old value of the handler and restore it either when:
9 *
10 * 1. The work-in-progress is finished, and the handler is no longer
11 * necessary. The handler should revert to the original behavior
12 * (either another handler, SIG_DFL, or SIG_IGN).
13 *
14 * 2. The signal is received. We should then do our cleanup, then chain
15 * to the next handler (or die if it is SIG_DFL).
16 *
17 * Sigchain is a tiny library for keeping a stack of handlers. Your handler
18 * and installation code should look something like:
19 *
20 * ------------------------------------------
21 * void clean_foo_on_signal(int sig)
22 * {
23 * clean_foo();
24 * sigchain_pop(sig);
25 * raise(sig);
26 * }
27 *
28 * void other_func()
29 * {
30 * sigchain_push_common(clean_foo_on_signal);
31 * mess_up_foo();
32 * clean_foo();
33 * }
34 * ------------------------------------------
35 *
36 */
37
38/**
39 * Handlers are given the typedef of sigchain_fun. This is the same type
40 * that is given to signal() or sigaction(). It is perfectly reasonable to
41 * push SIG_DFL or SIG_IGN onto the stack.
42 */
43typedef void (*sigchain_fun)(int);
44
45/* You can sigchain_push and sigchain_pop individual signals. */
46int sigchain_push(int sig, sigchain_fun f);
47int sigchain_pop(int sig);
48
49/**
50 * push the handler onto the stack for the common signals:
51 * SIGINT, SIGHUP, SIGTERM, SIGQUIT and SIGPIPE.
52 */
53void sigchain_push_common(sigchain_fun f);
54
55void sigchain_pop_common(void);
56
57#endif /* SIGCHAIN_H */