Re: signals hanling in octave

[Paul Kienzle]

On Oct 19, 2006, at 4:21 PM, Miroslaw Dach wrote:

> Dear All,
>
>   I am using mex program under octave. The only missing function in 
> octave 2.9.9 implementation (which I need to use) is mexAtExit.
> This function registers the handler function which is call before 
> exiting from Matlab. As the replacement of that function on octave I 
> have tried to use atexit but my function is not call as the first one 
> before closing the octave and octave simply stalls. John has  
> suggested to me to add the pointer in the octave_mex_function class 
> but i am not so familiar with octave code. I was just playing with the 
> standard c signal function to register my handler but I do not know 
> which signal is sent when octave quits.
>
> I would appreciate very much is somebody could help me on that.

The functions you are interested in are in the src directory.

    ov-fcn.h    -  base octave function class
    ov-mex-fcn.{cc,h}  - mex function class
    mex.h, mex.cc   - mex function definitions

One thing you could do is hook into the destructor in ov-mex-fcn.cc. 
Just before removing the function, you can call the 'exit_fcn_ptr' 
handle if it is not 0.  This handle would be stored in the 
octave_mex_function class along with mex_fcn_ptr.  Don't forget to 
initialize it to 0.  Add an at_exit(fcn) method to octave_mex_function 
which sets exit_fcn_ptr.

In class mex defined in mex.cc you will need to define an at_exit(fcn) 
method which sets the exit_fcn_handle of the octave_mex_function 
object.  mexAtExit(fcn) is then a call to mex_context->at_exit(fcn).

Writing mex::at_exit(fcn) will be a bit tricky.

The clean way would be to pass a pointer to the octave_function handle 
'this' through C_mex or Fortran_mex.  Store this handle in class mex 
when it is created.  It can then be used directly by function_name and 
at_exit to access octave_mex_function.

The hackish way is to use the same trick I used when mex was not part 
of Octave, and grab the handle to the currently executing function from 
the octave_call_stack.

I've implemented the hackish way in the attached patch.  I haven't 
tried compiling it or running it so you will have some work ahead of 
you, but this should get you most of the way there.

- Paul

mexAtExit.patch
Description: Binary data