[Tarantool-patches] [PATCH 1/5] uuid: introduce and use luaL_pushuuidstr()

[Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

The function safely pushes tt_uuid as a string on a Lua stack.
Safety means that it does not use tt_uuid_str() which stores the
result into the global static buffer and can not be used in Lua
context.

The static buffer is not safe to use in Lua and Lua C because
during a static string push onto a Lua stack the GC might be
started and it can spoil the buffer.

Part of #6259
---
 src/box/lua/net_box.c |  4 +---
 src/lua/utils.c       | 13 +++++++++++++
 src/lua/utils.h       |  3 +++
 3 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/box/lua/net_box.c b/src/box/lua/net_box.c
index 3f43872ca..d1c7bedf6 100644
--- a/src/box/lua/net_box.c
+++ b/src/box/lua/net_box.c
@@ -422,7 +422,6 @@ netbox_decode_greeting(lua_State *L)
 	struct greeting greeting;
 	size_t len;
 	const char *buf = NULL;
-	char uuid_buf[UUID_STR_LEN + 1];
 
 	if (lua_isstring(L, 1))
 		buf = lua_tolstring(L, 1, &len);
@@ -443,8 +442,7 @@ netbox_decode_greeting(lua_State *L)
 	lua_pushlstring(L, greeting.salt, greeting.salt_len);
 	lua_setfield(L, -2, "salt");
 
-	tt_uuid_to_string(&greeting.uuid, uuid_buf);
-	lua_pushstring(L, uuid_buf);
+	luaL_pushuuidstr(L, &greeting.uuid);
 	lua_setfield(L, -2, "uuid");
 
 	return 1;
diff --git a/src/lua/utils.c b/src/lua/utils.c
index 34cec0eed..bcd647827 100644
--- a/src/lua/utils.c
+++ b/src/lua/utils.c
@@ -37,6 +37,7 @@
 #include <trivia/util.h>
 #include <diag.h>
 #include <fiber.h>
+#include "uuid/tt_uuid.h"
 
 int luaL_nil_ref = LUA_REFNIL;
 
@@ -107,6 +108,18 @@ luaL_pushuuid(struct lua_State *L)
 	return luaL_pushcdata(L, CTID_UUID);
 }
 
+void
+luaL_pushuuidstr(struct lua_State *L, const struct tt_uuid *uuid)
+{
+	/*
+	 * Do not use a global buffer. It might be overwritten if GC starts
+	 * working.
+	 */
+	char str[UUID_STR_LEN + 1];
+	tt_uuid_to_string(uuid, str);
+	lua_pushlstring(L, str, UUID_STR_LEN);
+}
+
 int
 luaL_iscdata(struct lua_State *L, int idx)
 {
diff --git a/src/lua/utils.h b/src/lua/utils.h
index 947d9240b..804fc9548 100644
--- a/src/lua/utils.h
+++ b/src/lua/utils.h
@@ -73,6 +73,9 @@ extern uint32_t CTID_UUID;
 struct tt_uuid *
 luaL_pushuuid(struct lua_State *L);
 
+void
+luaL_pushuuidstr(struct lua_State *L, const struct tt_uuid *uuid);
+
 /** \cond public */
 
 /**
-- 
2.24.3 (Apple Git-128)