oops, nasty off-by-one in set_copy

py/objset.c

@@ -27,6 +27,10 @@ static mp_obj_t set_it_iternext(mp_obj_t self_in);
 
 void set_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
     mp_obj_set_t *self = self_in;
+    if (self->set.used == 0) {
+        print(env, "set()");
+        return;
+    }
     bool first = true;
     print(env, "{");
     for (int i = 0; i < self->set.alloc; i++) {
@@ -122,7 +126,7 @@ static mp_obj_t set_copy(mp_obj_t self_in) {
 
     mp_obj_set_t *other = m_new_obj(mp_obj_set_t);
     other->base.type = &set_type;
-    mp_set_init(&other->set, self->set.alloc);
+    mp_set_init(&other->set, self->set.alloc - 1);
     other->set.used = self->set.used;
     memcpy(other->set.table, self->set.table, self->set.alloc * sizeof(mp_obj_t));
 

tests/basics/tests/set_binop.py

@@ -1,29 +1,30 @@
 def r(s):
     l = list(s)
     l.sort()
-    print(l)
-s = {1, 2}
-t = {2, 3}
-r(s | t)
-r(s ^ t)
-r(s & t)
-r(s - t)
-u = s.copy()
-u |= t
-r(u)
-u = s.copy()
-u ^= t
-r(u)
-u = s.copy()
-u &= t
-r(u)
-u = s.copy()
-u -= t
-r(u)
+    return l
+sets = [set(), {1}, {1, 2}, {1, 2, 3}, {2, 3}, {2, 3, 5}, {5}, {7}]
+for s in sets:
+    for t in sets:
+        print(s, '|', t, '=', r(s | t))
+        print(s, '^', t, '=', r(s ^ t))
+        print(s, '&', t, '=', r(s & t))
+        print(s, '-', t, '=', r(s - t))
+        u = s.copy()
+        u |= t
+        print(s, "|=", t, '-->', r(u))
+        u = s.copy()
+        u ^= t
+        print(s, "^=", t, '-->', r(u))
+        u = s.copy()
+        u &= t
+        print(s, "&=", t, "-->", r(u))
+        u = s.copy()
+        u -= t
+        print(s, "-=", t, "-->", r(u))
 
-print(s == t)
-print(s != t)
-print(s > t)
-print(s >= t)
-print(s < t)
-print(s <= t)
+        print(s, '==', t, '=', s == t)
+        print(s, '!=', t, '=', s != t)
+        print(s, '>', t, '=', s > t)
+        print(s, '>=', t, '=', s >= t)
+        print(s, '<', t, '=', s < t)
+        print(s, '<=', t, '=', s <= t)