[APPLIED] Memory management bugs

[Steve Fink]

I'll paste a diff -ub below to show the changes without the
reindentation noise.

I am about to commit a patch that:

 - Fixes a bit test bug, changing to
     bits == (bitA | bitB)
   from
     bits == (bitA & bitB))

 - Count of elements in an array of PMCs was wrong. It was looping
   over PMC*'s 0..Buffer->buflen-1, but buflen is a byte size, not
   an element count.

 - Also reformatted some
     else {
         if (...) {
   to be
     else if (...) {
   because it confused me and caused needless line wrapping. But
   mostly I just like it better this way, dammit!

I suspect we need better ways of testing DOD than just doing lots of
collections. There are two types of errors: (1) not collecting dead
objects, and (2) collecting live objects.

For (1), maybe we should add an opcode: get_number_of_live_objects?
Then you could write a test case that records the number of live
objects, does stuff, forces a sweep and collect, and checks that the
saved number + #expected live objects is equal to the currently live
number?

For (2), a compile option that scribbles 010101010101... all over
collected objects? It's not perfect, but it would make it quite a bit
less likely for mistakes to slip by.

diff -u -b -r1.47 resources.c
--- resources.c 25 Apr 2002 21:35:14 -0000      1.47
+++ resources.c 27 Apr 2002 19:11:48 -0000
@@ -360,7 +360,7 @@
   }
 }
 
-static PMC *
+PMC *
 mark_used(PMC *used_pmc, PMC *current_end_of_list) {
 
 
@@ -452,21 +452,19 @@
             if (bits == PMC_is_PMC_ptr_FLAG) {
                 last = mark_used(current->data, last);
             }
-            else {
-                if (bits == PMC_is_buffer_ptr_FLAG) {
+            else if (bits == PMC_is_buffer_ptr_FLAG) {
                     if (current->data) {
                         buffer_lives(current->data);
                     }
                 }
-                else {
-                    if (bits == (PMC_is_buffer_ptr_FLAG &
-                        PMC_is_PMC_ptr_FLAG)) {
+            else if (bits == (PMC_is_buffer_ptr_FLAG | PMC_is_PMC_ptr_FLAG))
+            {
                         /* buffer of PMCs */
                         Buffer *trace_buf = current->data;
                         PMC **cur_pmc = trace_buf->bufstart;
                         /* Mark the damn buffer as used! */
                         trace_buf->flags |= BUFFER_live_FLAG;
-                        for (i = 0; i < trace_buf->buflen; i++) {
+                for (i = 0; i < trace_buf->buflen / sizeof(*cur_pmc); i++) {
                             if (cur_pmc[i]) {
                                 last = mark_used(cur_pmc[i], last);
                             }
@@ -474,12 +472,10 @@
                     }
                     else {
                         /* All that's left is the custom */
-                        last = current->vtable->mark(interpreter,
-                                                     current, last);
-                    }
-                }
+                last = current->vtable->mark(interpreter, current, last);
             }
         }
+
         prev = current;
     }
 }