Fixed a bug that led to core dumps due to a C decrement operation in a

macro invocation in load_pop.  (BAD)

I fixed this by moving the decrement outside
the macro call.

I added a comment to load_pop and load_mark to document the fact that
cPickle separates the unpickling stack into two separate stacks, one
for objects and one for marks.

I also moved some increments out of some macro calls (PyTuple_SET_ITEM
and PyList_SET_ITEM).  This wasn't necessary, but made me feel better.

lib/Components/cPickle/cPickle.c

 /*
- * $Id: cPickle.c,v 1.71 1999/07/11 13:30:34 jim Exp $
+ * $Id: cPickle.c,v 1.72 2000/05/09 18:05:09 jim Exp $
  * 
  * Copyright (c) 1996-1998, Digital Creations, Fredericksburg, VA, USA.  
  * All rights reserved.
@@ -49,7 +49,7 @@
 static char cPickle_module_documentation[] = 
 "C implementation and optimization of the Python pickle module\n"
 "\n"
-"$Id: cPickle.c,v 1.71 1999/07/11 13:30:34 jim Exp $\n"
+"$Id: cPickle.c,v 1.72 2000/05/09 18:05:09 jim Exp $\n"
 ;
 
 #include "Python.h"
@@ -247,8 +247,8 @@ Pdata_popTuple(Pdata *self, int start) {
 
     l=self->length-start;
     UNLESS (r=PyTuple_New(l)) return NULL;
-    for (i=start, j=0 ; j < l; )
-        PyTuple_SET_ITEM(r,j++,self->data[i++]);
+    for (i=start, j=0 ; j < l; i++, j++)
+        PyTuple_SET_ITEM(r, j, self->data[i]);
 
     self->length=start;
     return r;
@@ -261,8 +261,8 @@ Pdata_popList(Pdata *self, int start) {
 
     l=self->length-start;
     UNLESS (r=PyList_New(l)) return NULL;
-    for (i=start, j=0 ; j < l; )
-        PyList_SET_ITEM(r,j++,self->data[i++]);
+    for (i=start, j=0 ; j < l; i++, j++)
+        PyList_SET_ITEM(r, j, self->data[i]);
 
     self->length=start;
     return r;
@@ -2976,11 +2976,19 @@ load_pop(Unpicklerobject *self) {
 
     UNLESS ((len=self->stack->length) > 0) return stackUnderflow();
 				
+    /* Note that we split the (pickle.py) stack into two stacks, 
+       an object stack and a mark stack. We have to be clever and
+       pop the right one. We do this by looking at the top of the
+       mark stack.
+    */
     if ((self->num_marks > 0) && 
         (self->marks[self->num_marks - 1] == len))
         self->num_marks--;
-    else 
-        Py_DECREF(self->stack->data[--(self->stack->length)]);
+    else { 
+        len--;
+        Py_DECREF(self->stack->data[len]);
+	self->stack->length=len;
+    }
 
     return 0;
 }
@@ -3306,6 +3314,11 @@ static int
 load_mark(Unpicklerobject *self) {
     int s;
 				
+    /* Note that we split the (pickle.py) stack into two stacks, an
+       object stack and a mark stack. Here we push a mark onto the
+       mark stack.  
+    */
+
     if ((self->num_marks + 1) >= self->marks_size) {
         s=self->marks_size+20;
         if (s <= self->num_marks) s=self->num_marks + 1;
@@ -4369,7 +4382,7 @@ init_stuff(PyObject *module, PyObject *module_dict) {
 DL_EXPORT(void)
 initcPickle() {
     PyObject *m, *d, *v;
-    char *rev="$Revision: 1.71 $";
+    char *rev="$Revision: 1.72 $";
     PyObject *format_version;
     PyObject *compatible_formats;