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Junio C Hamano982eb112010-11-18 00:53:09[diff] [blame]551</head>
552<body>
553<div id="header">
554<h1>sigchain API</h1>
555</div>
Junio C Hamano7bd050f2011-09-22 06:32:22[diff] [blame]556<div id="content">
Junio C Hamano982eb112010-11-18 00:53:09[diff] [blame]557<div id="preamble">
558<div class="sectionbody">
559<div class="paragraph"><p>Code often wants to set a signal handler to clean up temporary files or
560other work-in-progress when we die unexpectedly. For multiple pieces of
561code to do this without conflicting, each piece of code must remember
562the old value of the handler and restore it either when:</p></div>
563<div class="olist arabic"><ol class="arabic">
564<li>
565<p>
566The work-in-progress is finished, and the handler is no longer
567 necessary. The handler should revert to the original behavior
568 (either another handler, SIG_DFL, or SIG_IGN).
569</p>
570</li>
571<li>
572<p>
573The signal is received. We should then do our cleanup, then chain
574 to the next handler (or die if it is SIG_DFL).
575</p>
576</li>
577</ol></div>
578<div class="paragraph"><p>Sigchain is a tiny library for keeping a stack of handlers. Your handler
579and installation code should look something like:</p></div>
580<div class="listingblock">
581<div class="content">
582<pre><tt> void clean_foo_on_signal(int sig)
583 {
584 clean_foo();
585 sigchain_pop(sig);
586 raise(sig);
587 }
588
589 void other_func()
590 {
591 sigchain_push_common(clean_foo_on_signal);
592 mess_up_foo();
593 clean_foo();
594 }</tt></pre>
595</div></div>
Junio C Hamano7165bf72011-01-04 22:06:18[diff] [blame]596<div class="paragraph"><p>Handlers are given the typedef of sigchain_fun. This is the same type
Junio C Hamano982eb112010-11-18 00:53:09[diff] [blame]597that is given to signal() or sigaction(). It is perfectly reasonable to
598push SIG_DFL or SIG_IGN onto the stack.</p></div>
599<div class="paragraph"><p>You can sigchain_push and sigchain_pop individual signals. For
600convenience, sigchain_push_common will push the handler onto the stack
601for many common signals.</p></div>
602</div>
603</div>
Junio C Hamano7bd050f2011-09-22 06:32:22[diff] [blame]604</div>
605<div id="footnotes"><hr /></div>
Junio C Hamano982eb112010-11-18 00:53:09[diff] [blame]606<div id="footer">
607<div id="footer-text">
Junio C Hamano02194af2011-11-17 20:33:59[diff] [blame]608Last updated 2011-11-15 13:45:02 PDT
Junio C Hamano982eb112010-11-18 00:53:09[diff] [blame]609</div>
610</div>
611</body>
612</html>