Threads are created like other objects

Using a version of 'luaC_newobj' that allows offsets (extra space
before the object itself).

lgc.c

@@ -252,12 +252,13 @@ void luaC_fix (lua_State *L, GCObject *o) {
 
 
 /*
-** create a new collectable object (with given type and size) and link
-** it to 'allgc' list.
+** create a new collectable object (with given type, size, and offset)
+** and link it to 'allgc' list.
 */
-GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
+GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
   global_State *g = G(L);
-  GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz));
+  char *p = cast_charp(luaM_newobject(L, novariant(tt), sz));
+  GCObject *o = cast(GCObject *, p + offset);
   o->marked = luaC_white(g);
   o->tt = tt;
   o->next = g->allgc;
@@ -265,6 +266,11 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
   return o;
 }
 
+
+GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
+  return luaC_newobjdt(L, tt, sz, 0);
+}
+
 /* }====================================================== */
 
 

lgc.h

@@ -190,6 +190,8 @@ LUAI_FUNC void luaC_step (lua_State *L);
 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
+LUAI_FUNC GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz,
+                                                 size_t offset);
 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
 LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);

lstate.c

@@ -284,18 +284,14 @@ static void close_state (lua_State *L) {
 
 
 LUA_API lua_State *lua_newthread (lua_State *L) {
-  global_State *g;
+  global_State *g = G(L);
+  GCObject *o;
   lua_State *L1;
   lua_lock(L);
-  g = G(L);
   luaC_checkGC(L);
   /* create new thread */
-  L1 = &cast(LX *, luaM_newobject(L, LUA_TTHREAD, sizeof(LX)))->l;
-  L1->marked = luaC_white(g);
-  L1->tt = LUA_VTHREAD;
-  /* link it on list 'allgc' */
-  L1->next = g->allgc;
-  g->allgc = obj2gco(L1);
+  o = luaC_newobjdt(L, LUA_TTHREAD, sizeof(LX), offsetof(LX, l));
+  L1 = gco2th(o);
   /* anchor it on L stack */
   setthvalue2s(L, L->top.p, L1);
   api_incr_top(L);