technical/api-sigchain.html - pub/scm/git/git-htmldocs - Git at Google

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 <div id="header">
 <h1>sigchain API</h1>
 </div>
 <div id="content">
 <div id="preamble">
 <div class="sectionbody">
 <div class="paragraph"><p>Code often wants to set a signal handler to clean up temporary files or
 other work-in-progress when we die unexpectedly. For multiple pieces of
 code to do this without conflicting, each piece of code must remember
 the old value of the handler and restore it either when:</p></div>
 <div class="olist arabic"><ol class="arabic">
 <li>
 <p>
 The work-in-progress is finished, and the handler is no longer
      necessary. The handler should revert to the original behavior
      (either another handler, SIG_DFL, or SIG_IGN).
 </p>
 </li>
 <li>
 <p>
 The signal is received. We should then do our cleanup, then chain
      to the next handler (or die if it is SIG_DFL).
 </p>
 </li>
 </ol></div>
 <div class="paragraph"><p>Sigchain is a tiny library for keeping a stack of handlers. Your handler
 and installation code should look something like:</p></div>
 <div class="listingblock">
 <div class="content">
 <pre><code>  void clean_foo_on_signal(int sig)
   {
           clean_foo();
           sigchain_pop(sig);
           raise(sig);
   }

   void other_func()
   {
           sigchain_push_common(clean_foo_on_signal);
           mess_up_foo();
           clean_foo();
   }</code></pre>
 </div></div>
 <div class="paragraph"><p>Handlers are given the typedef of sigchain_fun. This is the same type
 that is given to signal() or sigaction(). It is perfectly reasonable to
 push SIG_DFL or SIG_IGN onto the stack.</p></div>
 <div class="paragraph"><p>You can sigchain_push and sigchain_pop individual signals. For
 convenience, sigchain_push_common will push the handler onto the stack
 for many common signals.</p></div>
 </div>
 </div>
 </div>
 <div id="footnotes"><hr /></div>
 <div id="footer">
 <div id="footer-text">
 Last updated
  2018-01-26 15:11:04 PST
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	</head>
	<body class="article">
	<div id="header">
	<h1>sigchain API</h1>
	</div>
	<div id="content">
	<div id="preamble">
	<div class="sectionbody">
	<div class="paragraph"><p>Code often wants to set a signal handler to clean up temporary files or
	other work-in-progress when we die unexpectedly. For multiple pieces of
	code to do this without conflicting, each piece of code must remember
	the old value of the handler and restore it either when:</p></div>
	<div class="olist arabic"><ol class="arabic">
	<li>
	<p>
	The work-in-progress is finished, and the handler is no longer
	necessary. The handler should revert to the original behavior
	(either another handler, SIG_DFL, or SIG_IGN).
	</p>
	</li>
	<li>
	<p>
	The signal is received. We should then do our cleanup, then chain
	to the next handler (or die if it is SIG_DFL).
	</p>
	</li>
	</ol></div>
	<div class="paragraph"><p>Sigchain is a tiny library for keeping a stack of handlers. Your handler
	and installation code should look something like:</p></div>
	<div class="listingblock">
	<div class="content">
	<pre><code> void clean_foo_on_signal(int sig)
	{
	clean_foo();
	sigchain_pop(sig);
	raise(sig);
	}

	void other_func()
	{
	sigchain_push_common(clean_foo_on_signal);
	mess_up_foo();
	clean_foo();
	}</code></pre>
	</div></div>
	<div class="paragraph"><p>Handlers are given the typedef of sigchain_fun. This is the same type
	that is given to signal() or sigaction(). It is perfectly reasonable to
	push SIG_DFL or SIG_IGN onto the stack.</p></div>
	<div class="paragraph"><p>You can sigchain_push and sigchain_pop individual signals. For
	convenience, sigchain_push_common will push the handler onto the stack
	for many common signals.</p></div>
	</div>
	</div>
	</div>
	<div id="footnotes"><hr /></div>
	<div id="footer">
	<div id="footer-text">
	Last updated
	2018-01-26 15:11:04 PST
	</div>
	</div>
	</body>
	</html>