Function singlestep

src/Chain/libraries/glua/lgc.cpp:1048–1101

static lu_mem singlestep(lua_State *L) {
    global_State *g = G(L);
    switch (g->gcstate) {
    case GCSpause: {
        g->GCmemtrav = g->strt.size * sizeof(GCObject*);
        restartcollection(g);
        g->gcstate = GCSpropagate;
        return g->GCmemtrav;
    }
    case GCSpropagate: {
        g->GCmemtrav = 0;
        lua_assert(g->gray);
        propagatemark(g);
        if (g->gray == nullptr)  /* no more gray objects? */
            g->gcstate = GCSatomic;  /* finish propagate phase */
        return g->GCmemtrav;  /* memory traversed in this step */
    }
    case GCSatomic: {
        lu_mem work;
        int sw;
        propagateall(g);  /* make sure gray list is empty */
        work = atomic(L);  /* work is what was traversed by 'atomic' */
        sw = entersweep(L);
        g->GCestimate = gettotalbytes(g);  /* first estimate */;
        return work + sw * GCSWEEPCOST;
    }
    case GCSswpallgc: {  /* sweep "regular" objects */
        return sweepstep(L, g, GCSswpfinobj, &g->finobj);
    }
    case GCSswpfinobj: {  /* sweep objects with finalizers */
        return sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
    }
    case GCSswptobefnz: {  /* sweep objects to be finalized */
        return sweepstep(L, g, GCSswpend, nullptr);
    }
    case GCSswpend: {  /* finish sweeps */
        makewhite(g, g->mainthread);  /* sweep main thread */
        checkSizes(L, g);
        g->gcstate = GCScallfin;
        return 0;
    }
    case GCScallfin: {  /* call remaining finalizers */
        if (g->tobefnz && g->gckind != KGC_EMERGENCY) {
            int n = runafewfinalizers(L);
            return (n * GCFINALIZECOST);
        }
        else {  /* emergency mode or no more finalizers */
            g->gcstate = GCSpause;  /* finish collection */
            return 0;
        }
    }
    default: lua_assert(0); return 0;
    }
}


/*