Function singlestep

Source/Misc/lua/src/lua.c:6558–6609

static l_mem singlestep (lua_State *L) {
global_State *g = G(L);
/*lua_checkmemory(L);*/
switch (g->gcstate) {
case GCSpause: {
markroot(L);  /* start a new collection */
return 0;
}
case GCSpropagate: {
if (g->gray)
return propagatemark(g);
else {  /* no more `gray' objects */
atomic(L);  /* finish mark phase */
return 0;
}
}
case GCSsweepstring: {
lu_mem old = g->totalbytes;
sweepwholelist(L, &g->strt.hash[g->sweepstrgc++]);
if (g->sweepstrgc >= g->strt.size)  /* nothing more to sweep? */
g->gcstate = GCSsweep;  /* end sweep-string phase */
lua_assert(old >= g->totalbytes);
g->estimate -= old - g->totalbytes;
return GCSWEEPCOST;
}
case GCSsweep: {
lu_mem old = g->totalbytes;
g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
if (*g->sweepgc == NULL) {  /* nothing more to sweep? */
checkSizes(L);
g->gcstate = GCSfinalize;  /* end sweep phase */
}
lua_assert(old >= g->totalbytes);
g->estimate -= old - g->totalbytes;
return GCSWEEPMAX*GCSWEEPCOST;
}
case GCSfinalize: {
if (g->tmudata) {
GCTM(L);
if (g->estimate > GCFINALIZECOST)
g->estimate -= GCFINALIZECOST;
return GCFINALIZECOST;
}
else {
g->gcstate = GCSpause;  /* end collection */
g->gcdept = 0;
return 0;
}
}
default: lua_assert(0); return 0;
}
}


void luaC_step (lua_State *L) {