feature/noverlay a154259bfa 3/5: Simplify itree_null initialization

[Stefan Monnier]

branch: feature/noverlay
commit a154259bfacf7f1406794a952e80a8197b9a83fb
Author: Matt Armstrong <matt@rfc20.org>
Commit: Matt Armstrong <matt@rfc20.org>

    Simplify itree_null initialization
    
    * src/itree.c (null_is_sane): call eassert directly, check
    REAR_ADVANCE, FRONT_ADVANCE.  Add FIXME that PARENT is still
    read/write.
    (itree_null): initialize statically
    (itree_init): remove initialization code, call eassert(null_is_sane())
    (check_tree_common): call eassert (null_is_sane())
---
 src/itree.c | 52 ++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 16 deletions(-)

diff --git a/src/itree.c b/src/itree.c
index 7ac400398b..d9f9ec8cd6 100644
--- a/src/itree.c
+++ b/src/itree.c
@@ -145,19 +145,42 @@ static struct interval_generator* 
interval_generator_create (struct interval_tre
 static void interval_tree_insert (struct interval_tree *, struct interval_node 
*);
 
 /* The sentinel node, the null node.  */
-struct interval_node itree_null;
+struct interval_node itree_null = {
+  .parent = &itree_null,
+  .left = &itree_null,
+  .right = &itree_null,
+  .begin = PTRDIFF_MIN,
+  .end = PTRDIFF_MIN,
+  .limit = PTRDIFF_MIN, /* => max(x, null.limit) = x */
+  .offset = 0,
+  .otick = 0,
+  .red = false,
+  .rear_advance = false,
+  .front_advance = false,
+};
 
 static bool
 null_is_sane (void)
 {
-  /* The sentinel node has most of its fields read-only, except for `parent`,
-     `left`, `right` which are write only.  */
-  return itree_null.red == false
-         && itree_null.otick == 0
-         && itree_null.offset == 0
-         && itree_null.begin == PTRDIFF_MIN
-         && itree_null.end == PTRDIFF_MIN
-         && itree_null.limit == PTRDIFF_MIN;
+  /* The sentinel node has most of its fields read-only.
+
+     FIXME: PARENT is still read/write.  It is written to
+     ininterval_tree_transplant, and later read.  --matt
+  */
+  /* eassert (itree_null.parent == &itree_null); */
+  eassert (itree_null.left == &itree_null);
+  eassert (itree_null.right == &itree_null);
+  eassert (itree_null.begin == PTRDIFF_MIN);
+  eassert (itree_null.end == PTRDIFF_MIN);
+  eassert (itree_null.limit == PTRDIFF_MIN);
+  eassert (itree_null.offset == 0);
+  eassert (itree_null.otick == 0);
+  eassert (itree_null.red == false);
+  eassert (itree_null.rear_advance == false);
+  eassert (itree_null.front_advance == false);
+
+  /* if we get this far things must be good */
+  return true;
 }
 
 /* 
+------------------------------------------------------------------------------------+
 */
@@ -195,13 +218,8 @@ static struct interval_generator *iter;
 static void
 itree_init (void)
 {
-  struct interval_node *null = ITREE_NULL;
-  null->left = null->right = null->parent = null;
-  null->offset = null->otick = 0;
-  null->begin = PTRDIFF_MIN;
-  null->end = PTRDIFF_MIN;
-  null->limit = PTRDIFF_MIN;     /* => max(x, null.limit) = x */
-  null->red = false;
+  eassert (null_is_sane ());
+
   iter = interval_generator_create (NULL);
 }
 
@@ -327,6 +345,8 @@ static bool
 check_tree_common (struct interval_tree *tree,
                    bool check_red_black_invariants)
 {
+  eassert (null_is_sane ());
+
   eassert (tree != NULL);
   eassert (tree->size >= 0);
   eassert ((tree->size == 0) == (tree->root == ITREE_NULL));