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From: Jan Burse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Re: [Windows] Any way to distinguish ^C Induced EOF from ^Z EOF?
Date: Mon, 12 Mar 2012 20:16:12 +0100
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Xref: csiph.com comp.lang.java.programmer:12909

Arne Vajhøj schrieb:
> If a developer chose Java for a task that Java was not designed
> for and has never been prioritized since, then it is the
> developers faults not Java's fault.

Here is an example (although quite an artifical one)
which shows how this flaw can harm the end-user. Consider
this naive code:


    System.out.println("Do you want commit/rollback? (^D or ^Z/Enter)");
    String str=br.readLine();
    if (str=null) {
       commitTransaction();
    } else if ("".equals(str)) {
       rollbackTransaction();
    }

Now what do you expect a program to do after the prompt:

    Do you want commit/rollback? (^D or ^Z/Enter)

When the end-user presses ^C. Here is what happens on
the different platforms because of this flaw:

    Mac or Linux: Upon pressing ^C the standard interrupt
       handler will be invoked, which calls System.exit(),
       neither commit nor rollback is issued, depending
       on the database most likely the System.exit() will
       do a rollback.

    Windows: A race condition is induced. Upon pressing
       ^C two things will happen: The readLine() will
       return null and in the same time the standard
       interrupt handler will be invoked. If the System.exit()
       and its shutdown handlers are slow it might be
       very well that a commit happens.

So this is something I called fucked up. If I have time
I will try to file a bug, if there isn't yet one. Filing
a bug should be easy since "GetLastError returns
ERROR_OPERATION_ABORTED" is well documented by MS.

Best Regards

P.S.: I did some measurements. It appears that usually
the readLine() returns before that the INT handler gets
invoiked. The delay is about ~1ms. One can easily
measure it with the new System.nanoTime().

P.S.S.: Therefore I adopetd the workaround of Gabriel
Genellina with a timeout of around 10ms. But this
design is also flawed, it might provoke an unrecognized
EOF. But it is better than nothing...