Re: [AD] mzscheme bindings in svn

[Jon Rafkind <workmin@xxxxxxxxxx>]

Peter Wang wrote:
> On 2007-04-28, Jon Rafkind <workmin@xxxxxxxxxx> wrote:
>   
> > Oh wait I forgot. I did change one fundamental thing about Allegro. In 
> > src/x/xsystem.c I had to comment out the signal stuff because mzscheme 
> > uses signals for write-barriers with the garbage collector:
> >
> > static int _xwin_sysdrv_init(void)
> > {
> >    char tmp[256];
> >
> >    _unix_read_os_type();
> >    /*
> >    old_sig_abrt = signal(SIGABRT, _xwin_signal_handler);
> >    old_sig_fpe  = signal(SIGFPE,  _xwin_signal_handler);
> >    old_sig_ill  = signal(SIGILL,  _xwin_signal_handler);
> >    old_sig_segv = signal(SIGSEGV, _xwin_signal_handler);
> >    old_sig_term = signal(SIGTERM, _xwin_signal_handler);
> >    old_sig_int  = signal(SIGINT,  _xwin_signal_handler);
> >
> > #ifdef SIGQUIT
> >    old_sig_quit = signal(SIGQUIT, _xwin_signal_handler);
> > #endif
> > */
> >
> > Maybe we can wrap those with a
> > if ( global_use_signals ){
> >   ...
> > }
> > or something?
> >     
>
> That would be fine (but call it __al_xwin_dont_install_signal_handlers
> or something).  A dirtier solution would be to save the MzScheme signal
> handlers before calling allegro_init(), then restore them immediately
> afterwards.  This would work with current and older versions of Allegro.
>
>   
I think messing with the invariants about the garbage collector is 
tricky business and might lead to very strange results. I'd rather use 
the _al_xwin_install_signal_handlers way.
> OTOH, which signals are MzScheme using?  Surely not SIGABRT, SIGSEGV,
> SIGTERM, SIGQUIT?
>
>   
I think it just uses SIGSEGV and SIGBUS.

GC_old_bus_handler = signal(SIGBUS, GC_write_fault_handler);
GC_old_segv_handler = signal(SIGSEGV, (SIG_PF)GC_write_fault_handler);

Those are the only signals I see it setting with signal().