segtree: sort set elements before decomposition

The decomposition phase currently depends on the kernel returning elements
in sorted order. This is a fragile assumption, change the code to sort the
elements itself.

Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/src/segtree.c b/src/segtree.c
index c169f8d16bec72497320b4d387db6c0896281888..1785f640feb45c137abfb14d81b87d33146ec668 100644 (file)
--- a/src/segtree.c
+++ b/src/segtree.c
@@ -516,23 +516,39 @@ static struct expr *expr_value(struct expr *expr)
                return expr;
 }
 
+static int expr_value_cmp(const void *p1, const void *p2)
+{
+       struct expr *e1 = *(void * const *)p1;
+       struct expr *e2 = *(void * const *)p2;
+
+       return mpz_cmp(expr_value(e1)->value, expr_value(e2)->value);
+}
+
 void interval_map_decompose(struct expr *set)
 {
-       struct expr *ranges[set->size * 2];
+       struct expr *elements[set->size], *ranges[set->size * 2];
        struct expr *i, *next, *low = NULL, *end;
-       unsigned int n, size;
+       unsigned int n, m, size;
        mpz_t range, p;
        bool interval;
 
        mpz_init(range);
        mpz_init(p);
 
-       size = set->size;
+       /* Sort elements */
        n = 0;
+       list_for_each_entry_safe(i, next, &set->expressions, list) {
+               compound_expr_remove(set, i);
+               elements[n++] = i;
+       }
+       qsort(elements, n, sizeof(elements[0]), expr_value_cmp);
+       size = n;
 
+       /* Transform points (single values) into half-closed intervals */
+       n = 0;
        interval = false;
-       list_for_each_entry_safe_reverse(i, next, &set->expressions, list) {
-               compound_expr_remove(set, i);
+       for (m = 0; m < size; m++) {
+               i = elements[m];
 
                if (i->flags & EXPR_F_INTERVAL_END)
                        interval = false;
@@ -540,12 +556,12 @@ void interval_map_decompose(struct expr *set)
                        end = expr_clone(expr_value(i));
                        end->flags |= EXPR_F_INTERVAL_END;
                        ranges[n++] = end;
-                       size++;
                } else
                        interval = true;
 
                ranges[n++] = i;
        }
+       size = n;
 
        for (n = 0; n < size; n++) {
                i = ranges[n];