isblack
lua_assert(!isblack(o) && uv->v != &uv->u.value);
lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o));
lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE);
lua_assert(isblack(obj2gco(p)));
lua_assert(!isblack(o)); /* open upvalues are never black */
#define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \
#define luaC_barrierback(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p))) \
{ if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \
{ if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) luaC_barrierback_(L,p); }
{ if (isblack(obj2gco(p))) luaC_barrierproto_(L,p,c); }