1. Callback error
Hi,
As I'd mentioned earlier, I'm working on a DLL for use with Euphoria. I
figured out how to get the callback, and how to call my euphoria function.
However, I get an error when my program returns to the DLL. I have MS
Visual C++ 6, and the error that pops up is:
-- Start error report
Program: C:\EUPHORIA\BIN\EXW.EXE
Module:
File: i386\chkesp.c
Line 42
The value of ESP was not properly saved across a function call. This is
usually the result of calling a function declared with one calling
convention with a function pointer declared with a different calling
convention.
-- End error report
I've declared my function pointer as:
int (*EuCallBack)(int, int)
It passes values to my euphoria routine just fine, but crashes when it comes
back. My function returns 1. (I've also tried long (*EuCallBack)(int,
int), and I got the same error.) Do I need to do something special to
return to the DLL? Maybe use __stdcl* instead of the default __cdecl*? I
have no idea what i386\chkesp.c or ESP might be.
Hopefully this makes sense to someone out there (Rob?)...
Matthew W Lewis
2. Re: Callback error
ESP - Extra Sensory Perception. The computer is trying to guess
what you wanted to do but failed. o<8^) :)
Okay, ESP - The Extended Stack Pointer. - Stack Pointer for
a program running it protected memory. ESP is a system Register.
Similar to EAX, EBX, ECX, EDX, EBP. These are low level
assembly/machine code values.
This means that your Stack Pointer was corrupted.
You either failed to return when you should have or return the
values to their original state before returning. An other
possibilities can be covered by our resident ASM geeks such as
Pete Eberlein.
Lucius L. Hilley III
lhilley at cdc.net lucius at ComputerCafeUSA.com
+----------+--------------+--------------+----------+
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| Horse +--------------+--------------+ Cafe' |
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----- Original Message -----
From: Matthew Lewis <MatthewL at KAPCOUSA.COM>
To: <EUPHORIA at LISTSERV.MUOHIO.EDU>
Sent: Tuesday, November 02, 1999 11:01 AM
Subject: Callback error
> ---------------------- Information from the mail
header -----------------------
> Sender: Euphoria Programming for MS-DOS
<EUPHORIA at LISTSERV.MUOHIO.EDU>
> Poster: Matthew Lewis <MatthewL at KAPCOUSA.COM>
> Subject: Callback error
> --------------------------------------------------------------------------
-----
>
> Hi,
>
> As I'd mentioned earlier, I'm working on a DLL for use with Euphoria. I
> figured out how to get the callback, and how to call my euphoria function.
> However, I get an error when my program returns to the DLL. I have MS
> Visual C++ 6, and the error that pops up is:
>
> -- Start error report
> Program: C:\EUPHORIA\BIN\EXW.EXE
> Module:
> File: i386\chkesp.c
> Line 42
> The value of ESP was not properly saved across a function call. This is
> usually the result of calling a function declared with one calling
> convention with a function pointer declared with a different calling
> convention.
> -- End error report
>
> I've declared my function pointer as:
>
> int (*EuCallBack)(int, int)
>
> It passes values to my euphoria routine just fine, but crashes when it
comes
> back. My function returns 1. (I've also tried long (*EuCallBack)(int,
> int), and I got the same error.) Do I need to do something special to
> return to the DLL? Maybe use __stdcl* instead of the default __cdecl*? I
> have no idea what i386\chkesp.c or ESP might be.
>
> Hopefully this makes sense to someone out there (Rob?)...
>
> Matthew W Lewis
>
3. Re: Callback error
Switching to a local stack inside your dll might help .
Are you aware that vel uses a DLL maybe you should find out
how they handle that stack.
Bernie
4. Re: Callback error
- Posted by Robert Craig <rds at ATTCANADA.NET>
Nov 02, 1999
-
Last edited Nov 03, 1999
Matthew Lewis writes:
> int (*EuCallBack)(int, int)
> It passes values to my euphoria routine just fine, but
> crashes when it comes back. My function returns 1.
> (I've also tried long (*EuCallBack)(int, int), and I got
> the same error.) Do I need to do something special
> to return to the DLL? Maybe use __stdcl* instead
> of the default __cdecl*?
Try using __stdcall or __stdcl, whatever your compiler
defines for "standard call". It's the calling convention that's
used when a WIN32 API routine is called. The default
calling convention is __cdecl. There's a difference in the
way the call stack is cleaned up after a call. That's probably
why you had a problem. __cdecl allows for a variable number
of arguments to be passed, but the caller is responsible
for cleaning up the stack. With __stdcall, the subroutine
cleans up the stack since it "knows" how many arguments
must have been passed.
Regards,
Rob Craig
Rapid Deployment Software
http://www.RapidEuphoria.com
5. Re: Callback error
Thanks for all the suggestions. Unfortunately, none of them seemed to work
(at least, I couldn't make it happen.) Fortunately, I sidestepped the issue
by passing a pointer and letting the C routines store the data I needed
passed there. This seems to work fine.
I'd be interested to know if anyone else (esp Gary Dumer with VEL, even
though its not written in C) has had a similar problem?
BTW, the project I'm working on is using CLIPS, which is a C based expert
system development language, created by NASA. I recall Ralf talking about
interest in Lisp or Prolog or something with regard to creating an inference
engine in Euphria. That's exactly what CLIPS is about. There are several
sites on the web from which to download versions of CLIPS, including the
source (it's all PD). The CLIPS homepage is at:
http://www.ghgcorp.com/clips/CLIPS.html
if anyone's interested...
Matthew W Lewis
