Merge branch 'maint'

isl_map.c

@@ -2147,19 +2147,22 @@ static __isl_give isl_basic_map *isl_basic_map_swap_vars(
  * Since the basic map has conflicting constraints,
  * it must have at least one constraint, except perhaps
  * if it was already explicitly marked as being empty.
- * Do nothing in the latter case.
+ * Do nothing in the latter case, i.e., if it has been marked empty and
+ * has no constraints.
  */
 __isl_give isl_basic_map *isl_basic_map_set_to_empty(
 	__isl_take isl_basic_map *bmap)
 {
 	int i = 0;
 	isl_bool empty;
+	isl_size n;
 	isl_size total;
 
+	n = isl_basic_map_n_constraint(bmap);
 	empty = isl_basic_map_plain_is_empty(bmap);
-	if (empty < 0)
+	if (n < 0 || empty < 0)
 		return isl_basic_map_free(bmap);
-	if (empty)
+	if (n == 0 && empty)
 		return bmap;
 	total = isl_basic_map_dim(bmap, isl_dim_all);
 	if (total < 0)

isl_test.c

@@ -8693,6 +8693,34 @@ int test_sample(isl_ctx *ctx)
 	return 0;
 }
 
+/* Perform a projection on a basic set that is known to be empty
+ * but that has not been assigned a canonical representation.
+ * Earlier versions of isl would run into a stack overflow
+ * on this example.
+ */
+static int test_empty_projection(isl_ctx *ctx)
+{
+	const char *str;
+	isl_bool empty;
+	isl_basic_set *bset;
+
+	str = "{ [a, b, c, d, e, f, g, h] : 5f = 1 + 4a - b + 5c - d - 2e and "
+		"3h = 2 + b + c and 14c >= 9 - 3a + 25b and "
+		"4c <= 50 - 3a + 23b and 6b <= -39 + a and "
+		"9g >= -6 + 3a + b + c and e < a + b - 2d and "
+		"7d >= -5 + 2a + 2b and 5g >= -14 + a - 4b + d + 2e and "
+		"9g <= -28 - 5b - 2c + 3d + 6e }";
+	bset = isl_basic_set_read_from_str(ctx, str);
+	empty = isl_basic_set_is_empty(bset);
+	bset = isl_basic_set_params(bset);
+	isl_basic_set_free(bset);
+
+	if (empty < 0)
+		return -1;
+
+	return 0;
+}
+
 int test_fixed_power(isl_ctx *ctx)
 {
 	const char *str;
@@ -10825,6 +10853,7 @@ struct {
 	{ "slice", &test_slice },
 	{ "fixed power", &test_fixed_power },
 	{ "sample", &test_sample },
+	{ "empty projection", &test_empty_projection },
 	{ "output", &test_output },
 	{ "vertices", &test_vertices },
 	{ "chambers", &test_chambers },