Re: [Gcl-devel] strings copied across heap/local data boundaries

[Camm Maguire]

Greetings!

"Mike Thomas" <address@hidden> writes:

> Hi Camm.
> 
> | Greetings!  Mike, this sounds quite interesting and promising.
> |
> | The BEGIN/END NO_INTERRUPT macros only govern signal handling.  I'm
> | trying at the moment to reproduce the signal capture in the maxima
> | build that you must be seeing.  Do you have strace?  If so, can you
> | post the results of running the maxima build under strace -f?
> | Alternately,  can you break in main_signal_handler and/or before
> | interrupt and provide a gdb backtrace?  What we may be seeing is that
> | the Windows OS is sending signals to the running process that are
> | simply not being seen on other systems.
> 
> I should have known better as Windows doesn't do signalling as such -
> they're faked up in the C runtime for the sake of compatibility which makes
> the whole idea a bit doubtful.  Never-the-less it could have been a cause.
> Further NO_INTERRUPT bracketing led to a regression rather than improvement
> so although it may be that garbage collection interference is to blame I was
> unable to catch a break in main_signal_handler.
> 
> Can anyone think of another way for GC to occur while copying strings
> around?
> 

Your problem is symptomatic of some mishandling of gc in the static
area or C stack.  

I note the following in main.c:

#ifdef _WIN32
          {
            unsigned int dummy;
            
            _stackbottom = (unsigned int ) &dummy;
            _stacktop    = _stackbottom - 0x10000; // ???

          }
#endif

Is it possible you are underestimating the C stack range, especially
when the ASCI/PCL multi function/C stack consuming error reporting
tree is in effect?  

Also, please give this a whirl:

Index: gbc.c
===================================================================
RCS file: /cvsroot/gcl/gcl/o/gbc.c,v
retrieving revision 1.13.4.2.2.10
diff -u -r1.13.4.2.2.10 gbc.c
--- gbc.c       7 May 2004 21:43:15 -0000       1.13.4.2.2.10
+++ gbc.c       18 May 2004 20:22:01 -0000
@@ -425,7 +426,7 @@
          mark_contblock(cp, j);
       } else if (x->a.a_displaced == Cnil) {
 #ifdef HAVE_ALLOCA
-       if (cp <= core_end)  /* only if body of array not on C stack */
+       if (!NULL_OR_ON_C_STACK(cp))  /* only if body of array not on C stack */
 #endif                   
          x->a.a_self = (object *)copy_relblock(cp, j);}
       else if (x->a.a_displaced->c.c_car == Cnil) {
Index: sgbc.c
===================================================================
RCS file: /cvsroot/gcl/gcl/o/sgbc.c,v
retrieving revision 1.9.4.1.2.11
diff -u -r1.9.4.1.2.11 sgbc.c
--- sgbc.c      7 May 2004 21:43:15 -0000       1.9.4.1.2.11
+++ sgbc.c      18 May 2004 20:22:01 -0000
@@ -313,7 +313,7 @@
        ;
       else if (x->a.a_displaced == Cnil) {
 #ifdef HAVE_ALLOCA
-       if (cp <= core_end)  /* only if body of array not on C stack */
+       if (!NULL_OR_ON_C_STACK(cp))  /* only if body of array not on C stack */
 #endif                   
          x->a.a_self = (object *)copy_relblock(cp, j);
       }


Take care,

> Also improved bcopy() to allow for overlaps but alas no help either.  I'm
> feeling defeated by this at the moment and out of ideas.
> 
> Cheers
> 
> Mike Thomas.
> 
> 
> 
> 
> _______________________________________________
> Gcl-devel mailing list
> address@hidden
> http://mail.gnu.org/mailman/listinfo/gcl-devel
> 
> 
> 

-- 
Camm Maguire                                            address@hidden
==========================================================================
"The earth is but one country, and mankind its citizens."  --  Baha'u'llah