KGC_GEN
if (g->gckind == KGC_GEN) { /* generational mode? */
luaC_changemode(L, KGC_GEN);
if (origkind == KGC_GEN) { /* generational mode? */
if (mode == KGC_GEN) { /* change to generational mode */
g->gckind = KGC_GEN;
#define isgenerational(g) ((g)->gckind == KGC_GEN)