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Date:	Thu, 16 Mar 2006 15:07:29 -0500
From:	Christopher Faylor <cgf-no-personal-reply-please AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Bug in dlopen() (or following) code in Cygwin1.dll v 1.5.19-4
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On Thu, Mar 16, 2006 at 07:41:18PM +0000, Eric Blake wrote:
>One more thing to be aware of - the reason cygwin uses this (IMHO very
>slick) feature of C++ is that it is more efficient to assume that code
>will not fault, and blindly deference pointers with the minimal
>overhead of setting up the setjmp buffer with a pre-installed exception
>handler already prepared for this usage, than it is to use a syscall to
>Window's routines to validate every pointer before dereferencing it.
>On the exceptional case that the code actually did get passed a bad
>pointer, the overhead of the exception handling and longjmp are slower,
>but that is okay since it is the exception.
>
>So maybe it looks weird.  C++ is like that!

This isn't really c++ working here.  It is basically longjmp working in
concert with cygwin's own exception detection mechanism that is used
when a program gets a SIGSEGV, SIGILL, etc.

cgf

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