[tarantool-patches] [PATCH v1 1/1] sql: Fix DEFAULTs AST memory leak on alter

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

The space_def_destroy_fields routine is used in make_scoped_guard
on alter:space_def_new_from_tuple always pass extern_alloc=true
for sql_expr_delete routine. It shouldn't as the first-time
allocated AST (field_def_decode) is not external-allocated.
Introduced a new flag 'extern_alloc' for space_def_destroy_fields
routine.

Closes #3908

http://github.com/tarantool/tarantool/tree/kshch/gh-3908-fix-ast-alter-memleak
https://github.com/tarantool/tarantool/issues/3908

---
 src/box/alter.cc    | 4 ++--
 src/box/space_def.c | 7 ++++---
 src/box/space_def.h | 4 +++-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/box/alter.cc b/src/box/alter.cc
index 03ba68adc..5ec57590e 100644
--- a/src/box/alter.cc
+++ b/src/box/alter.cc
@@ -452,7 +452,7 @@ space_format_decode(const char *data, uint32_t *out_count,
 	 */
 	memset(region_defs, 0, size);
 	auto fields_guard = make_scoped_guard([=] {
-		space_def_destroy_fields(region_defs, count);
+		space_def_destroy_fields(region_defs, count, false);
 	});
 	for (uint32_t i = 0; i < count; ++i) {
 		field_def_decode(&region_defs[i], &data, space_name, name_len,
@@ -515,7 +515,7 @@ space_def_new_from_tuple(struct tuple *tuple, uint32_t errcode,
 	fields = space_format_decode(format, &field_count, name,
 				     name_len, errcode, region);
 	auto fields_guard = make_scoped_guard([=] {
-		space_def_destroy_fields(fields, field_count);
+		space_def_destroy_fields(fields, field_count, false);
 	});
 	if (exact_field_count != 0 &&
 	    exact_field_count < field_count) {
diff --git a/src/box/space_def.c b/src/box/space_def.c
index 69b92c5c1..3516bdd8d 100644
--- a/src/box/space_def.c
+++ b/src/box/space_def.c
@@ -259,12 +259,13 @@ space_def_new(uint32_t id, uint32_t uid, uint32_t exact_field_count,
 
 /** Free a default value's syntax trees of @a defs. */
 void
-space_def_destroy_fields(struct field_def *fields, uint32_t field_count)
+space_def_destroy_fields(struct field_def *fields, uint32_t field_count,
+			 bool extern_alloc)
 {
 	for (uint32_t i = 0; i < field_count; ++i) {
 		if (fields[i].default_value_expr != NULL) {
 			sql_expr_delete(sql_get(), fields[i].default_value_expr,
-					true);
+					extern_alloc);
 		}
 	}
 }
@@ -274,7 +275,7 @@ space_def_delete(struct space_def *def)
 {
 	space_opts_destroy(&def->opts);
 	tuple_dictionary_unref(def->dict);
-	space_def_destroy_fields(def->fields, def->field_count);
+	space_def_destroy_fields(def->fields, def->field_count, true);
 	TRASH(def);
 	free(def);
 }
diff --git a/src/box/space_def.h b/src/box/space_def.h
index 0d1e90233..e99581dab 100644
--- a/src/box/space_def.h
+++ b/src/box/space_def.h
@@ -122,9 +122,11 @@ struct space_def {
  * Free a default value syntax trees of @a defs.
  * @param fields Fields array to destroy.
  * @param field_count Length of @a fields.
+ * @param extern_alloc Fields expression AST allocated externally.
  */
 void
-space_def_destroy_fields(struct field_def *fields, uint32_t field_count);
+space_def_destroy_fields(struct field_def *fields, uint32_t field_count,
+			 bool extern_alloc);
 
 /**
  * Delete the space_def object.
-- 
2.19.2