Stop assuming interval pointers and lisp objects can be distinguished by

inspection.  Beginnings of support for expensive internal consistency checks.

* config.in (ENABLE_CHECKING): Undef.

* lisp.h (struct interval): Replace "parent" field with a union of interval
pointer and Lisp_Object; add new bitfield to use as discriminant.  Change other
flag fields to bitfields.
(CHECK): New macro for consistency checking.  If ENABLE_CHECKING is defined and
the supplied test fails, print a message and abort.
(eassert): New macro.  Use CHECK to provide an assert-like facility.

* intervals.h (NULL_INTERVAL_P): Now applies only to real interval pointers;
abort if the value looks like a lisp object.
(NULL_INTERVAL_P, NULL_PARENT, HAS_PARENT, HAS_OBJECT, SET_PARENT, SET_OBJECT,
INTERVAL_PARENT, GET_INTERVAL_OBJECT, COPY_PARENT): Modify for new interval
parent definition.

* alloc.c (mark_interval_tree, MARK_INTERVAL_TREE, UNMARK_BALANCE_INTERVALS):
Update references that need an addressable lisp object in the interval
structure.
(die): New function.
(suppress_checking): New variable.

* intervals.c (interval_start_pos): Just return 0 if there's no parent object.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/intervals.c b/src/intervals.c
index 2a03abbb762..f925d222db2 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -570,6 +570,8 @@ interval_start_pos (source)
   if (NULL_INTERVAL_P (source))
     return 0;
 
+  if (! INTERVAL_HAS_OBJECT (source))
+    return 0;
   GET_INTERVAL_OBJECT (parent, source);
   if (BUFFERP (parent))
     return BUF_BEG (XBUFFER (parent));