Branch: https://github.com/tarantool/luajit/tree/ligurio/gh-1279-recording-getmetatable

LJ issue: https://github.com/LuaJIT/LuaJIT/issues/1279

From: Sergey Bronnikov <sergeyb@tarantool.org>

The patch fixes a problem with recording `getmetatable()`
for I/O object: recording of `getmetatable` call with a file
descriptors represented by userdata object `UDTYPE_IO_FILE`
(like `io.stdout`) leads to violation of assertion in
`rec_check_slots`.

Note, the problem was fixed upstream in different manner, see
commit 5141cbc20c43
("Fix compiliation of getmetatable() for UDTYPE_IO_FILE.").
---
 src/lj_record.c                               |  2 +-
 ...-incorrect-recording-getmetatable.test.lua | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 test/tarantool-tests/lj-1279-incorrect-recording-getmetatable.test.lua

diff --git a/src/lj_record.c b/src/lj_record.c
index cc97bdf9..7181b72a 100644
--- a/src/lj_record.c
+++ b/src/lj_record.c
@@ -990,7 +990,7 @@ int lj_record_mm_lookup(jit_State *J, RecordIndex *ix, MMS mm)
     int udtype = udataV(&ix->tabv)->udtype;
     mt = tabref(udataV(&ix->tabv)->metatable);
     /* The metatables of special userdata objects are treated as immutable. */
-    if (udtype != UDTYPE_USERDATA) {
+    if (udtype > UDTYPE_IO_FILE) {
       cTValue *mo;
       if (LJ_HASFFI && udtype == UDTYPE_FFI_CLIB) {
 	/* Specialize to the C library namespace object. */
diff --git a/test/tarantool-tests/lj-1279-incorrect-recording-getmetatable.test.lua b/test/tarantool-tests/lj-1279-incorrect-recording-getmetatable.test.lua
new file mode 100644
index 00000000..8bf22ca7
--- /dev/null
+++ b/test/tarantool-tests/lj-1279-incorrect-recording-getmetatable.test.lua
@@ -0,0 +1,21 @@
+local tap = require('tap')
+
+local test = tap.test('lj-1279-incorrect-recording-getmetatable')
+test:plan(1)
+
+-- A test file to demonstrate an incorrect recording of
+-- getmetatable() for I/O handlers.
+-- https://github.com/LuaJIT/LuaJIT/issues/1279
+
+jit.opt.start("hotloop=1")
+
+local obj = io.stdout
+local getmetatable = getmetatable
+
+for _ = 1, 4 do
+  _ = getmetatable(obj)
+end
+
+test:ok(true, 'getmetatable() recording is correct')
+
+test:done(true)