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Topic: Making C++ objects persistent between mex calls, and robust.
Replies: 37   Last Post: Sep 27, 2013 6:54 AM

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Rune Allnor

Posts: 4,455
Registered: 12/7/04
Re: Making C++ objects persistent between mex calls, and robust.
Posted: Jan 23, 2011 2:55 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On Jan 22, 9:55 pm, "newuser asdf" <sabine.schnei...@rolmail.net>
wrote:
> Hello,
>
> I have some problems in understanding, how this way of object address passing works in my concrete example... Perhaps someone can give me a hint, what I'm doing wrong?
>
> My task: I'm trying to create an instance of a C++ object in a mex file, which then should return its memory address, and another mex function (called afterwards) gets this address as a parameter and calls some functions on it.


Don't do that.

You are traversing at least two more layers of software
interference than you would normally care about:

Your C++ function interacts with the OS to translate the
pointer to a physical address in the RAM chips on the
memory rack inside your computer. You usually don't care
about this - the C++ compiler hides all the dirty details
from the programmer.

When you return back to matlab, you enter a world where
Java is a dominant player. As I understand it, the
matlab user interface (where you access the workspaces etc)
are programmed in Java, in which case the Java interpterer
starts messing things up. And the Java interpterer, too,
interacts with the OS. Not necessarily in exactly the same
way that the C++ compiler does, though.

So in order to get back to the physical address where your
C++ object resides, you need to *ensure* that whatever you
do is robust with respect to the interaction of *both* the
Java interpreter *and* the OS.

*Ensuring* that all this works is by no means easy if the
system design is not intended for these kinds of things.
Which matlab isn't.

Find a different way to achieve what you want.

Rune


Date Subject Author
4/1/10
Read Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
6/7/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Anthony Halley
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Walter Roberson
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Anthony Halley
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
1/22/11
Read Re: Making C++ objects persistent between mex calls, and robust.
newuser asdf
1/22/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Bruno Luong
1/23/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Rune Allnor
1/23/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Bruno Luong
1/23/11
Read Re: Making C++ objects persistent between mex calls, and robust.
newuser asdf
1/24/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
2/3/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Pierre
2/3/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
2/3/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Pierre
2/3/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
2/15/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Pierre
7/6/11
Read Re: Making C++ objects persistent between mex calls, and robust.
mathias
7/6/11
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
5/24/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Ajay
5/25/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Pierre
10/2/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
11/7/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Francesco Montorsi
11/8/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
11/9/12
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
1/21/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
1/22/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
1/30/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Gabri Gwala
1/30/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Steven Lord
1/31/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
9/22/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Gabri Gwala
9/22/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Gabri Gwala
9/27/13
Read Re: Making C++ objects persistent between mex calls, and robust.
Oliver Woodford
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Anthony Halley
6/8/10
Read Re: Making C++ objects persistent between mex calls, and robust.
Anthony Halley

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