From Lua 5.2: __len for tables. Needs -DLUAJIT_ENABLE_LUA52COMPAT.

1 files changed, 11 insertions, 2 deletions

diff --git a/src/lj_meta.c b/src/lj_meta.c
index fcb9df66..278d2d34 100644
--- a/src/lj_meta.c
+++ b/src/lj_meta.c
@@ -309,10 +309,19 @@ TValue * LJ_FASTCALL lj_meta_len(lua_State *L, cTValue *o)
 {
   cTValue *mo = lj_meta_lookup(L, o, MM_len);
   if (tvisnil(mo)) {
-    lj_err_optype(L, o, LJ_ERR_OPLEN);
-    return NULL;  /* unreachable */
+#ifdef LUAJIT_ENABLE_LUA52COMPAT
+    if (tvistab(o))
+      tabref(tabV(o)->metatable)->nomm |= (uint8_t)(1u<<MM_len);
+    else
+#endif
+      lj_err_optype(L, o, LJ_ERR_OPLEN);
+    return NULL;
   }
+#ifdef LUAJIT_ENABLE_LUA52COMPAT
+  return mmcall(L, lj_cont_ra, mo, o, o);
+#else
   return mmcall(L, lj_cont_ra, mo, o, niltv(L));
+#endif
 }
 
 /* Helper for equality comparisons. __eq metamethod. */