mmd for bitwise_and causes a segfault with my pmc types

[Mehmet Yavuz Selim Soyturk]

Hello,

I have two pmc classes PjsNumber and PjsBoolean, which define
bitwise_and like this:

   PMC* bitwise_and(PMC* value, PMC* dest) {
       FLOATVAL a, b;
       if (! dest) {
           dest = pmc_new(INTERP, dynpmc_PjsNumber);
       } else if (dest->vtable->base_type != dynpmc_PjsNumber) {
           VTABLE_morph(INTERP, dest, dynpmc_PjsNumber);
       }
       a = DYNSELF.get_number();
       b = VTABLE_get_number(INTERP, value);
       VTABLE_set_number_native(INTERP, dest, (INTVAL)a & (INTVAL)b);
       return dest;
   }

It seems to work in general, but in some cases (especially when I
allocate too much memory) it causes me a segfault
or an error like: Trace/breakpoint trap (core dumped)

An example of such a case:

.HLL 'Pjs', 'pjs_group'
.loadlib 'pjs_group_ops'

.sub _ :main
   use_much_memory()
   test()
.end

.sub test :anon
   .local pmc a, b, c, d, e
   a = new .PjsBoolean
   b = new .PjsNumber
   c = new .PjsNumber
   d = new .PjsNumber
   e = new .PjsNumber

   c = a & b
   trace 1
   e = c & d
.end

.sub use_much_memory
   $P0 = new .ResizablePMCArray
   $I0 = 0
 loop:
   $P1 = new .String
   $P1 = 'hello world'
   $P0[$I0] = $P1
   inc $I0
   if $I0 < 100000 goto loop
   .return ($P0)
.end


~/parrot_svn/parrot/languages/pjs$ parrot mmd.pir
   43 bitwise_and P4, P2, P3           P4=PjsNumber=PMC(0xb62aa00c)
P2=PjsNumber=PMC(0xb62aa034) P3=PjsNumber=PMC(0xb62aa020)
Trace/breakpoint trap (core dumped)

~/parrot_svn/parrot/languages/pjs$ parrot --no-gc mmd.pir
   43 bitwise_and P4, P2, P3           P4=PjsNumber=PMC(0xb60c0fa8)
P2=PjsNumber=PMC(0xb60c0fd0) P3=PjsNumber=PMC(0xb60c0fbc)
Segmentation fault (core dumped)


I am new to debugging, but (if I didn't do anything wrong) I think
that the problem resides in the mmd table of bitwise_and.

in function mmd_dispatch_p_ppp in src/mmd.c, while executing the
second bitwise_and:


   real_function = (mmd_f_p_ppp)get_mmd_dispatcher(interp,
           left, right, func_nr, &is_pmc); // is_pmc is set to 0
here, but I set it to 1 from the debugger

   if (is_pmc) {
       PMC * const sub = (PMC*)real_function; // if I look at the
contents of sub, it is a .String pmc with content "Hello world"


I have the same problem with bitwise_or. I am suspecting that the mmd
table gets somehow overwritten, but I wasn't capable of finding out
if/how it's.

Any ideas? Did I do something wrong implementing my PMC's, or could it
be a general parrot problem? But I couldn't trigger the same problem
with parrot .Integer or .Float types.

--
Mehmet