blocks|key|1351885|text|Symbian用longjmp()实现了它的Leave机制，这是你需要做的所有事情的一个很好的演练。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1351886|Symbian有一个全局的“清理堆栈”，如果发生跳跃，你可以推送和弹出你想要清理的东西。这是在抛出C%2B%2B异常时C%2B%2B编译器自动展开堆栈的手动替代方法。|1351887|Symbian有“陷阱工具”可以跳出来；它们可以嵌套在一起。|1351888|(塞班最近在C%2B%2B异常方面重新实现了它，但接口保持不变)。|1351889|总而言之，我认为适当的C%2B%2B异常不太容易出现编码错误，而且比使用自己的C等效物要快得多。|1351890|(例如，当异常不被抛出时，现代C%2B%2B编译器非常擅长“零开销”异常；longjmp()必须存储所有寄存器的状态，即使后来没有进行跳转，因此从根本上讲永远不会像异常那样快。)|1351891|使用C%2B%2B作为更好的C语言，因为您只采用异常和RAII，如果使用longjmp()进行异常模拟对您很有吸引力，这将是一个很好的方法。|1351892|entityMap^0|8|9|M|5|0|0|0|0|0|X|9|0|W|9|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|Z|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|10|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|11|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|S|$]]

Symbian implemented it's <code>Leave</code> mechanism in terms of <code>longjmp()</code> and this serves as a good walk through of all the things you need to do.

Symbian has a global 'cleanup stack' that you push and pop things you want cleaned up should an jump happened. This is the manual alternative to the automatic stack unwinding that a C++ compiler does when a C++ exception is thrown.

Symbian had 'trap harnesses' that it would jump out to; these could be nested.

(Symbian more recently reimplemented it in terms of C++ exceptions, but the interface remains unchanged).

All together, I think that proper C++ exceptions are less prone to coding errors and much faster than rolling your own C equivalent.

(Modern C++ compilers are very good at 'zero overhead' exceptions when they are not thrown, for example; <code>longjmp()</code> has to store the state of all the registers and such even when the jump is not later taken, so can fundamentally never be as fast as exceptions.)

Using C++ as a better C, where you only adopt exceptions and RAII, would be a good route should using <code>longjmp()</code> for exception emulation be tempting to you.

blocks|key|1567417|text|到目前为止，异常是一种更好的通用机制，但在C过去的黑暗时代，我编写了一个包含命令shell的处理器仿真器。用于设置中断处理的for+/longjmp的shell+(即，处理器正在运行，用户按break/ctrl-c，代码将SIGINT和longjmps捕获回shell)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1567418|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Exceptions are by far a better general mechanism, but in the deep dark days of C past, I wrote a processor emulator that included a command shell. The shell used to setjmp/longjmp for interrupt handling (ie, the processor is running and the user hits break/ctrl-c, the code traps SIGINT and longjmps back to the shell).

blocks|key|1567446|text|请看下面的示例/教程：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1567447|http://www.di.unipi.it/~nids/docs/longjump_try_trow_catch.html|offset|length|1567448|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1Q|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]|$1|F|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|C]]]]

Have a look at this example/tutorial: 
<a href="http://www.di.unipi.it/~nids/docs/longjump_try_trow_catch.html" rel="noreferrer">http://www.di.unipi.it/~nids/docs/longjump_try_trow_catch.html</a>

blocks|key|1567529|text|如果您担心资源清理，那么您必须认真考虑longjmp()和setjmp()是否是一个好主意。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1567530|如果您设计您的资源分配系统，以便您实际上可以准确地清理，那么它是可以的-但是，如果您的代码所使用的标准库实际上分配了必须释放的资源，那么这种设计往往是棘手的，而且通常是不完整的。它需要格外小心，而且因为它并不完全可靠，所以不适合可能需要多次使用setjmp()/longjmp()调用(它们会泄漏、扩展并最终导致问题)的长时间运行的系统。|1567531|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If you are worried about resource cleanup, you have to seriously wonder whether longjmp() and setjmp() are a good idea.

If you design your resource allocation system so that you can in fact clean up accurately, then it is OK - but that design tends to be tricky, and typically incomplete if, in fact, the standard libraries that your code uses themselves allocate resources that must be released. It requires extraordinary care, and because it is not wholly reliable, it is not suitable for long-running systems that might need to survive multiple uses of the setjmp()/longjmp() calls (they'll leak, expand, and eventually cause problems).

blocks|key|1567612|text|我已经相当整洁地使用了setjmp/longjmp，以避免在回调中使用，而不必通过各种其他库级别进行协商。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1567613|在这种情况下(如果我没记错的话)，yacc生成的解析器中的代码可以检测到(非语法的)问题，并希望放弃解析，但向所有yacc生成的代码另一端的调用者返回一个相当有用的错误报告。另一个示例是在从Expat解析器调用的回调中。在每种情况下，都有其他方法来做到这一点，但它们似乎比简单地以这种方式摆脱困境更为繁琐和晦涩。|1567614|但是，正如其他答案所指出的那样，有必要小心清理，并且要非常仔细地确保longjmp代码仅在setjmp动态保护的区域范围内可调用。|1567615|是在多线程编程的环境下做的吗？我相信这不是不可能的，但是哦:现在就拿出你的家庭用的阿司匹林吧。将setjmp/longjmp对尽可能地放在一起可能是明智的。只要匹配的setjmp/longjmp对在同一个线程中，我希望您可以接受，但是...在外面要当心。|1567616|entityMap^0|B|6|I|7|0|0|Y|7|19|6|0|1C|6|1J|7|2B|6|2I|7|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|S|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|L|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|M|$]]

I've used <code>setjmp</code>/<code>longjmp</code> reasonably tidily, to escape from within a callback, without having to negotiate my way up through various other library levels.

That case (if I recall correctly) was where a code within a yacc-generated parser could detect a (non-syntactical) problem, and wanted to abandon the parse but give a reasonably useful error report back to the caller on the other side of all the yacc-generated code. Another example was within a callback called from an Expat parser. In each case, there were other ways of doing this, but they seemed more cumbersome and obscure than simply bailing out in this way.

As other answers have pointed out, though, it's necessary to be careful about clean-up, and very thoughtful about making sure that the <code>longjmp</code> code is callable only within the scope of the region dynamically protected by the <code>setjmp</code>.

Doing it in the context of multi-threaded programming? I'm sure that's not impossible, but Oooh: get out your family-pack of aspirin now. It's probably wise to keep the <code>setjmp</code>/<code>longjmp</code> pairs as close together as possible. As long as a matching <code>setjmp</code>/<code>longjmp</code> pair are within the same thread, I expect you'll be OK, but ... be careful out there.

I have to use C for one project and I am thinking of using <code>longjmp/setjmp</code> for error handling as I think it will be much easier to handle error in one central place than return codes. I would appreciate if there are some leads on how to do this.

I am particularly concerned with resource cleanup being correctly done if any such error occurs. 

Also how do I handle errors that result in multi-threaded programs using them?

Even better, is there some C library that already exists for error/exception handling?

What are some "good" ways to use longjmp/setjmp for C error handling?

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我不得不在一个项目中使用C，我正在考虑使用longjmp/setjmp进行错误处理，因为我认为在一个中心位置处理错误将比返回代码容易得多。如果有一些关于如何做到这一点的线索，我将不胜感激。我特别关心的是，如果发生任何这样的错误，资源清理是否被正确完成。另外，如何处理导致多线程程序使用它们的错误？更好的是，是否已经存在一...

问使用longjmp/setjmp进行C错误处理的一些“好”方法是什么？
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