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Date:	Tue, 24 Sep 2002 16:41:30 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: problems with mprotect()
Message-ID:	<20020924164130.Q29920@cygbert.vinschen.de>
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On Mon, Sep 23, 2002 at 07:21:22PM -0700, Anonymous wrote:
> Hi, I'm having segfaults with the following piece of code (working from
> WinXP SP1 using latest Cygwin release):
> 
> char * AllocBoundedArray(int size)
> {
> 	int pgSize = getpagesize();
> 	char *ptr = new char[pgSize * 2 + size];
> 	// before
> 	mprotect(ptr, pgSize, 0);
>         // after
> 	mprotect(ptr + pgSize + size, pgSize, 0);
> 	return ptr + pgSize;
> }

The code expects that a new or malloc returns the memory on a
page boundary.  That's incorrect.  It's virtually certain that
it protects memory to NOACCESS which isn't owned by the above
new().  Whatever this is, it's non-portable.

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.

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