| Junio C Hamano | 982eb11 | 2010-11-18 00:53:09 | [diff] [blame] | 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" |
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| 383 | </style> |
| 384 | </head> |
| 385 | <body> |
| 386 | <div id="header"> |
| 387 | <h1>sigchain API</h1> |
| 388 | </div> |
| 389 | <div id="preamble"> |
| 390 | <div class="sectionbody"> |
| 391 | <div class="paragraph"><p>Code often wants to set a signal handler to clean up temporary files or |
| 392 | other work-in-progress when we die unexpectedly. For multiple pieces of |
| 393 | code to do this without conflicting, each piece of code must remember |
| 394 | the old value of the handler and restore it either when:</p></div> |
| 395 | <div class="olist arabic"><ol class="arabic"> |
| 396 | <li> |
| 397 | <p> |
| 398 | The work-in-progress is finished, and the handler is no longer |
| 399 | necessary. The handler should revert to the original behavior |
| 400 | (either another handler, SIG_DFL, or SIG_IGN). |
| 401 | </p> |
| 402 | </li> |
| 403 | <li> |
| 404 | <p> |
| 405 | The signal is received. We should then do our cleanup, then chain |
| 406 | to the next handler (or die if it is SIG_DFL). |
| 407 | </p> |
| 408 | </li> |
| 409 | </ol></div> |
| 410 | <div class="paragraph"><p>Sigchain is a tiny library for keeping a stack of handlers. Your handler |
| 411 | and installation code should look something like:</p></div> |
| 412 | <div class="listingblock"> |
| 413 | <div class="content"> |
| 414 | <pre><tt> void clean_foo_on_signal(int sig) |
| 415 | { |
| 416 | clean_foo(); |
| 417 | sigchain_pop(sig); |
| 418 | raise(sig); |
| 419 | } |
| 420 | |
| 421 | void other_func() |
| 422 | { |
| 423 | sigchain_push_common(clean_foo_on_signal); |
| 424 | mess_up_foo(); |
| 425 | clean_foo(); |
| 426 | }</tt></pre> |
| 427 | </div></div> |
| Junio C Hamano | 7165bf7 | 2011-01-04 22:06:18 | [diff] [blame^] | 428 | <div class="paragraph"><p>Handlers are given the typedef of sigchain_fun. This is the same type |
| Junio C Hamano | 982eb11 | 2010-11-18 00:53:09 | [diff] [blame] | 429 | that is given to signal() or sigaction(). It is perfectly reasonable to |
| 430 | push SIG_DFL or SIG_IGN onto the stack.</p></div> |
| 431 | <div class="paragraph"><p>You can sigchain_push and sigchain_pop individual signals. For |
| 432 | convenience, sigchain_push_common will push the handler onto the stack |
| 433 | for many common signals.</p></div> |
| 434 | </div> |
| 435 | </div> |
| 436 | <div id="footer"> |
| 437 | <div id="footer-text"> |
| Junio C Hamano | 7165bf7 | 2011-01-04 22:06:18 | [diff] [blame^] | 438 | Last updated 2011-01-04 22:05:44 UTC |
| Junio C Hamano | 982eb11 | 2010-11-18 00:53:09 | [diff] [blame] | 439 | </div> |
| 440 | </div> |
| 441 | </body> |
| 442 | </html> |
