Re: [OctDev] [PATCH] CVS-octave-forge and GCC3.2

[Paul K. <pki...@ja...>]

On Mon, Nov 25, 2002 at 08:35:11PM +0000, Nix wrote:
> On Sun, 24 Nov 2002, Paul Kienzle said:
> > The reason that won't work is because you need to something to catch it.
> 
> But the catcher is in octave/toplev.cc; it throws right through our code
> and out the other side.
> 
> (I'm sort of assuming that our destructors do all the necessary cleanup;
> if not, we'll need the occasional catch-and-rethrow ourselves.)
> 
> Of course this code only handles errors, not interrupts. For that, see
> below :)
> 
> > That requires putting trapping code around each call to superLU to set
> > the jump return address and reset it when done.  Plus any loops outside
> > of superLU need to have periodic checks if an interrupt has been triggered.
> 
> ... oh, damn and blast, SuperLU is C. I didn't notice and thought it was
> C++.

Maybe all is not lost.  I forgot that we are recompiling superlu ourselves.
When I tested this a couple of years ago, I found that I could do something
like:

main.cc:

#include <iostream>

extern "C" { void throw_back(void); }
extern "C" { void C_stuff(void); }

class myexception {};
void throw_back(void) { throw myexception(); }

int main(int argc, char *argv[])
{
   try {
	C_stuff();
	std::cout << "not caught" << std::endl;
   } catch (myexception) {
        std::cout << "caught" << std::endl;
   }
   return 0;
}

lib.c:

void C_stuff(void)
{
  void throw_back(void);

  throw_back();
}

Makefile:

all: main.o lib.o
	g++ main.o lib.o -o throw_back

main.o: main.cc
	g++ -c main.cc -o main.o

lib.o: lib.c
	gcc -c -fexceptions lib.c -o lib.o


This seems to still work.  I don't know what to throw though.

	octave_throw_interrupt_exception() ?
	octave_throw_bad_alloc() ?

If this works, I can push out a new octave-forge very soon,
but Ctrl-C will not be responsive within superLU.  

For Ctrl-C we need to put OCTAVE_QUIT in all the inner loops of *.{cc,h}
and wrap calls to superLU with BEGIN/END_INTERRUPT_WITH_EXCEPTIONS.
At least I think that's what we are supposed to do.

It's not clear how we can clean up a superLU malloc which was interrupted
during initialization.  I believe that's why garbage collection was
invented.

> 
> OK, C that counts as foreign code, so calls into SuperLU will require
> BEGIN_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE /
> END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE wrapped around them. That
> should let the code flow when interrupted by SIGINT within SuperLU go
> 
> SIGINT -> signal handler in octave's src/sighandlers.cc ->
> octave_jump_to_enclosing_context() -> longjmp() to the
> END_INTERRUPT_IMMEDIATELY_IN_FOREIGN_CODE -> Octave's toplev.cc.
> 
> > The macros to do this are in quit.h, but I don't know the exact magic.
> 
> I think I've decrypted it.
> 
> > Let me know if you are going to persue this, because it is top of my list
> 
> It's top of mine too. Patch in an hour or so (this box is running rather
> slowly right now, alas, and it would be inurbane for me to antinice
> everyone else into oblivion).
> 
> > (right behind family and work that is, which in this season puts it 
> > much too far back ;-)
> 
> :)
> 
> -- 
> `I keep hearing about SF writers dying, but I never hear about SF
>  writers being born.  So I guess eventually there'll be none left.'
>                                     -- Keith F. Lynch
>