3 files changed, 6 insertions, 2 deletions

diff --git a/src/lib_base.c b/src/lib_base.c
index 887fea7a..ca268b1d 100644
--- a/src/lib_base.c
+++ b/src/lib_base.c
@@ -435,13 +435,13 @@ LJLIB_CF(gcinfo)
 LJLIB_CF(collectgarbage)
 {
   int opt = lj_lib_checkopt(L, 1, LUA_GCCOLLECT,  /* ORDER LUA_GC* */
-    "\4stop\7restart\7collect\5count\1\377\4step\10setpause\12setstepmul");
+    "\4stop\7restart\7collect\5count\1\377\4step\10setpause\12setstepmul\1\377\11isrunning");
   int32_t data = lj_lib_optint(L, 2, 0);
   if (opt == LUA_GCCOUNT) {
     setnumV(L->top, (lua_Number)G(L)->gc.total/1024.0);
   } else {
     int res = lua_gc(L, opt, data);
-    if (opt == LUA_GCSTEP)
+    if (opt == LUA_GCSTEP || opt == LUA_GCISRUNNING)
       setboolV(L->top, res);
     else
       setintV(L->top, res);
diff --git a/src/lj_api.c b/src/lj_api.c
index 1f09284f..042b0d9c 100644
--- a/src/lj_api.c
+++ b/src/lj_api.c
@@ -1188,6 +1188,9 @@ LUA_API int lua_gc(lua_State *L, int what, int data)
     res = (int)(g->gc.stepmul);
     g->gc.stepmul = (MSize)data;
     break;
+  case LUA_GCISRUNNING:
+    res = (g->gc.threshold != LJ_MAX_MEM);
+    break;
   default:
     res = -1;  /* Invalid option. */
   }
diff --git a/src/lua.h b/src/lua.h
index c83fd3bb..352d29f3 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -226,6 +226,7 @@ LUA_API int  (lua_status) (lua_State *L);
 #define LUA_GCSTEP              5
 #define LUA_GCSETPAUSE          6
 #define LUA_GCSETSTEPMUL        7
+#define LUA_GCISRUNNING         9
 
 LUA_API int (lua_gc) (lua_State *L, int what, int data);