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Re: Bug in TRE regular expression library
- Subject: Re: Bug in TRE regular expression library
- From: Ralf Junker <ralfjunker%gmx.de@localhost>
- Date: Tue, 20 Jul 2010 22:26:23 +0200
On 20.07.2010 21:58, der Mouse wrote:
>> scanf ("*%s");
> While I can't see it as being your problem,
It surely is not my problem nor the point I wanted to draw attention
to. The focus is solely on the TRE regex functions.
Still, thanks for pointing this out. I never put any thought into this
scanf arguments, simply because they serve a single purpose: Stop the
application so I can read its output and press any key to quit quickly.
Works fine for me here.
I am sorry to say that I am not much concerned about any problems this
key press might cause elsewehere, as this is not a working application
but some simple code to demonstrate a problem somewhere else, possibly
in production code.
Buz if you'd like to suggest a proper way to achieve this objective, I'd
be eager to learn ...
> this looks..questionable, at the very least. If the input line at
> this point begins with a *, scanf will, at best, misuse stack trash
> as if it were a pointer and segfault immediately; more
> pessimistically, misuse stack trash as if it were a pointer and
> scribble on some random data structure somewhere, leading to cryptic
> misbehaviour at some difficult-to-predict later point.
> If the input doesn't begin with a *, I think our implementation will
> not misbehave, but I also think this is an accident of the
> implementation and should not be counted on - I don't think C and/or
> stdio promise that omitting arguments like this is acceptable even
> if they're not stored through. (For example, scanf might fetch the
> pointer, even if it doesn't store through it, and if the machine has
> trap representations for pointers it may crash when doing so.)
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