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From: swishhh on 19 Jan 2007 19:21
Hi!

I have the problem, that my EAX sometimes points on a unreadable area,
because it is unallocated or the program has not the right.

I call a function of a DLL. The returned value in EAX shall point to a
structure. When the function fails, it returns a value, which points on
a unreadable area. Trying to access [EAX] fails. Is there a possibility
to check - without 'SetUnhandledExceptionFilter' - if EAX points on a
readable value? Is there a test flag??

I would not really like to use exception handeling, because it slows
the application down. I CAN NOT use a different DLL.


Thanks,

Sasha Gunthers

From: David Jones on 19 Jan 2007 20:06
swishhh <dungspace(a)gmx.de> wrote...
> I have the problem, that my EAX sometimes points on a unreadable area,
> because it is unallocated or the program has not the right.
>
> I call a function of a DLL. The returned value in EAX shall point to a
> structure. When the function fails, it returns a value, which points on
> a unreadable area. Trying to access [EAX] fails. Is there a possibility
> to check - without 'SetUnhandledExceptionFilter' - if EAX points on a
> readable value? Is there a test flag??
>
> I would not really like to use exception handeling, because it slows
> the application down. I CAN NOT use a different DLL.

I presume that you're talking about the Microsoft Windows platform due
to the references to SetUnhandledExceptionFilter. If so, you'd probably
have better luck asking in a platform-specific group rather than in a
language group -- this is not an assembly language problem, but a
general Windows problem. Put another way, your question is: "How can I
know if a pointer is valid?"

That having been said, you might want to check out VirtualQuery.

http://msdn2.microsoft.com/en-us/library/aa366902.aspx

David
From: santosh on 19 Jan 2007 22:57
swishhh wrote:
> Hi!
>
> I have the problem, that my EAX sometimes points on a unreadable area,
> because it is unallocated or the program has not the right.
>
> I call a function of a DLL. The returned value in EAX shall point to a
> structure. When the function fails, it returns a value, which points on
> a unreadable area. Trying to access [EAX] fails. Is there a possibility
> to check - without 'SetUnhandledExceptionFilter' - if EAX points on a
> readable value? Is there a test flag??
>
> I would not really like to use exception handeling, because it slows
> the application down. I CAN NOT use a different DLL.

Look up the docs on msdn.com. There're functions named isValidPtr() or
something to that effect which check your pointer's value for
deferencability.

From: LocoDelAssembly on 19 Jan 2007 23:06
You can use http://win32assembly.online.fr/Exceptionhandling.html which
not relies on SetUnhandledExceptionFilter or
http://msdn2.microsoft.com/en-us/library/aa366713.aspx (IsBadReadPtr)

swishhh ha escrito:
> Hi!
>
> I have the problem, that my EAX sometimes points on a unreadable area,
> because it is unallocated or the program has not the right.
>
> I call a function of a DLL. The returned value in EAX shall point to a
> structure. When the function fails, it returns a value, which points on
> a unreadable area. Trying to access [EAX] fails. Is there a possibility
> to check - without 'SetUnhandledExceptionFilter' - if EAX points on a
> readable value? Is there a test flag??
>
> I would not really like to use exception handeling, because it slows
> the application down. I CAN NOT use a different DLL.
>
>
> Thanks,
>
> Sasha Gunthers

From: David Jones on 19 Jan 2007 23:47
IsBadReadPtr isn't a good idea.

http://blogs.msdn.com/larryosterman/archive/2004/05/18/134471.aspx
http://blogs.msdn.com/oldnewthing/archive/2006/09/27/773741.aspx

David

LocoDelAssembly <ellocodelassembler(a)gmail.com> wrote...
> You can use http://win32assembly.online.fr/Exceptionhandling.html which
> not relies on SetUnhandledExceptionFilter or
> http://msdn2.microsoft.com/en-us/library/aa366713.aspx (IsBadReadPtr)
>
> swishhh ha escrito:
> > Hi!
> >
> > I have the problem, that my EAX sometimes points on a unreadable area,
> > because it is unallocated or the program has not the right.
> >
> > I call a function of a DLL. The returned value in EAX shall point to a
> > structure. When the function fails, it returns a value, which points on
> > a unreadable area. Trying to access [EAX] fails. Is there a possibility
> > to check - without 'SetUnhandledExceptionFilter' - if EAX points on a
> > readable value? Is there a test flag??
> >
> > I would not really like to use exception handeling, because it slows
> > the application down. I CAN NOT use a different DLL.
> >
> >
> > Thanks,
> >
> > Sasha Gunthers
>
>
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