41 files changed, 787 insertions, 791 deletions

diff --git a/lapi.c b/lapi.c
index 34e64af1..a1eb7dc6 100644
--- a/lapi.c
+++ b/lapi.c
@@ -1107,16 +1107,37 @@ LUA_API int lua_load (lua_State *L, lua_Reader reader, void *data,
 }
 
 
+/*
+** Dump a function, calling 'writer' to write its parts. Because the
+** writer can use the stack in unkown ways, this function should not
+** push things on the stack, but it must anchor an auxiliary table
+** used by 'luaU_dump'. To do so, it creates the table, anchors the
+** function that is on the stack in the table, and substitutes the
+** table for the function in the stack.
+*/
+
 LUA_API int lua_dump (lua_State *L, lua_Writer writer, void *data, int strip) {
   int status;
+  StkId fstk;  /* pointer to function */
   TValue *o;
   lua_lock(L);
   api_checknelems(L, 1);
-  o = s2v(L->top.p - 1);
-  if (isLfunction(o))
-    status = luaU_dump(L, getproto(o), writer, data, strip);
-  else
+  fstk = L->top.p - 1;
+  o = s2v(fstk);
+  if (!isLfunction(o))
     status = 1;
+  else {
+    LClosure *f = clLvalue(o);
+    ptrdiff_t fidx = savestack(L, fstk);  /* function index */
+    Table *h = luaH_new(L);  /* auxiliary table used by 'luaU_dump' */
+    sethvalue2s(L, L->top.p, h);  /* anchor it (luaH_set may call GC) */
+    L->top.p++;  /* (assume extra slot) */
+    luaH_set(L, h, o, o);  /* anchor function into table */
+    setobjs2s(L, fstk, L->top.p - 1);  /* move table over function */
+    L->top.p--;  /* stack back to initial size */
+    status = luaU_dump(L, f->p, writer, data, strip, h);
+    setclLvalue2s(L, restorestack(L, fidx), f);  /* put function back */
+  }
   lua_unlock(L);
   return status;
 }
@@ -1145,7 +1166,7 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
     }
     case LUA_GCRESTART: {
       luaE_setdebt(g, 0);
-      g->gcstp = 0;  /* (GCSTPGC must be already zero here) */
+      g->gcstp = 0;  /* (bit GCSTPGC must be zero here) */
       break;
     }
     case LUA_GCCOLLECT: {
@@ -1154,42 +1175,46 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
     }
     case LUA_GCCOUNT: {
       /* GC values are expressed in Kbytes: #bytes/2^10 */
-      res = cast_int(gettotalbytes(g) >> 10);
+      res = cast_int(g->totalbytes >> 10);
       break;
     }
     case LUA_GCCOUNTB: {
-      res = cast_int(gettotalbytes(g) & 0x3ff);
+      res = cast_int(g->totalbytes & 0x3ff);
       break;
     }
     case LUA_GCSTEP: {
-      int data = va_arg(argp, int);
-      l_mem debt = 1;  /* =1 to signal that it did an actual step */
+      int todo = va_arg(argp, int);  /* work to be done */
+      int didsomething = 0;
       lu_byte oldstp = g->gcstp;
-      g->gcstp = 0;  /* allow GC to run (GCSTPGC must be zero here) */
-      if (data == 0) {
-        luaE_setdebt(g, 0);  /* do a basic step */
-        luaC_step(L);
-      }
-      else {  /* add 'data' to total debt */
-        debt = cast(l_mem, data) * 1024 + g->GCdebt;
-        luaE_setdebt(g, debt);
-        luaC_checkGC(L);
+      g->gcstp = 0;  /* allow GC to run (bit GCSTPGC must be zero here) */
+      if (todo == 0)
+        todo = 1 << g->gcstepsize;  /* standard step size */
+      while (todo >= g->GCdebt) {  /* enough to run a step? */
+        todo -= g->GCdebt;  /* decrement 'todo' */
+        luaC_step(L);  /* run one basic step */
+        didsomething = 1;
+        if (g->gckind == KGC_GEN)  /* minor collections? */
+          todo = 0;  /* doesn't make sense to repeat in this case */
+        else if (g->gcstate == GCSpause)
+          break;  /* don't run more than one cycle */
       }
+      /* remove remaining 'todo' from total debt */
+      luaE_setdebt(g, g->GCdebt - todo);
       g->gcstp = oldstp;  /* restore previous state */
-      if (debt > 0 && g->gcstate == GCSpause)  /* end of cycle? */
+      if (didsomething && g->gcstate == GCSpause)  /* end of cycle? */
         res = 1;  /* signal it */
       break;
     }
     case LUA_GCSETPAUSE: {
-      int data = va_arg(argp, int);
-      res = getgcparam(g->gcpause);
-      setgcparam(g->gcpause, data);
+      unsigned int data = va_arg(argp, unsigned int);
+      res = applygcparam(g, gcpause, 100);
+      setgcparam(g, gcpause, data);
       break;
     }
     case LUA_GCSETSTEPMUL: {
-      int data = va_arg(argp, int);
-      res = getgcparam(g->gcstepmul);
-      setgcparam(g->gcstepmul, data);
+      unsigned int data = va_arg(argp, unsigned int);
+      res = applygcparam(g, gcstepmul, 100);
+      setgcparam(g, gcstepmul, data);
       break;
     }
     case LUA_GCISRUNNING: {
@@ -1197,27 +1222,28 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
       break;
     }
     case LUA_GCGEN: {
-      int minormul = va_arg(argp, int);
-      int majormul = va_arg(argp, int);
-      res = isdecGCmodegen(g) ? LUA_GCGEN : LUA_GCINC;
+      unsigned int minormul = va_arg(argp, unsigned int);
+      unsigned int majormul = va_arg(argp, unsigned int);
+      res = (g->gckind == KGC_INC) ? LUA_GCINC : LUA_GCGEN;
       if (minormul != 0)
-        g->genminormul = minormul;
+        setgcparam(g, genminormul, minormul);
       if (majormul != 0)
-        setgcparam(g->genmajormul, majormul);
+        setgcparam(g, genmajormul, majormul);
       luaC_changemode(L, KGC_GEN);
       break;
     }
     case LUA_GCINC: {
-      int pause = va_arg(argp, int);
-      int stepmul = va_arg(argp, int);
-      int stepsize = va_arg(argp, int);
-      res = isdecGCmodegen(g) ? LUA_GCGEN : LUA_GCINC;
+      unsigned int pause = va_arg(argp, unsigned int);
+      unsigned int stepmul = va_arg(argp, unsigned int);
+      unsigned int stepsize = va_arg(argp, unsigned int);
+      res = (g->gckind == KGC_INC) ? LUA_GCINC : LUA_GCGEN;
       if (pause != 0)
-        setgcparam(g->gcpause, pause);
+        setgcparam(g, gcpause, pause);
       if (stepmul != 0)
-        setgcparam(g->gcstepmul, stepmul);
+        setgcparam(g, gcstepmul, stepmul);
       if (stepsize != 0)
-        g->gcstepsize = stepsize;
+        g->gcstepsize = (stepsize <= log2maxs(l_obj)) ? stepsize
+                                                      : log2maxs(l_obj);
       luaC_changemode(L, KGC_INC);
       break;
     }
@@ -1285,13 +1311,14 @@ LUA_API void lua_toclose (lua_State *L, int idx) {
 LUA_API void lua_concat (lua_State *L, int n) {
   lua_lock(L);
   api_checknelems(L, n);
-  if (n > 0)
+  if (n > 0) {
     luaV_concat(L, n);
+    luaC_checkGC(L);
+  }
   else {  /* nothing to concatenate */
     setsvalue2s(L, L->top.p, luaS_newlstr(L, "", 0));  /* push empty string */
     api_incr_top(L);
   }
-  luaC_checkGC(L);
   lua_unlock(L);
 }
 
diff --git a/lauxlib.c b/lauxlib.c
index 4ca6c654..555a5976 100644
--- a/lauxlib.c
+++ b/lauxlib.c
@@ -1091,8 +1091,54 @@ static void warnfon (void *ud, const char *message, int tocont) {
 }
 
 
+
+/*
+** A function to compute an unsigned int with some level of
+** randomness. Rely on Address Space Layout Randomization (if present)
+** and the current time.
+*/
+#if !defined(luai_makeseed)
+
+#include <time.h>
+
+
+/*
+** Size of 'e' measured in number of 'unsigned int's. (In the weird
+** case that the division truncates, we just lose some part of the
+** value, no big deal.)
+*/
+#define sof(e)          (sizeof(e) / sizeof(unsigned int))
+
+
+#define addbuff(b,v) \
+        (memcpy(b, &(v), sof(v) * sizeof(unsigned int)), b += sof(v))
+
+
+static unsigned int luai_makeseed (void) {
+  unsigned int buff[sof(void*) + sof(time_t)];
+  unsigned int res;
+  unsigned int *b = buff;
+  time_t t = time(NULL);
+  void *h = buff;
+  addbuff(b, h);  /* local variable's address */
+  addbuff(b, t);  /* time */
+  res = buff[0];
+  for (b = buff + 1; b < buff + sof(buff); b++)
+    res ^= (res >> 3) + (res << 7) + *b;
+  return res;
+}
+
+#endif
+
+
+LUALIB_API unsigned int luaL_makeseed (lua_State *L) {
+  (void)L;  /* unused */
+  return luai_makeseed();
+}
+
+
 LUALIB_API lua_State *luaL_newstate (void) {
-  lua_State *L = lua_newstate(l_alloc, NULL);
+  lua_State *L = lua_newstate(l_alloc, NULL, luai_makeseed());
   if (l_likely(L)) {
     lua_atpanic(L, &panic);
     lua_setwarnf(L, warnfoff, L);  /* default is warnings off */
diff --git a/lauxlib.h b/lauxlib.h
index 5b977e2a..0ee9a572 100644
--- a/lauxlib.h
+++ b/lauxlib.h
@@ -100,6 +100,8 @@ LUALIB_API int (luaL_loadstring) (lua_State *L, const char *s);
 
 LUALIB_API lua_State *(luaL_newstate) (void);
 
+LUALIB_API unsigned int luaL_makeseed (lua_State *L);
+
 LUALIB_API lua_Integer (luaL_len) (lua_State *L, int idx);
 
 LUALIB_API void (luaL_addgsub) (luaL_Buffer *b, const char *s,
diff --git a/ldo.c b/ldo.c
index bd8d965f..3df6a4b8 100644
--- a/ldo.c
+++ b/ldo.c
@@ -412,7 +412,7 @@ static void rethook (lua_State *L, CallInfo *ci, int nres) {
 static StkId tryfuncTM (lua_State *L, StkId func) {
   const TValue *tm;
   StkId p;
-  checkstackGCp(L, 1, func);  /* space for metamethod */
+  checkstackp(L, 1, func);  /* space for metamethod */
   tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);  /* (after previous GC) */
   if (l_unlikely(ttisnil(tm)))
     luaG_callerror(L, s2v(func));  /* nothing to call */
@@ -517,7 +517,7 @@ l_sinline int precallC (lua_State *L, StkId func, int nresults,
                                             lua_CFunction f) {
   int n;  /* number of returns */
   CallInfo *ci;
-  checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+  checkstackp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
   L->ci = ci = prepCallInfo(L, func, nresults, CIST_C,
                                L->top.p + LUA_MINSTACK);
   lua_assert(ci->top.p <= L->stack_last.p);
@@ -553,7 +553,7 @@ int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
       int fsize = p->maxstacksize;  /* frame size */
       int nfixparams = p->numparams;
       int i;
-      checkstackGCp(L, fsize - delta, func);
+      checkstackp(L, fsize - delta, func);
       ci->func.p -= delta;  /* restore 'func' (if vararg) */
       for (i = 0; i < narg1; i++)  /* move down function and arguments */
         setobjs2s(L, ci->func.p + i, func + i);
@@ -600,7 +600,7 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
       int narg = cast_int(L->top.p - func) - 1;  /* number of real arguments */
       int nfixparams = p->numparams;
       int fsize = p->maxstacksize;  /* frame size */
-      checkstackGCp(L, fsize, func);
+      checkstackp(L, fsize, func);
       L->ci = ci = prepCallInfo(L, func, nresults, 0, func + 1 + fsize);
       ci->u.l.savedpc = p->code;  /* starting point */
       for (; narg < nfixparams; narg++)
diff --git a/ldo.h b/ldo.h
index 56008ab3..4bc75030 100644
--- a/ldo.h
+++ b/ldo.h
@@ -44,18 +44,6 @@
     p = restorestack(L, t__))  /* 'pos' part: restore 'p' */
 
 
-/* macro to check stack size and GC, preserving 'p' */
-#define checkstackGCp(L,n,p)  \
-  luaD_checkstackaux(L, n, \
-    ptrdiff_t t__ = savestack(L, p);  /* save 'p' */ \
-    luaC_checkGC(L),  /* stack grow uses memory */ \
-    p = restorestack(L, t__))  /* 'pos' part: restore 'p' */
-
-
-/* macro to check stack size and GC */
-#define checkstackGC(L,fsize)  \
-        luaD_checkstackaux(L, (fsize), luaC_checkGC(L), (void)0)
-
 
 /* type of protected functions, to be ran by 'runprotected' */
 typedef void (*Pfunc) (lua_State *L, void *ud);
diff --git a/ldump.c b/ldump.c
index f231691b..3e91190c 100644
--- a/ldump.c
+++ b/ldump.c
@@ -15,8 +15,10 @@
 
 #include "lua.h"
 
+#include "lgc.h"
 #include "lobject.h"
 #include "lstate.h"
+#include "ltable.h"
 #include "lundump.h"
 
 
@@ -26,6 +28,8 @@ typedef struct {
   void *data;
   int strip;
   int status;
+  Table *h;  /* table to track saved strings */
+  lua_Integer nstr;  /* counter to number saved strings */
 } DumpState;
 
 
@@ -89,14 +93,33 @@ static void dumpInteger (DumpState *D, lua_Integer x) {
 }
 
 
-static void dumpString (DumpState *D, const TString *s) {
+/*
+** Dump a String. First dump its "size": size==0 means NULL;
+** size==1 is followed by an index and means "reuse saved string with
+** that index"; size>=2 is followed by the string contents with real
+** size==size-2 and means that string, which will be saved with
+** the next available index.
+*/
+static void dumpString (DumpState *D, TString *s) {
   if (s == NULL)
     dumpSize(D, 0);
   else {
-    size_t size = tsslen(s);
-    const char *str = getstr(s);
-    dumpSize(D, size + 1);
-    dumpVector(D, str, size);
+    const TValue *idx = luaH_getstr(D->h, s);
+    if (ttisinteger(idx)) {  /* string already saved? */
+      dumpSize(D, 1);  /* reuse a saved string */
+      dumpInt(D, ivalue(idx));  /* index of saved string */
+    }
+    else {  /* must write and save the string */
+      TValue key, value;  /* to save the string in the hash */
+      size_t size = tsslen(s);
+      dumpSize(D, size + 2);
+      dumpVector(D, getstr(s), size);
+      D->nstr++;  /* one more saved string */
+      setsvalue(D->L, &key, s);  /* the string is the key */
+      setivalue(&value, D->nstr);  /* its index is the value */
+      luaH_finishset(D->L, D->h, &key, idx, &value);  /* h[s] = nstr */
+      /* integer value does not need barrier */
+    }
   }
 }
 
@@ -107,7 +130,7 @@ static void dumpCode (DumpState *D, const Proto *f) {
 }
 
 
-static void dumpFunction(DumpState *D, const Proto *f, TString *psource);
+static void dumpFunction(DumpState *D, const Proto *f);
 
 static void dumpConstants (DumpState *D, const Proto *f) {
   int i;
@@ -140,7 +163,7 @@ static void dumpProtos (DumpState *D, const Proto *f) {
   int n = f->sizep;
   dumpInt(D, n);
   for (i = 0; i < n; i++)
-    dumpFunction(D, f->p[i], f->source);
+    dumpFunction(D, f->p[i]);
 }
 
 
@@ -180,9 +203,9 @@ static void dumpDebug (DumpState *D, const Proto *f) {
 }
 
 
-static void dumpFunction (DumpState *D, const Proto *f, TString *psource) {
-  if (D->strip || f->source == psource)
-    dumpString(D, NULL);  /* no debug info or same source as its parent */
+static void dumpFunction (DumpState *D, const Proto *f) {
+  if (D->strip)
+    dumpString(D, NULL);  /* no debug info */
   else
     dumpString(D, f->source);
   dumpInt(D, f->linedefined);
@@ -215,16 +238,18 @@ static void dumpHeader (DumpState *D) {
 ** dump Lua function as precompiled chunk
 */
 int luaU_dump(lua_State *L, const Proto *f, lua_Writer w, void *data,
-              int strip) {
+              int strip, Table *h) {
   DumpState D;
   D.L = L;
   D.writer = w;
   D.data = data;
   D.strip = strip;
   D.status = 0;
+  D.h = h;
+  D.nstr = 0;
   dumpHeader(&D);
   dumpByte(&D, f->sizeupvalues);
-  dumpFunction(&D, f, NULL);
+  dumpFunction(&D, f);
   return D.status;
 }
 
diff --git a/lgc.c b/lgc.c
index dd824e77..f68c5af0 100644
--- a/lgc.c
+++ b/lgc.c
@@ -9,7 +9,6 @@
 
 #include "lprefix.h"
 
-#include <stdio.h>
 #include <string.h>
 
 
@@ -19,6 +18,7 @@
 #include "ldo.h"
 #include "lfunc.h"
 #include "lgc.h"
+#include "llex.h"
 #include "lmem.h"
 #include "lobject.h"
 #include "lstate.h"
@@ -28,36 +28,18 @@
 
 
 /*
-** Maximum number of elements to sweep in each single step.
-** (Large enough to dissipate fixed overheads but small enough
-** to allow small steps for the collector.)
-*/
-#define GCSWEEPMAX      100
-
-/*
-** Maximum number of finalizers to call in each single step.
-*/
-#define GCFINMAX        10
-
-
-/*
-** Cost of calling one finalizer.
-*/
-#define GCFINALIZECOST  50
-
-
-/*
-** The equivalent, in bytes, of one unit of "work" (visiting a slot,
-** sweeping an object, etc.)
+** Number of fixed (luaC_fix) objects in a Lua state: metafield names,
+** plus reserved words, plus "_ENV", plus the memory-error message.
 */
-#define WORK2MEM        sizeof(TValue)
+#define NFIXED          (TM_N + NUM_RESERVED + 2)
 
 
 /*
-** macro to adjust 'pause': 'pause' is actually used like
-** 'pause / PAUSEADJ' (value chosen by tests)
+** Maximum number of elements to sweep in each single step.
+** (Large enough to dissipate fixed overheads but small enough
+** to allow small steps for the collector.)
 */
-#define PAUSEADJ                100
+#define GCSWEEPMAX      20
 
 
 /* mask with all color bits */
@@ -105,7 +87,7 @@
 #define markobjectN(g,t)        { if (t) markobject(g,t); }
 
 static void reallymarkobject (global_State *g, GCObject *o);
-static lu_mem atomic (lua_State *L);
+static l_obj atomic (lua_State *L);
 static void entersweep (lua_State *L);
 
 
@@ -217,7 +199,7 @@ void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) {
   }
   else {  /* sweep phase */
     lua_assert(issweepphase(g));
-    if (g->gckind == KGC_INC)  /* incremental mode? */
+    if (g->gckind != KGC_GEN)  /* incremental mode? */
       makewhite(g, o);  /* mark 'o' as white to avoid other barriers */
   }
 }
@@ -259,6 +241,7 @@ GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
   global_State *g = G(L);
   char *p = cast_charp(luaM_newobject(L, novariant(tt), sz));
   GCObject *o = cast(GCObject *, p + offset);
+  g->GCdebt--;
   o->marked = luaC_white(g);
   o->tt = tt;
   o->next = g->allgc;
@@ -267,6 +250,9 @@ GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
 }
 
 
+/*
+** create a new collectable object with no offset.
+*/
 GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
   return luaC_newobjdt(L, tt, sz, 0);
 }
@@ -295,6 +281,7 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
 ** (only closures can), and a userdata's metatable must be a table.
 */
 static void reallymarkobject (global_State *g, GCObject *o) {
+  g->marked++;
   switch (o->tt) {
     case LUA_VSHRSTR:
     case LUA_VLNGSTR: {
@@ -342,9 +329,9 @@ static void markmt (global_State *g) {
 /*
 ** mark all objects in list of being-finalized
 */
-static lu_mem markbeingfnz (global_State *g) {
+static l_obj markbeingfnz (global_State *g) {
   GCObject *o;
-  lu_mem count = 0;
+  l_obj count = 0;
   for (o = g->tobefnz; o != NULL; o = o->next) {
     count++;
     markobject(g, o);
@@ -364,12 +351,11 @@ static lu_mem markbeingfnz (global_State *g) {
 ** upvalues, as they have nothing to be checked. (If the thread gets an
 ** upvalue later, it will be linked in the list again.)
 */
-static int remarkupvals (global_State *g) {
+static l_obj remarkupvals (global_State *g) {
+  l_obj work = 0;
   lua_State *thread;
   lua_State **p = &g->twups;
-  int work = 0;  /* estimate of how much work was done here */
   while ((thread = *p) != NULL) {
-    work++;
     if (!iswhite(thread) && thread->openupval != NULL)
       p = &thread->twups;  /* keep marked thread with upvalues in the list */
     else {  /* thread is not marked or without upvalues */
@@ -379,13 +365,13 @@ static int remarkupvals (global_State *g) {
       thread->twups = thread;  /* mark that it is out of list */
       for (uv = thread->openupval; uv != NULL; uv = uv->u.open.next) {
         lua_assert(getage(uv) <= getage(thread));
-        work++;
         if (!iswhite(uv)) {  /* upvalue already visited? */
           lua_assert(upisopen(uv) && isgray(uv));
           markvalue(g, uv->v.p);  /* mark its value */
         }
       }
     }
+    work++;
   }
   return work;
 }
@@ -398,10 +384,15 @@ static void cleargraylists (global_State *g) {
 
 
 /*
-** mark root set and reset all gray lists, to start a new collection
+** mark root set and reset all gray lists, to start a new collection.
+** 'marked' is initialized with the number of fixed objects in the state,
+** to count the total number of live objects during a cycle. (That is
+** the metafield names, plus the reserved words, plus "_ENV" plus the
+** memory-error message.)
 */
 static void restartcollection (global_State *g) {
   cleargraylists(g);
+  g->marked = NFIXED;
   markobject(g, g->mainthread);
   markvalue(g, &g->l_registry);
   markmt(g);
@@ -539,7 +530,7 @@ static void traversestrongtable (global_State *g, Table *h) {
 }
 
 
-static lu_mem traversetable (global_State *g, Table *h) {
+static void traversetable (global_State *g, Table *h) {
   const char *weakkey, *weakvalue;
   const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
   markobjectN(g, h->metatable);
@@ -556,17 +547,15 @@ static lu_mem traversetable (global_State *g, Table *h) {
   }
   else  /* not weak */
     traversestrongtable(g, h);
-  return 1 + h->alimit + 2 * allocsizenode(h);
 }
 
 
-static int traverseudata (global_State *g, Udata *u) {
+static void traverseudata (global_State *g, Udata *u) {
   int i;
   markobjectN(g, u->metatable);  /* mark its metatable */
   for (i = 0; i < u->nuvalue; i++)
     markvalue(g, &u->uv[i].uv);
   genlink(g, obj2gco(u));
-  return 1 + u->nuvalue;
 }
 
 
@@ -575,7 +564,7 @@ static int traverseudata (global_State *g, Udata *u) {
 ** arrays can be larger than needed; the extra slots are filled with
 ** NULL, so the use of 'markobjectN')
 */
-static int traverseproto (global_State *g, Proto *f) {
+static void traverseproto (global_State *g, Proto *f) {
   int i;
   markobjectN(g, f->source);
   for (i = 0; i < f->sizek; i++)  /* mark literals */
@@ -586,29 +575,26 @@ static int traverseproto (global_State *g, Proto *f) {
     markobjectN(g, f->p[i]);
   for (i = 0; i < f->sizelocvars; i++)  /* mark local-variable names */
     markobjectN(g, f->locvars[i].varname);
-  return 1 + f->sizek + f->sizeupvalues + f->sizep + f->sizelocvars;
 }
 
 
-static int traverseCclosure (global_State *g, CClosure *cl) {
+static void traverseCclosure (global_State *g, CClosure *cl) {
   int i;
   for (i = 0; i < cl->nupvalues; i++)  /* mark its upvalues */
     markvalue(g, &cl->upvalue[i]);
-  return 1 + cl->nupvalues;
 }
 
 /*
 ** Traverse a Lua closure, marking its prototype and its upvalues.
 ** (Both can be NULL while closure is being created.)
 */
-static int traverseLclosure (global_State *g, LClosure *cl) {
+static void traverseLclosure (global_State *g, LClosure *cl) {
   int i;
   markobjectN(g, cl->p);  /* mark its prototype */
   for (i = 0; i < cl->nupvalues; i++) {  /* visit its upvalues */
     UpVal *uv = cl->upvals[i];
     markobjectN(g, uv);  /* mark upvalue */
   }
-  return 1 + cl->nupvalues;
 }
 
 
@@ -624,13 +610,13 @@ static int traverseLclosure (global_State *g, LClosure *cl) {
 ** (which can only happen in generational mode) or if the traverse is in
 ** the propagate phase (which can only happen in incremental mode).
 */
-static int traversethread (global_State *g, lua_State *th) {
+static void traversethread (global_State *g, lua_State *th) {
   UpVal *uv;
   StkId o = th->stack.p;
   if (isold(th) || g->gcstate == GCSpropagate)
     linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
   if (o == NULL)
-    return 1;  /* stack not completely built yet */
+    return;  /* stack not completely built yet */
   lua_assert(g->gcstate == GCSatomic ||
              th->openupval == NULL || isintwups(th));
   for (; o < th->top.p; o++)  /* mark live elements in the stack */
@@ -648,34 +634,35 @@ static int traversethread (global_State *g, lua_State *th) {
   }
   else if (!g->gcemergency)
     luaD_shrinkstack(th); /* do not change stack in emergency cycle */
-  return 1 + stacksize(th);
 }
 
 
 /*
 ** traverse one gray object, turning it to black.
 */
-static lu_mem propagatemark (global_State *g) {
+static void propagatemark (global_State *g) {
   GCObject *o = g->gray;
   nw2black(o);
   g->gray = *getgclist(o);  /* remove from 'gray' list */
   switch (o->tt) {
-    case LUA_VTABLE: return traversetable(g, gco2t(o));
-    case LUA_VUSERDATA: return traverseudata(g, gco2u(o));
-    case LUA_VLCL: return traverseLclosure(g, gco2lcl(o));
-    case LUA_VCCL: return traverseCclosure(g, gco2ccl(o));
-    case LUA_VPROTO: return traverseproto(g, gco2p(o));
-    case LUA_VTHREAD: return traversethread(g, gco2th(o));
-    default: lua_assert(0); return 0;
+    case LUA_VTABLE: traversetable(g, gco2t(o)); break;
+    case LUA_VUSERDATA: traverseudata(g, gco2u(o)); break;
+    case LUA_VLCL: traverseLclosure(g, gco2lcl(o)); break;
+    case LUA_VCCL: traverseCclosure(g, gco2ccl(o)); break;
+    case LUA_VPROTO: traverseproto(g, gco2p(o)); break;
+    case LUA_VTHREAD: traversethread(g, gco2th(o)); break;
+    default: lua_assert(0);
   }
 }
 
 
-static lu_mem propagateall (global_State *g) {
-  lu_mem tot = 0;
-  while (g->gray)
-    tot += propagatemark(g);
-  return tot;
+static l_obj propagateall (global_State *g) {
+  l_obj work = 0;
+  while (g->gray) {
+    propagatemark(g);
+    work++;
+  }
+  return work;
 }
 
 
@@ -684,10 +671,10 @@ static lu_mem propagateall (global_State *g) {
 ** Repeat until it converges, that is, nothing new is marked. 'dir'
 ** inverts the direction of the traversals, trying to speed up
 ** convergence on chains in the same table.
-**
 */
-static void convergeephemerons (global_State *g) {
+static l_obj convergeephemerons (global_State *g) {
   int changed;
+  l_obj work = 0;
   int dir = 0;
   do {
     GCObject *w;
@@ -702,9 +689,11 @@ static void convergeephemerons (global_State *g) {
         propagateall(g);  /* propagate changes */
         changed = 1;  /* will have to revisit all ephemeron tables */
       }
+      work++;
     }
     dir = !dir;  /* invert direction next time */
   } while (changed);  /* repeat until no more changes */
+  return work;
 }
 
 /* }====================================================== */
@@ -720,7 +709,8 @@ static void convergeephemerons (global_State *g) {
 /*
 ** clear entries with unmarked keys from all weaktables in list 'l'
 */
-static void clearbykeys (global_State *g, GCObject *l) {
+static l_obj clearbykeys (global_State *g, GCObject *l) {
+  l_obj work = 0;
   for (; l; l = gco2t(l)->gclist) {
     Table *h = gco2t(l);
     Node *limit = gnodelast(h);
@@ -731,7 +721,9 @@ static void clearbykeys (global_State *g, GCObject *l) {
       if (isempty(gval(n)))  /* is entry empty? */
         clearkey(n);  /* clear its key */
     }
+    work++;
   }
+  return work;
 }
 
 
@@ -739,7 +731,8 @@ static void clearbykeys (global_State *g, GCObject *l) {
 ** clear entries with unmarked values from all weaktables in list 'l' up
 ** to element 'f'
 */
-static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
+static l_obj clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
+  l_obj work = 0;
   for (; l != f; l = gco2t(l)->gclist) {
     Table *h = gco2t(l);
     Node *n, *limit = gnodelast(h);
@@ -756,7 +749,9 @@ static void clearbyvalues (global_State *g, GCObject *l, GCObject *f) {
       if (isempty(gval(n)))  /* is entry empty? */
         clearkey(n);  /* clear its key */
     }
+    work++;
   }
+  return work;
 }
 
 
@@ -768,6 +763,7 @@ static void freeupval (lua_State *L, UpVal *uv) {
 
 
 static void freeobj (lua_State *L, GCObject *o) {
+  G(L)->totalobjs--;
   switch (o->tt) {
     case LUA_VPROTO:
       luaF_freeproto(L, gco2p(o));
@@ -817,10 +813,9 @@ static void freeobj (lua_State *L, GCObject *o) {
 ** objects, where a dead object is one marked with the old (non current)
 ** white; change all non-dead objects back to white, preparing for next
 ** collection cycle. Return where to continue the traversal or NULL if
-** list is finished. ('*countout' gets the number of elements traversed.)
+** list is finished.
 */
-static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
-                             int *countout) {
+static GCObject **sweeplist (lua_State *L, GCObject **p, int countin) {
   global_State *g = G(L);
   int ow = otherwhite(g);
   int i;
@@ -837,8 +832,6 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
       p = &curr->next;  /* go to next element */
     }
   }
-  if (countout)
-    *countout = i;  /* number of elements traversed */
   return (*p == NULL) ? NULL : p;
 }
 
@@ -849,7 +842,7 @@ static GCObject **sweeplist (lua_State *L, GCObject **p, int countin,
 static GCObject **sweeptolive (lua_State *L, GCObject **p) {
   GCObject **old = p;
   do {
-    p = sweeplist(L, p, 1, NULL);
+    p = sweeplist(L, p, 1);
   } while (p == old);
   return p;
 }
@@ -868,11 +861,8 @@ static GCObject **sweeptolive (lua_State *L, GCObject **p) {
 */
 static void checkSizes (lua_State *L, global_State *g) {
   if (!g->gcemergency) {
-    if (g->strt.nuse < g->strt.size / 4) {  /* string table too big? */
-      l_mem olddebt = g->GCdebt;
+    if (g->strt.nuse < g->strt.size / 4)  /* string table too big? */
       luaS_resize(L, g->strt.size / 2);
-      g->GCestimate += g->GCdebt - olddebt;  /* correct estimate */
-    }
   }
 }
 
@@ -931,18 +921,6 @@ static void GCTM (lua_State *L) {
 
 
 /*
-** Call a few finalizers
-*/
-static int runafewfinalizers (lua_State *L, int n) {
-  global_State *g = G(L);
-  int i;
-  for (i = 0; i < n && g->tobefnz; i++)
-    GCTM(L);  /* call one finalizer */
-  return i;
-}
-
-
-/*
 ** call all pending finalizers
 */
 static void callallpendingfinalizers (lua_State *L) {
@@ -1050,20 +1028,13 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
 
 /*
 ** Set the "time" to wait before starting a new GC cycle; cycle will
-** start when memory use hits the threshold of ('estimate' * pause /
-** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero,
-** because Lua cannot even start with less than PAUSEADJ bytes).
+** start when number of objects in use hits the threshold of
+** approximately (marked * pause / 100).
 */
 static void setpause (global_State *g) {
-  l_mem threshold, debt;
-  int pause = getgcparam(g->gcpause);
-  l_mem estimate = g->GCestimate / PAUSEADJ;  /* adjust 'estimate' */
-  lua_assert(estimate > 0);
-  threshold = (pause < MAX_LMEM / estimate)  /* overflow? */
-            ? estimate * pause  /* no overflow */
-            : MAX_LMEM;  /* overflow; truncate to maximum */
-  debt = gettotalbytes(g) - threshold;
-  if (debt > 0) debt = 0;
+  l_obj threshold = applygcparam(g, gcpause, g->marked);
+  l_obj debt = threshold - gettotalobjs(g);
+  if (debt < 0) debt = 0;
   luaE_setdebt(g, debt);
 }
 
@@ -1303,18 +1274,17 @@ static void atomic2gen (lua_State *L, global_State *g) {
   sweep2old(L, &g->tobefnz);
 
   g->gckind = KGC_GEN;
-  g->lastatomic = 0;
-  g->GCestimate = gettotalbytes(g);  /* base for memory control */
+  g->GClastmajor = gettotalobjs(g);  /* base for memory control */
   finishgencycle(L, g);
 }
 
 
 /*
 ** Set debt for the next minor collection, which will happen when
-** memory grows 'genminormul'%.
+** total number of objects grows 'genminormul'%.
 */
 static void setminordebt (global_State *g) {
-  luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul));
+  luaE_setdebt(g, applygcparam(g, genminormul, gettotalobjs(g)));
 }
 
 
@@ -1324,14 +1294,12 @@ static void setminordebt (global_State *g) {
 ** are cleared. Then, turn all objects into old and finishes the
 ** collection.
 */
-static lu_mem entergen (lua_State *L, global_State *g) {
-  lu_mem numobjs;
+static void entergen (lua_State *L, global_State *g) {
   luaC_runtilstate(L, bitmask(GCSpause));  /* prepare to start a new cycle */
   luaC_runtilstate(L, bitmask(GCSpropagate));  /* start new cycle */
-  numobjs = atomic(L);  /* propagates all and then do the atomic stuff */
+  atomic(L);  /* propagates all and then do the atomic stuff */
   atomic2gen(L, g);
   setminordebt(g);  /* set debt assuming next cycle will be minor */
-  return numobjs;
 }
 
 
@@ -1348,7 +1316,6 @@ static void enterinc (global_State *g) {
   g->finobjrold = g->finobjold1 = g->finobjsur = NULL;
   g->gcstate = GCSpause;
   g->gckind = KGC_INC;
-  g->lastatomic = 0;
 }
 
 
@@ -1357,111 +1324,75 @@ static void enterinc (global_State *g) {
 */
 void luaC_changemode (lua_State *L, int newmode) {
   global_State *g = G(L);
-  if (newmode != g->gckind) {
-    if (newmode == KGC_GEN)  /* entering generational mode? */
+  if (newmode != g->gckind) {  /* does it need to change? */
+    if (newmode == KGC_INC) {  /* entering incremental mode? */
+      if (g->gckind == KGC_GENMAJOR)
+        g->gckind = KGC_INC;  /* already incremental but in name */
+      else
+        enterinc(g);  /* entering incremental mode */
+    }
+    else {
+      lua_assert(newmode == KGC_GEN);
       entergen(L, g);
-    else
-      enterinc(g);  /* entering incremental mode */
+    }
   }
-  g->lastatomic = 0;
 }
 
 
 /*
 ** Does a full collection in generational mode.
 */
-static lu_mem fullgen (lua_State *L, global_State *g) {
+static void fullgen (lua_State *L, global_State *g) {
   enterinc(g);
-  return entergen(L, g);
-}
-
-
-/*
-** Does a major collection after last collection was a "bad collection".
-**
-** When the program is building a big structure, it allocates lots of
-** memory but generates very little garbage. In those scenarios,
-** the generational mode just wastes time doing small collections, and
-** major collections are frequently what we call a "bad collection", a
-** collection that frees too few objects. To avoid the cost of switching
-** between generational mode and the incremental mode needed for full
-** (major) collections, the collector tries to stay in incremental mode
-** after a bad collection, and to switch back to generational mode only
-** after a "good" collection (one that traverses less than 9/8 objects
-** of the previous one).
-** The collector must choose whether to stay in incremental mode or to
-** switch back to generational mode before sweeping. At this point, it
-** does not know the real memory in use, so it cannot use memory to
-** decide whether to return to generational mode. Instead, it uses the
-** number of objects traversed (returned by 'atomic') as a proxy. The
-** field 'g->lastatomic' keeps this count from the last collection.
-** ('g->lastatomic != 0' also means that the last collection was bad.)
-*/
-static void stepgenfull (lua_State *L, global_State *g) {
-  lu_mem newatomic;  /* count of traversed objects */
-  lu_mem lastatomic = g->lastatomic;  /* count from last collection */
-  if (g->gckind == KGC_GEN)  /* still in generational mode? */
-    enterinc(g);  /* enter incremental mode */
+  entergen(L, g);
+}
+
+
+/*
+** Does a major collector up to the atomic phase and then either
+** returns to minor collections or stays doing major ones.  If the
+** number of objects collected this time (numobjs - marked) is more than
+** half the number of objects created since the last major collection
+** (numobjs - lastmajor), it goes back to minor collections.
+*/
+static void genmajorstep (lua_State *L, global_State *g) {
+  l_obj lastmajor = g->GClastmajor;  /* count from last collection */
+  l_obj numobjs = gettotalobjs(g);  /* current count */
   luaC_runtilstate(L, bitmask(GCSpropagate));  /* start new cycle */
-  newatomic = atomic(L);  /* mark everybody */
-  if (newatomic < lastatomic + (lastatomic >> 3)) {  /* good collection? */
+  atomic(L);  /* mark everybody */
+  if ((numobjs - g->marked) > ((numobjs - lastmajor) >> 1)) {
     atomic2gen(L, g);  /* return to generational mode */
     setminordebt(g);
   }
-  else {  /* another bad collection; stay in incremental mode */
-    g->GCestimate = gettotalbytes(g);  /* first estimate */
+  else {  /* bad collection; stay in major mode */
     entersweep(L);
     luaC_runtilstate(L, bitmask(GCSpause));  /* finish collection */
     setpause(g);
-    g->lastatomic = newatomic;
+    g->GClastmajor = gettotalobjs(g);
   }
 }
 
 
 /*
-** Does a generational "step".
-** Usually, this means doing a minor collection and setting the debt to
-** make another collection when memory grows 'genminormul'% larger.
-**
-** However, there are exceptions.  If memory grows 'genmajormul'%
-** larger than it was at the end of the last major collection (kept
-** in 'g->GCestimate'), the function does a major collection. At the
-** end, it checks whether the major collection was able to free a
-** decent amount of memory (at least half the growth in memory since
-** previous major collection). If so, the collector keeps its state,
-** and the next collection will probably be minor again. Otherwise,
-** we have what we call a "bad collection". In that case, set the field
-** 'g->lastatomic' to signal that fact, so that the next collection will
-** go to 'stepgenfull'.
-**
-** 'GCdebt <= 0' means an explicit call to GC step with "size" zero;
-** in that case, do a minor collection.
+** Does a generational "step".  If the total number of objects grew
+** more than 'majormul'% since the last major collection, does a
+** major collection.  Otherwise, does a minor collection.
 */
 static void genstep (lua_State *L, global_State *g) {
-  if (g->lastatomic != 0)  /* last collection was a bad one? */
-    stepgenfull(L, g);  /* do a full step */
-  else {
-    lu_mem majorbase = g->GCestimate;  /* memory after last major collection */
-    lu_mem majorinc = (majorbase / 100) * getgcparam(g->genmajormul);
-    if (g->GCdebt > 0 && gettotalbytes(g) > majorbase + majorinc) {
-      lu_mem numobjs = fullgen(L, g);  /* do a major collection */
-      if (gettotalbytes(g) < majorbase + (majorinc / 2)) {
-        /* collected at least half of memory growth since last major
-           collection; keep doing minor collections. */
-        lua_assert(g->lastatomic == 0);
-      }
-      else {  /* bad collection */
-        g->lastatomic = numobjs;  /* signal that last collection was bad */
-        setpause(g);  /* do a long wait for next (major) collection */
-      }
-    }
-    else {  /* regular case; do a minor collection */
-      youngcollection(L, g);
-      setminordebt(g);
-      g->GCestimate = majorbase;  /* preserve base value */
-    }
+  l_obj majorbase = g->GClastmajor;  /* count after last major collection */
+  l_obj majorinc = applygcparam(g, genmajormul, majorbase);
+  if (gettotalobjs(g) > majorbase + majorinc && 0) {
+    /* do a major collection */
+    enterinc(g);
+    g->gckind = KGC_GENMAJOR;
+    genmajorstep(L, g);
+  }
+  else {  /* regular case; do a minor collection */
+    g->marked = 0;
+    youngcollection(L, g);
+    setminordebt(g);
+    lua_assert(g->GClastmajor == majorbase);
   }
-  lua_assert(isdecGCmodegen(g));
 }
 
 /* }====================================================== */
@@ -1520,9 +1451,9 @@ void luaC_freeallobjects (lua_State *L) {
 }
 
 
-static lu_mem atomic (lua_State *L) {
+static l_obj atomic (lua_State *L) {
+  l_obj work = 0;
   global_State *g = G(L);
-  lu_mem work = 0;
   GCObject *origweak, *origall;
   GCObject *grayagain = g->grayagain;  /* save original list */
   g->grayagain = NULL;
@@ -1539,50 +1470,44 @@ static lu_mem atomic (lua_State *L) {
   work += propagateall(g);  /* propagate changes */
   g->gray = grayagain;
   work += propagateall(g);  /* traverse 'grayagain' list */
-  convergeephemerons(g);
+  work += convergeephemerons(g);
   /* at this point, all strongly accessible objects are marked. */
   /* Clear values from weak tables, before checking finalizers */
-  clearbyvalues(g, g->weak, NULL);
-  clearbyvalues(g, g->allweak, NULL);
+  work += clearbyvalues(g, g->weak, NULL);
+  work += clearbyvalues(g, g->allweak, NULL);
   origweak = g->weak; origall = g->allweak;
   separatetobefnz(g, 0);  /* separate objects to be finalized */
   work += markbeingfnz(g);  /* mark objects that will be finalized */
   work += propagateall(g);  /* remark, to propagate 'resurrection' */
-  convergeephemerons(g);
+  work += convergeephemerons(g);
   /* at this point, all resurrected objects are marked. */
   /* remove dead objects from weak tables */
-  clearbykeys(g, g->ephemeron);  /* clear keys from all ephemeron tables */
-  clearbykeys(g, g->allweak);  /* clear keys from all 'allweak' tables */
+  work += clearbykeys(g, g->ephemeron);  /* clear keys from all ephemeron */
+  work += clearbykeys(g, g->allweak);  /* clear keys from all 'allweak' */
   /* clear values from resurrected weak tables */
-  clearbyvalues(g, g->weak, origweak);
-  clearbyvalues(g, g->allweak, origall);
+  work += clearbyvalues(g, g->weak, origweak);
+  work += clearbyvalues(g, g->allweak, origall);
   luaS_clearcache(g);
   g->currentwhite = cast_byte(otherwhite(g));  /* flip current white */
   lua_assert(g->gray == NULL);
-  return work;  /* estimate of slots marked by 'atomic' */
+  return work;
 }
 
 
-static int sweepstep (lua_State *L, global_State *g,
-                      int nextstate, GCObject **nextlist) {
-  if (g->sweepgc) {
-    l_mem olddebt = g->GCdebt;
-    int count;
-    g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX, &count);
-    g->GCestimate += g->GCdebt - olddebt;  /* update estimate */
-    return count;
-  }
+static void sweepstep (lua_State *L, global_State *g,
+                       int nextstate, GCObject **nextlist) {
+  if (g->sweepgc)
+    g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX);
   else {  /* enter next state */
     g->gcstate = nextstate;
     g->sweepgc = nextlist;
-    return 0;  /* no work done */
   }
 }
 
 
-static lu_mem singlestep (lua_State *L) {
+static l_obj singlestep (lua_State *L) {
   global_State *g = G(L);
-  lu_mem work;
+  l_obj work;
   lua_assert(!g->gcstopem);  /* collector is not reentrant */
   g->gcstopem = 1;  /* no emergency collections while collecting */
   switch (g->gcstate) {
@@ -1597,26 +1522,30 @@ static lu_mem singlestep (lua_State *L) {
         g->gcstate = GCSenteratomic;  /* finish propagate phase */
         work = 0;
       }
-      else
-        work = propagatemark(g);  /* traverse one gray object */
+      else {
+        propagatemark(g);  /* traverse one gray object */
+        work = 1;
+      }
       break;
     }
     case GCSenteratomic: {
-      work = atomic(L);  /* work is what was traversed by 'atomic' */
+      work = atomic(L);
       entersweep(L);
-      g->GCestimate = gettotalbytes(g);  /* first estimate */
       break;
     }
     case GCSswpallgc: {  /* sweep "regular" objects */
-      work = sweepstep(L, g, GCSswpfinobj, &g->finobj);
+      sweepstep(L, g, GCSswpfinobj, &g->finobj);
+      work = GCSWEEPMAX;
       break;
     }
     case GCSswpfinobj: {  /* sweep objects with finalizers */
-      work = sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
+      sweepstep(L, g, GCSswptobefnz, &g->tobefnz);
+      work = GCSWEEPMAX;
       break;
     }
     case GCSswptobefnz: {  /* sweep objects to be finalized */
-      work = sweepstep(L, g, GCSswpend, NULL);
+      sweepstep(L, g, GCSswpend, NULL);
+      work = GCSWEEPMAX;
       break;
     }
     case GCSswpend: {  /* finish sweeps */
@@ -1625,10 +1554,11 @@ static lu_mem singlestep (lua_State *L) {
       work = 0;
       break;
     }
-    case GCScallfin: {  /* call remaining finalizers */
+    case GCScallfin: {  /* call finalizers */
       if (g->tobefnz && !g->gcemergency) {
         g->gcstopem = 0;  /* ok collections during finalizers */
-        work = runafewfinalizers(L, GCFINMAX) * GCFINALIZECOST;
+        GCTM(L);  /* call one finalizer */
+        work = 1;
       }
       else {  /* emergency mode or no more finalizers */
         g->gcstate = GCSpause;  /* finish collection */
@@ -1663,20 +1593,16 @@ void luaC_runtilstate (lua_State *L, int statesmask) {
 ** controls when next step will be performed.
 */
 static void incstep (lua_State *L, global_State *g) {
-  int stepmul = (getgcparam(g->gcstepmul) | 1);  /* avoid division by 0 */
-  l_mem debt = (g->GCdebt / WORK2MEM) * stepmul;
-  l_mem stepsize = (g->gcstepsize <= log2maxs(l_mem))
-                 ? ((cast(l_mem, 1) << g->gcstepsize) / WORK2MEM) * stepmul
-                 : MAX_LMEM;  /* overflow; keep maximum value */
+  l_obj stepsize = cast(l_obj, 1) << g->gcstepsize;
+  l_obj work2do = applygcparam(g, gcstepmul, stepsize);
   do {  /* repeat until pause or enough "credit" (negative debt) */
-    lu_mem work = singlestep(L);  /* perform one single step */
-    debt -= work;
-  } while (debt > -stepsize && g->gcstate != GCSpause);
+    l_obj work = singlestep(L);  /* perform one single step */
+    work2do -= work;
+  } while (work2do > 0 && g->gcstate != GCSpause);
   if (g->gcstate == GCSpause)
     setpause(g);  /* pause until next cycle */
   else {
-    debt = (debt / stepmul) * WORK2MEM;  /* convert 'work units' to bytes */
-    luaE_setdebt(g, debt);
+    luaE_setdebt(g, stepsize);
   }
 }
 
@@ -1687,13 +1613,21 @@ static void incstep (lua_State *L, global_State *g) {
 */
 void luaC_step (lua_State *L) {
   global_State *g = G(L);
+  lua_assert(!g->gcemergency);
   if (!gcrunning(g))  /* not running? */
-    luaE_setdebt(g, -2000);
+    luaE_setdebt(g, 2000);
   else {
-    if(isdecGCmodegen(g))
-      genstep(L, g);
-    else
-      incstep(L, g);
+    switch (g->gckind) {
+      case KGC_INC:
+        incstep(L, g);
+        break;
+      case KGC_GEN:
+        genstep(L, g);
+        break;
+      case KGC_GENMAJOR:
+        genmajorstep(L, g);
+        break;
+    }
   }
 }
 
@@ -1711,8 +1645,8 @@ static void fullinc (lua_State *L, global_State *g) {
   /* finish any pending sweep phase to start a new cycle */
   luaC_runtilstate(L, bitmask(GCSpause));
   luaC_runtilstate(L, bitmask(GCScallfin));  /* run up to finalizers */
-  /* estimate must be correct after a full GC cycle */
-  lua_assert(g->GCestimate == gettotalbytes(g));
+  /* 'marked' must be correct after a full GC cycle */
+  lua_assert(g->marked == gettotalobjs(g));
   luaC_runtilstate(L, bitmask(GCSpause));  /* finish collection */
   setpause(g);
 }
@@ -1727,10 +1661,10 @@ void luaC_fullgc (lua_State *L, int isemergency) {
   global_State *g = G(L);
   lua_assert(!g->gcemergency);
   g->gcemergency = isemergency;  /* set flag */
-  if (g->gckind == KGC_INC)
-    fullinc(L, g);
-  else
+  if (g->gckind == KGC_GEN)
     fullgen(L, g);
+  else
+    fullinc(L, g);
   g->gcemergency = 0;
 }
 
diff --git a/lgc.h b/lgc.h
index 538f6edc..959465ec 100644
--- a/lgc.h
+++ b/lgc.h
@@ -8,6 +8,9 @@
 #define lgc_h
 
 
+#include <stddef.h>
+
+
 #include "lobject.h"
 #include "lstate.h"
 
@@ -122,31 +125,21 @@
 
 
 /* Default Values for GC parameters */
-#define LUAI_GENMAJORMUL         100
-#define LUAI_GENMINORMUL         20
 
-/* wait memory to double before starting new cycle */
-#define LUAI_GCPAUSE    200
+/* generational */
 
-/*
-** some gc parameters are stored divided by 4 to allow a maximum value
-** up to 1023 in a 'lu_byte'.
-*/
-#define getgcparam(p)   ((p) * 4)
-#define setgcparam(p,v) ((p) = (v) / 4)
+#define LUAI_GENMAJORMUL         100    /* major multiplier */
+#define LUAI_GENMINORMUL         20     /* minor multiplier */
 
-#define LUAI_GCMUL      100
+/* incremental */
 
-/* how much to allocate before next GC step (log2) */
-#define LUAI_GCSTEPSIZE 13      /* 8 KB */
+/* wait memory to double before starting new cycle */
+#define LUAI_GCPAUSE    200
 
+#define LUAI_GCMUL      300     /* step multiplier */
 
-/*
-** Check whether the declared GC mode is generational. While in
-** generational mode, the collector can go temporarily to incremental
-** mode to improve performance. This is signaled by 'g->lastatomic != 0'.
-*/
-#define isdecGCmodegen(g)       (g->gckind == KGC_GEN || g->lastatomic != 0)
+/* how many objects to allocate before next GC step (log2) */
+#define LUAI_GCSTEPSIZE 8      /* 256 objects */
 
 
 /*
@@ -157,15 +150,38 @@
 #define GCSTPCLS        4  /* bit true when closing Lua state */
 #define gcrunning(g)    ((g)->gcstp == 0)
 
+/*
+** Macros to set and apply GC parameters. GC parameters are given in
+** percentage points, but are stored as lu_byte. To reduce their
+** values and avoid repeated divisions by 100, these macros store
+** the original parameter multiplied by 2^n and divided by 100.
+** To apply them, the value is divided by 2^n (a shift) and then
+** multiplied by the stored parameter, yielding
+** value / 2^n * (original parameter * 2^n / 100), or approximately
+** (value * original parameter / 100).
+**
+** For most parameters, which are typically larger than 100%, 2^n is
+** 16 (2^4), allowing maximum values up to 1599.  For the minor
+** multiplier, which is typically smaller, 2^n is 64 (2^6) to allow more
+** precision.
+*/
+#define gcparamshift(p)  \
+  (offsetof(global_State, p) == offsetof(global_State, genminormul) ? 6 : 4)
+
+#define setgcparam(g,p,v)  \
+        (g->p = (cast_uint(v) << gcparamshift(p)) / 100u)
+#define applygcparam(g,p,v)     (((v) >> gcparamshift(p)) * g->p)
+
+
 
 /*
-** Does one step of collection when debt becomes positive. 'pre'/'pos'
+** Does one step of collection when debt becomes zero. 'pre'/'pos'
 ** allows some adjustments to be done only when needed. macro
 ** 'condchangemem' is used only for heavy tests (forcing a full
 ** GC cycle on every opportunity)
 */
 #define luaC_condGC(L,pre,pos) \
-        { if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
+        { if (G(L)->GCdebt <= 0) { pre; luaC_step(L); pos;}; \
           condchangemem(L,pre,pos); }
 
 /* more often than not, 'pre'/'pos' are empty */
diff --git a/linit.c b/linit.c
index 69808f84..675fb65f 100644
--- a/linit.c
+++ b/linit.c
@@ -8,21 +8,6 @@
 #define linit_c
 #define LUA_LIB
 
-/*
-** If you embed Lua in your program and need to open the standard
-** libraries, call luaL_openlibs in your program. If you need a
-** different set of libraries, copy this file to your project and edit
-** it to suit your needs.
-**
-** You can also *preload* libraries, so that a later 'require' can
-** open the library, which is already linked to the application.
-** For that, do the following code:
-**
-**  luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);
-**  lua_pushcfunction(L, luaopen_modname);
-**  lua_setfield(L, -2, modname);
-**  lua_pop(L, 1);  // remove PRELOAD table
-*/
 
 #include "lprefix.h"
 
@@ -36,30 +21,44 @@
 
 
 /*
-** these libs are loaded by lua.c and are readily available to any Lua
-** program
+** Standard Libraries
 */
-static const luaL_Reg loadedlibs[] = {
+static const luaL_Reg stdlibs[] = {
   {LUA_GNAME, luaopen_base},
   {LUA_LOADLIBNAME, luaopen_package},
+
   {LUA_COLIBNAME, luaopen_coroutine},
-  {LUA_TABLIBNAME, luaopen_table},
+  {LUA_DBLIBNAME, luaopen_debug},
   {LUA_IOLIBNAME, luaopen_io},
+  {LUA_MATHLIBNAME, luaopen_math},
   {LUA_OSLIBNAME, luaopen_os},
   {LUA_STRLIBNAME, luaopen_string},
-  {LUA_MATHLIBNAME, luaopen_math},
+  {LUA_TABLIBNAME, luaopen_table},
   {LUA_UTF8LIBNAME, luaopen_utf8},
-  {LUA_DBLIBNAME, luaopen_debug},
+
   {NULL, NULL}
 };
 
 
-LUALIB_API void luaL_openlibs (lua_State *L) {
+/*
+** require selected standard libraries and add the others to the
+** preload table.
+*/
+LUALIB_API void luaL_openselectedlibs (lua_State *L, int what) {
+  int mask = 1;
   const luaL_Reg *lib;
-  /* "require" functions from 'loadedlibs' and set results to global table */
-  for (lib = loadedlibs; lib->func; lib++) {
-    luaL_requiref(L, lib->name, lib->func, 1);
-    lua_pop(L, 1);  /* remove lib */
+  luaL_getsubtable(L, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);
+  for (lib = stdlibs; lib->func; (lib++, mask <<= 1)) {
+    if (what & mask) {  /* selected? */
+      luaL_requiref(L, lib->name, lib->func, 1);  /* require library */
+      lua_pop(L, 1);  /* remove result from the stack */
+    }
+    else {  /* add library to PRELOAD table */
+      lua_pushcfunction(L, lib->func);
+      lua_setfield(L, -2, lib->name);
+    }
   }
+  lua_assert((mask >> 1) == LUA_UTF8LIBK);
+  lua_pop(L, 1);  // remove PRELOAD table
 }
 
diff --git a/llimits.h b/llimits.h
index 1c826f7b..47dee9a6 100644
--- a/llimits.h
+++ b/llimits.h
@@ -16,21 +16,25 @@
 
 
 /*
-** 'lu_mem' and 'l_mem' are unsigned/signed integers big enough to count
-** the total memory used by Lua (in bytes). Usually, 'size_t' and
+** 'lu_mem' is an unsigned integer big enough to count the total memory
+** used by Lua (in bytes). 'l_obj' is a signed integer big enough to
+** count the total number of objects used by Lua. (It is signed due
+** to the use of debt in several computations.)  Usually, 'size_t' and
 ** 'ptrdiff_t' should work, but we use 'long' for 16-bit machines.
 */
 #if defined(LUAI_MEM)           /* { external definitions? */
 typedef LUAI_UMEM lu_mem;
-typedef LUAI_MEM l_mem;
+typedef LUAI_MEM l_obj;
 #elif LUAI_IS32INT      /* }{ */
 typedef size_t lu_mem;
-typedef ptrdiff_t l_mem;
+typedef ptrdiff_t l_obj;
 #else  /* 16-bit ints */        /* }{ */
 typedef unsigned long lu_mem;
-typedef long l_mem;
+typedef long l_obj;
 #endif                          /* } */
 
+#define MAX_LOBJ        cast(l_obj, ~cast(lu_mem, 0) >> 1)
+
 
 /* chars used as small naturals (so that 'char' is reserved for characters) */
 typedef unsigned char lu_byte;
@@ -45,11 +49,6 @@ typedef signed char ls_byte;
                           : (size_t)(LUA_MAXINTEGER))
 
 
-#define MAX_LUMEM       ((lu_mem)(~(lu_mem)0))
-
-#define MAX_LMEM        ((l_mem)(MAX_LUMEM >> 1))
-
-
 #define MAX_INT         INT_MAX  /* maximum value of an int */
 
 
@@ -57,7 +56,7 @@ typedef signed char ls_byte;
 ** floor of the log2 of the maximum signed value for integral type 't'.
 ** (That is, maximum 'n' such that '2^n' fits in the given signed type.)
 */
-#define log2maxs(t)     (sizeof(t) * 8 - 2)
+#define log2maxs(t)     cast_int(sizeof(t) * 8 - 2)
 
 
 /*
diff --git a/lmathlib.c b/lmathlib.c
index d0b1e1e5..6d63950c 100644
--- a/lmathlib.c
+++ b/lmathlib.c
@@ -603,28 +603,18 @@ static void setseed (lua_State *L, Rand64 *state,
 }
 
 
-/*
-** Set a "random" seed. To get some randomness, use the current time
-** and the address of 'L' (in case the machine does address space layout
-** randomization).
-*/
-static void randseed (lua_State *L, RanState *state) {
-  lua_Unsigned seed1 = (lua_Unsigned)time(NULL);
-  lua_Unsigned seed2 = (lua_Unsigned)(size_t)L;
-  setseed(L, state->s, seed1, seed2);
-}
-
-
 static int math_randomseed (lua_State *L) {
   RanState *state = (RanState *)lua_touserdata(L, lua_upvalueindex(1));
+  lua_Unsigned n1, n2;
   if (lua_isnone(L, 1)) {
-    randseed(L, state);
+    n1 = luaL_makeseed(L);  /* "random" seed */
+    n2 = I2UInt(nextrand(state->s));  /* in case seed is not that random... */
   }
   else {
-    lua_Integer n1 = luaL_checkinteger(L, 1);
-    lua_Integer n2 = luaL_optinteger(L, 2, 0);
-    setseed(L, state->s, n1, n2);
+    n1 = luaL_checkinteger(L, 1);
+    n2 = luaL_optinteger(L, 2, 0);
   }
+  setseed(L, state->s, n1, n2);
   return 2;  /* return seeds */
 }
 
@@ -641,7 +631,7 @@ static const luaL_Reg randfuncs[] = {
 */
 static void setrandfunc (lua_State *L) {
   RanState *state = (RanState *)lua_newuserdatauv(L, sizeof(RanState), 0);
-  randseed(L, state);  /* initialize with a "random" seed */
+  setseed(L, state->s, luaL_makeseed(L), 0);  /* initialize with random seed */
   lua_pop(L, 2);  /* remove pushed seeds */
   luaL_setfuncs(L, randfuncs, 1);
 }
diff --git a/lmem.c b/lmem.c
index 9800a86f..dfd8a49b 100644
--- a/lmem.c
+++ b/lmem.c
@@ -151,7 +151,7 @@ void luaM_free_ (lua_State *L, void *block, size_t osize) {
   global_State *g = G(L);
   lua_assert((osize == 0) == (block == NULL));
   callfrealloc(g, block, osize, 0);
-  g->GCdebt -= osize;
+  g->totalbytes -= osize;
 }
 
 
@@ -181,10 +181,10 @@ void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
   if (l_unlikely(newblock == NULL && nsize > 0)) {
     newblock = tryagain(L, block, osize, nsize);
     if (newblock == NULL)  /* still no memory? */
-      return NULL;  /* do not update 'GCdebt' */
+      return NULL;  /* do not update 'totalbytes' */
   }
   lua_assert((nsize == 0) == (newblock == NULL));
-  g->GCdebt = (g->GCdebt + nsize) - osize;
+  g->totalbytes += nsize - osize;
   return newblock;
 }
 
@@ -209,7 +209,7 @@ void *luaM_malloc_ (lua_State *L, size_t size, int tag) {
       if (newblock == NULL)
         luaM_error(L);
     }
-    g->GCdebt += size;
+    g->totalbytes += size;
     return newblock;
   }
 }
diff --git a/lmem.h b/lmem.h
index 8c75a44b..c5dada9c 100644
--- a/lmem.h
+++ b/lmem.h
@@ -63,6 +63,8 @@
 
 #define luaM_newobject(L,tag,s) luaM_malloc_(L, (s), tag)
 
+#define luaM_newblock(L, size)  luaM_newvector(L, size, char)
+
 #define luaM_growvector(L,v,nelems,size,t,limit,e) \
         ((v)=cast(t *, luaM_growaux_(L,v,nelems,&(size),sizeof(t), \
                          luaM_limitN(limit,t),e)))
diff --git a/lobject.h b/lobject.h
index 556608e4..1c300e86 100644
--- a/lobject.h
+++ b/lobject.h
@@ -743,7 +743,6 @@ typedef struct Table {
   unsigned int alimit;  /* "limit" of 'array' array */
   TValue *array;  /* array part */
   Node *node;
-  Node *lastfree;  /* any free position is before this position */
   struct Table *metatable;
   GCObject *gclist;
 } Table;
diff --git a/lparser.c b/lparser.c
index b745f236..2ac04160 100644
--- a/lparser.c
+++ b/lparser.c
@@ -187,10 +187,10 @@ static int registerlocalvar (LexState *ls, FuncState *fs, TString *varname) {
 
 
 /*
-** Create a new local variable with the given 'name'. Return its index
-** in the function.
+** Create a new local variable with the given 'name' and given 'kind'.
+** Return its index in the function.
 */
-static int new_localvar (LexState *ls, TString *name) {
+static int new_localvarkind (LexState *ls, TString *name, int kind) {
   lua_State *L = ls->L;
   FuncState *fs = ls->fs;
   Dyndata *dyd = ls->dyd;
@@ -200,11 +200,19 @@ static int new_localvar (LexState *ls, TString *name) {
   luaM_growvector(L, dyd->actvar.arr, dyd->actvar.n + 1,
                   dyd->actvar.size, Vardesc, USHRT_MAX, "local variables");
   var = &dyd->actvar.arr[dyd->actvar.n++];
-  var->vd.kind = VDKREG;  /* default */
+  var->vd.kind = kind;  /* default */
   var->vd.name = name;
   return dyd->actvar.n - 1 - fs->firstlocal;
 }
 
+
+/*
+** Create a new local variable with the given 'name' and regular kind.
+*/
+static int new_localvar (LexState *ls, TString *name) {
+  return new_localvarkind(ls, name, VDKREG);
+}
+
 #define new_localvarliteral(ls,v) \
     new_localvar(ls,  \
       luaX_newstring(ls, "" v, (sizeof(v)/sizeof(char)) - 1));
@@ -1550,6 +1558,7 @@ static void forbody (LexState *ls, int base, int line, int nvars, int isgen) {
   int prep, endfor;
   checknext(ls, TK_DO);
   prep = luaK_codeABx(fs, forprep[isgen], base, 0);
+  fs->freereg--;  /* both 'forprep' remove one register from the stack */
   enterblock(fs, &bl, 0);  /* scope for declared variables */
   adjustlocalvars(ls, nvars);
   luaK_reserveregs(fs, nvars);
@@ -1572,8 +1581,7 @@ static void fornum (LexState *ls, TString *varname, int line) {
   int base = fs->freereg;
   new_localvarliteral(ls, "(for state)");
   new_localvarliteral(ls, "(for state)");
-  new_localvarliteral(ls, "(for state)");
-  new_localvar(ls, varname);
+  new_localvarkind(ls, varname, RDKCONST);  /* control variable */
   checknext(ls, '=');
   exp1(ls);  /* initial value */
   checknext(ls, ',');
@@ -1584,7 +1592,7 @@ static void fornum (LexState *ls, TString *varname, int line) {
     luaK_int(fs, fs->freereg, 1);
     luaK_reserveregs(fs, 1);
   }
-  adjustlocalvars(ls, 3);  /* control variables */
+  adjustlocalvars(ls, 2);  /* start scope for internal variables */
   forbody(ls, base, line, 1, 0);
 }
 
@@ -1593,16 +1601,15 @@ static void forlist (LexState *ls, TString *indexname) {
   /* forlist -> NAME {,NAME} IN explist forbody */
   FuncState *fs = ls->fs;
   expdesc e;
-  int nvars = 5;  /* gen, state, control, toclose, 'indexname' */
+  int nvars = 4;  /* function, state, closing, control */
   int line;
   int base = fs->freereg;
-  /* create control variables */
-  new_localvarliteral(ls, "(for state)");
-  new_localvarliteral(ls, "(for state)");
-  new_localvarliteral(ls, "(for state)");
-  new_localvarliteral(ls, "(for state)");
-  /* create declared variables */
-  new_localvar(ls, indexname);
+  /* create internal variables */
+  new_localvarliteral(ls, "(for state)");  /* iterator function */
+  new_localvarliteral(ls, "(for state)");  /* state */
+  new_localvarliteral(ls, "(for state)");  /* closing var. (after swap) */
+  new_localvarkind(ls, indexname, RDKCONST);  /* control variable */
+  /* other declared variables */
   while (testnext(ls, ',')) {
     new_localvar(ls, str_checkname(ls));
     nvars++;
@@ -1610,10 +1617,10 @@ static void forlist (LexState *ls, TString *indexname) {
   checknext(ls, TK_IN);
   line = ls->linenumber;
   adjust_assign(ls, 4, explist(ls, &e), &e);
-  adjustlocalvars(ls, 4);  /* control variables */
-  marktobeclosed(fs);  /* last control var. must be closed */
-  luaK_checkstack(fs, 3);  /* extra space to call generator */
-  forbody(ls, base, line, nvars - 4, 1);
+  adjustlocalvars(ls, 3);  /* start scope for internal variables */
+  marktobeclosed(fs);  /* last internal var. must be closed */
+  luaK_checkstack(fs, 2);  /* extra space to call iterator */
+  forbody(ls, base, line, nvars - 3, 1);
 }
 
 
@@ -1728,14 +1735,14 @@ static void localstat (LexState *ls) {
   FuncState *fs = ls->fs;
   int toclose = -1;  /* index of to-be-closed variable (if any) */
   Vardesc *var;  /* last variable */
-  int vidx, kind;  /* index and kind of last variable */
+  int vidx;  /* index of last variable */
   int nvars = 0;
   int nexps;
   expdesc e;
   do {
-    vidx = new_localvar(ls, str_checkname(ls));
-    kind = getlocalattribute(ls);
-    getlocalvardesc(fs, vidx)->vd.kind = kind;
+    TString *vname = str_checkname(ls);
+    int kind = getlocalattribute(ls);
+    vidx = new_localvarkind(ls, vname, kind);
     if (kind == RDKTOCLOSE) {  /* to-be-closed? */
       if (toclose != -1)  /* one already present? */
         luaK_semerror(ls, "multiple to-be-closed variables in local list");
diff --git a/lstate.c b/lstate.c
index 06667dac..37301c3c 100644
--- a/lstate.c
+++ b/lstate.c
@@ -52,46 +52,15 @@ typedef struct LG {
 
 
 /*
-** A macro to create a "random" seed when a state is created;
-** the seed is used to randomize string hashes.
+** set GCdebt to a new value keeping the value (totalobjs + GCdebt)
+** invariant (and avoiding underflows in 'totalobjs')
 */
-#if !defined(luai_makeseed)
-
-#include <time.h>
-
-/*
-** Compute an initial seed with some level of randomness.
-** Rely on Address Space Layout Randomization (if present) and
-** current time.
-*/
-#define addbuff(b,p,e) \
-  { size_t t = cast_sizet(e); \
-    memcpy(b + p, &t, sizeof(t)); p += sizeof(t); }
-
-static unsigned int luai_makeseed (lua_State *L) {
-  char buff[3 * sizeof(size_t)];
-  unsigned int h = cast_uint(time(NULL));
-  int p = 0;
-  addbuff(buff, p, L);  /* heap variable */
-  addbuff(buff, p, &h);  /* local variable */
-  addbuff(buff, p, &lua_newstate);  /* public function */
-  lua_assert(p == sizeof(buff));
-  return luaS_hash(buff, p, h);
-}
-
-#endif
-
-
-/*
-** set GCdebt to a new value keeping the value (totalbytes + GCdebt)
-** invariant (and avoiding underflows in 'totalbytes')
-*/
-void luaE_setdebt (global_State *g, l_mem debt) {
-  l_mem tb = gettotalbytes(g);
+void luaE_setdebt (global_State *g, l_obj debt) {
+  l_obj tb = gettotalobjs(g);
   lua_assert(tb > 0);
-  if (debt < tb - MAX_LMEM)
-    debt = tb - MAX_LMEM;  /* will make 'totalbytes == MAX_LMEM' */
-  g->totalbytes = tb - debt;
+  if (debt > MAX_LOBJ - tb)
+    debt = MAX_LOBJ - tb;  /* will make 'totalobjs == MAX_LMEM' */
+  g->totalobjs = tb + debt;
   g->GCdebt = debt;
 }
 
@@ -278,7 +247,8 @@ static void close_state (lua_State *L) {
   }
   luaM_freearray(L, G(L)->strt.hash, G(L)->strt.size);
   freestack(L);
-  lua_assert(gettotalbytes(g) == sizeof(LG));
+  lua_assert(g->totalbytes == sizeof(LG));
+  lua_assert(gettotalobjs(g) == 1);
   (*g->frealloc)(g->ud, fromstate(L), sizeof(LG), 0);  /* free main block */
 }
 
@@ -349,15 +319,7 @@ LUA_API int lua_closethread (lua_State *L, lua_State *from) {
 }
 
 
-/*
-** Deprecated! Use 'lua_closethread' instead.
-*/
-LUA_API int lua_resetthread (lua_State *L) {
-  return lua_closethread(L, NULL);
-}
-
-
-LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
+LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud, unsigned int seed) {
   int i;
   lua_State *L;
   global_State *g;
@@ -377,7 +339,7 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->warnf = NULL;
   g->ud_warn = NULL;
   g->mainthread = L;
-  g->seed = luai_makeseed(L);
+  g->seed = seed;
   g->gcstp = GCSTPGC;  /* no GC while building state */
   g->strt.size = g->strt.nuse = 0;
   g->strt.hash = NULL;
@@ -395,14 +357,15 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->weak = g->ephemeron = g->allweak = NULL;
   g->twups = NULL;
   g->totalbytes = sizeof(LG);
+  g->totalobjs = 1;
+  g->marked = 0;
   g->GCdebt = 0;
-  g->lastatomic = 0;
   setivalue(&g->nilvalue, 0);  /* to signal that state is not yet built */
-  setgcparam(g->gcpause, LUAI_GCPAUSE);
-  setgcparam(g->gcstepmul, LUAI_GCMUL);
+  setgcparam(g, gcpause, LUAI_GCPAUSE);
+  setgcparam(g, gcstepmul, LUAI_GCMUL);
   g->gcstepsize = LUAI_GCSTEPSIZE;
-  setgcparam(g->genmajormul, LUAI_GENMAJORMUL);
-  g->genminormul = LUAI_GENMINORMUL;
+  setgcparam(g, genmajormul, LUAI_GENMAJORMUL);
+  setgcparam(g, genminormul, LUAI_GENMINORMUL);
   for (i=0; i < LUA_NUMTAGS; i++) g->mt[i] = NULL;
   if (luaD_rawrunprotected(L, f_luaopen, NULL) != LUA_OK) {
     /* memory allocation error: free partial state */
diff --git a/lstate.h b/lstate.h
index 40ff89aa..488d2c5a 100644
--- a/lstate.h
+++ b/lstate.h
@@ -150,12 +150,13 @@ struct lua_longjmp;  /* defined in ldo.c */
 /* kinds of Garbage Collection */
 #define KGC_INC         0       /* incremental gc */
 #define KGC_GEN         1       /* generational gc */
+#define KGC_GENMAJOR    2       /* generational in "major" mode */
 
 
 typedef struct stringtable {
-  TString **hash;
+  TString **hash;  /* array of buckets (linked lists of strings) */
   int nuse;  /* number of elements */
-  int size;
+  int size;  /* number of buckets */
 } stringtable;
 
 
@@ -254,10 +255,11 @@ struct CallInfo {
 typedef struct global_State {
   lua_Alloc frealloc;  /* function to reallocate memory */
   void *ud;         /* auxiliary data to 'frealloc' */
-  l_mem totalbytes;  /* number of bytes currently allocated - GCdebt */
-  l_mem GCdebt;  /* bytes allocated not yet compensated by the collector */
-  lu_mem GCestimate;  /* an estimate of the non-garbage memory in use */
-  lu_mem lastatomic;  /* see function 'genstep' in file 'lgc.c' */
+  lu_mem totalbytes;  /* number of bytes currently allocated */
+  l_obj totalobjs;  /* total number of objects allocated + GCdebt */
+  l_obj GCdebt;  /* objects counted but not yet allocated */
+  l_obj marked;  /* number of objects marked in a GC cycle */
+  l_obj GClastmajor;  /* objects at last major collection */
   stringtable strt;  /* hash table for strings */
   TValue l_registry;
   TValue nilvalue;  /* a nil value */
@@ -390,10 +392,11 @@ union GCUnion {
 #define obj2gco(v)      check_exp((v)->tt >= LUA_TSTRING, &(cast_u(v)->gc))
 
 
-/* actual number of total bytes allocated */
-#define gettotalbytes(g)        cast(lu_mem, (g)->totalbytes + (g)->GCdebt)
+/* actual number of total objects allocated */
+#define gettotalobjs(g) ((g)->totalobjs - (g)->GCdebt)
 
-LUAI_FUNC void luaE_setdebt (global_State *g, l_mem debt);
+
+LUAI_FUNC void luaE_setdebt (global_State *g, l_obj debt);
 LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
 LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
 LUAI_FUNC void luaE_shrinkCI (lua_State *L);
diff --git a/lstrlib.c b/lstrlib.c
index 03167161..e29c09b9 100644
--- a/lstrlib.c
+++ b/lstrlib.c
@@ -239,6 +239,7 @@ static int str_dump (lua_State *L) {
   if (l_unlikely(lua_dump(L, writer, &state, strip) != 0))
     return luaL_error(L, "unable to dump given function");
   luaL_pushresult(&state.B);
+  lua_assert(lua_isfunction(L, 1));  /* lua_dump kept that value */
   return 1;
 }
 
diff --git a/ltable.c b/ltable.c
index 3fb575a1..8db26bdc 100644
--- a/ltable.c
+++ b/ltable.c
@@ -40,6 +40,27 @@
 
 
 /*
+** Only tables with hash parts larget than LIMFORLAST has a 'lastfree'
+** field that optimizes finding a free slot. Smaller tables do a
+** complete search when looking for a free slot.
+*/
+#define LLIMFORLAST    2  /* log2 of LIMTFORLAST */
+#define LIMFORLAST     twoto(LLIMFORLAST)
+
+/*
+** Union to store an int field ensuring that what follows it in
+** memory is properly aligned to store a TValue.
+*/
+typedef union {
+  int lastfree;
+  char padding[offsetof(struct { int i; TValue v; }, v)];
+} Limbox;
+
+#define haslastfree(t)     ((t)->lsizenode > LLIMFORLAST)
+#define getlastfree(t)     (&((cast(Limbox *, (t)->node) - 1)->lastfree))
+
+
+/*
 ** MAXABITS is the largest integer such that MAXASIZE fits in an
 ** unsigned int.
 */
@@ -369,8 +390,15 @@ int luaH_next (lua_State *L, Table *t, StkId key) {
 
 
 static void freehash (lua_State *L, Table *t) {
-  if (!isdummy(t))
-    luaM_freearray(L, t->node, cast_sizet(sizenode(t)));
+  if (!isdummy(t)) {
+    size_t bsize = sizenode(t) * sizeof(Node);  /* 'node' size in bytes */
+    char *arr = cast_charp(t->node);
+    if (haslastfree(t)) {
+      bsize += sizeof(Limbox);
+      arr -= sizeof(Limbox);
+    }
+    luaM_freearray(L, arr, bsize);
+  }
 }
 
 
@@ -481,7 +509,7 @@ static void setnodevector (lua_State *L, Table *t, unsigned int size) {
   if (size == 0) {  /* no elements to hash part? */
     t->node = cast(Node *, dummynode);  /* use common 'dummynode' */
     t->lsizenode = 0;
-    t->lastfree = NULL;  /* signal that it is using dummy node */
+    setdummy(t);  /* signal that it is using dummy node */
   }
   else {
     int i;
@@ -489,15 +517,22 @@ static void setnodevector (lua_State *L, Table *t, unsigned int size) {
     if (lsize > MAXHBITS || (1u << lsize) > MAXHSIZE)
       luaG_runerror(L, "table overflow");
     size = twoto(lsize);
-    t->node = luaM_newvector(L, size, Node);
+    if (lsize <= LLIMFORLAST)  /* no 'lastfree' field? */
+      t->node = luaM_newvector(L, size, Node);
+    else {
+      size_t bsize = size * sizeof(Node) + sizeof(Limbox);
+      char *node = luaM_newblock(L, bsize);
+      t->node = cast(Node *, node + sizeof(Limbox));
+      *getlastfree(t) = size;  /* all positions are free */
+    }
+    t->lsizenode = cast_byte(lsize);
+    setnodummy(t);
     for (i = 0; i < cast_int(size); i++) {
       Node *n = gnode(t, i);
       gnext(n) = 0;
       setnilkey(n);
       setempty(gval(n));
     }
-    t->lsizenode = cast_byte(lsize);
-    t->lastfree = gnode(t, size);  /* all positions are free */
   }
 }
 
@@ -522,18 +557,21 @@ static void reinsert (lua_State *L, Table *ot, Table *t) {
 
 
 /*
-** Exchange the hash part of 't1' and 't2'.
+** Exchange the hash part of 't1' and 't2'. (In 'flags', only the
+** dummy bit must be exchanged: The 'isrealasize' is not related
+** to the hash part, and the metamethod bits do not change during
+** a resize, so the "real" table can keep their values.)
 */
 static void exchangehashpart (Table *t1, Table *t2) {
   lu_byte lsizenode = t1->lsizenode;
   Node *node = t1->node;
-  Node *lastfree = t1->lastfree;
+  int bitdummy1 = t1->flags & BITDUMMY;
   t1->lsizenode = t2->lsizenode;
   t1->node = t2->node;
-  t1->lastfree = t2->lastfree;
+  t1->flags = (t1->flags & NOTBITDUMMY) | (t2->flags & BITDUMMY);
   t2->lsizenode = lsizenode;
   t2->node = node;
-  t2->lastfree = lastfree;
+  t2->flags = (t2->flags & NOTBITDUMMY) | bitdummy1;
 }
 
 
@@ -557,6 +595,7 @@ void luaH_resize (lua_State *L, Table *t, unsigned int newasize,
   unsigned int oldasize = setlimittosize(t);
   TValue *newarray;
   /* create new hash part with appropriate size into 'newt' */
+  newt.flags = 0;
   setnodevector(L, &newt, nhsize);
   if (newasize < oldasize) {  /* will array shrink? */
     t->alimit = newasize;  /* pretend array has new size... */
@@ -643,11 +682,22 @@ void luaH_free (lua_State *L, Table *t) {
 
 
 static Node *getfreepos (Table *t) {
-  if (!isdummy(t)) {
-    while (t->lastfree > t->node) {
-      t->lastfree--;
-      if (keyisnil(t->lastfree))
-        return t->lastfree;
+  if (haslastfree(t)) {  /* does it have 'lastfree' information? */
+    /* look for a spot before 'lastfree', updating 'lastfree' */
+    while (*getlastfree(t) > 0) {
+      Node *free = gnode(t, --(*getlastfree(t)));
+      if (keyisnil(free))
+        return free;
+    }
+  }
+  else {  /* no 'lastfree' information */
+    if (!isdummy(t)) {
+      int i = sizenode(t);
+      while (i--) {  /* do a linear search */
+        Node *free = gnode(t, i);
+        if (keyisnil(free))
+          return free;
+      }
     }
   }
   return NULL;  /* could not find a free place */
diff --git a/ltable.h b/ltable.h
index 8e689034..30cfc8be 100644
--- a/ltable.h
+++ b/ltable.h
@@ -23,8 +23,18 @@
 #define invalidateTMcache(t)    ((t)->flags &= ~maskflags)
 
 
-/* true when 't' is using 'dummynode' as its hash part */
-#define isdummy(t)              ((t)->lastfree == NULL)
+/*
+** Bit BITDUMMY set in 'flags' means the table is using the dummy node
+** for its hash part.
+*/
+
+#define BITDUMMY                (1 << 6)
+#define NOTBITDUMMY             cast_byte(~BITDUMMY)
+#define isdummy(t)              ((t)->flags & BITDUMMY)
+
+#define setnodummy(t)           ((t)->flags &= NOTBITDUMMY)
+#define setdummy(t)             ((t)->flags |= BITDUMMY)
+
 
 
 /* allocated size for hash nodes */
diff --git a/ltablib.c b/ltablib.c
index e6bc4d04..44d55ef5 100644
--- a/ltablib.c
+++ b/ltablib.c
@@ -230,31 +230,8 @@ typedef unsigned int IdxT;
 ** of a partition. (If you don't want/need this "randomness", ~0 is a
 ** good choice.)
 */
-#if !defined(l_randomizePivot)          /* { */
-
-#include <time.h>
-
-/* size of 'e' measured in number of 'unsigned int's */
-#define sof(e)          (sizeof(e) / sizeof(unsigned int))
-
-/*
-** Use 'time' and 'clock' as sources of "randomness". Because we don't
-** know the types 'clock_t' and 'time_t', we cannot cast them to
-** anything without risking overflows. A safe way to use their values
-** is to copy them to an array of a known type and use the array values.
-*/
-static unsigned int l_randomizePivot (void) {
-  clock_t c = clock();
-  time_t t = time(NULL);
-  unsigned int buff[sof(c) + sof(t)];
-  unsigned int i, rnd = 0;
-  memcpy(buff, &c, sof(c) * sizeof(unsigned int));
-  memcpy(buff + sof(c), &t, sof(t) * sizeof(unsigned int));
-  for (i = 0; i < sof(buff); i++)
-    rnd += buff[i];
-  return rnd;
-}
-
+#if !defined(l_randomizePivot)
+#define l_randomizePivot(L)     luaL_makeseed(L)
 #endif                                  /* } */
 
 
@@ -333,7 +310,7 @@ static IdxT partition (lua_State *L, IdxT lo, IdxT up) {
 */
 static IdxT choosePivot (IdxT lo, IdxT up, unsigned int rnd) {
   IdxT r4 = (up - lo) / 4;  /* range/4 */
-  IdxT p = rnd % (r4 * 2) + (lo + r4);
+  IdxT p = (rnd ^ lo ^ up) % (r4 * 2) + (lo + r4);
   lua_assert(lo + r4 <= p && p <= up - r4);
   return p;
 }
@@ -391,7 +368,7 @@ static void auxsort (lua_State *L, IdxT lo, IdxT up,
       up = p - 1;  /* tail call for [lo .. p - 1]  (lower interval) */
     }
     if ((up - lo) / 128 > n) /* partition too imbalanced? */
-      rnd = l_randomizePivot();  /* try a new randomization */
+      rnd = l_randomizePivot(L);  /* try a new randomization */
   }  /* tail call auxsort(L, lo, up, rnd) */
 }
 
diff --git a/ltests.c b/ltests.c
index 7d184c0d..e218778a 100644
--- a/ltests.c
+++ b/ltests.c
@@ -297,7 +297,7 @@ static int testobjref1 (global_State *g, GCObject *f, GCObject *t) {
   if (isdead(g,t)) return 0;
   if (issweepphase(g))
     return 1;  /* no invariants */
-  else if (g->gckind == KGC_INC)
+  else if (g->gckind != KGC_GEN)
     return !(isblack(f) && iswhite(t));  /* basic incremental invariant */
   else {  /* generational mode */
     if ((getage(f) == G_OLD && isblack(f)) && !isold(t))
@@ -531,7 +531,7 @@ static void checkobject (global_State *g, GCObject *o, int maybedead,
 }
 
 
-static lu_mem checkgraylist (global_State *g, GCObject *o) {
+static l_obj checkgraylist (global_State *g, GCObject *o) {
   int total = 0;  /* count number of elements in the list */
   cast_void(g);  /* better to keep it if we need to print an object */
   while (o) {
@@ -560,7 +560,7 @@ static lu_mem checkgraylist (global_State *g, GCObject *o) {
 /*
 ** Check objects in gray lists.
 */
-static lu_mem checkgrays (global_State *g) {
+static l_obj checkgrays (global_State *g) {
   int total = 0;  /* count number of elements in all lists */
   if (!keepinvariant(g)) return total;
   total += checkgraylist(g, g->gray);
@@ -577,7 +577,7 @@ static lu_mem checkgrays (global_State *g) {
 ** 'count' and check its TESTBIT. (It must have been previously set by
 ** 'checkgraylist'.)
 */
-static void incifingray (global_State *g, GCObject *o, lu_mem *count) {
+static void incifingray (global_State *g, GCObject *o, l_obj *count) {
   if (!keepinvariant(g))
     return;  /* gray lists not being kept in these phases */
   if (o->tt == LUA_VUPVAL) {
@@ -594,10 +594,10 @@ static void incifingray (global_State *g, GCObject *o, lu_mem *count) {
 }
 
 
-static lu_mem checklist (global_State *g, int maybedead, int tof,
+static l_obj checklist (global_State *g, int maybedead, int tof,
   GCObject *newl, GCObject *survival, GCObject *old, GCObject *reallyold) {
   GCObject *o;
-  lu_mem total = 0;  /* number of object that should be in  gray lists */
+  l_obj total = 0;  /* number of object that should be in  gray lists */
   for (o = newl; o != survival; o = o->next) {
     checkobject(g, o, maybedead, G_NEW);
     incifingray(g, o, &total);
@@ -626,8 +626,8 @@ int lua_checkmemory (lua_State *L) {
   global_State *g = G(L);
   GCObject *o;
   int maybedead;
-  lu_mem totalin;  /* total of objects that are in gray lists */
-  lu_mem totalshould;  /* total of objects that should be in gray lists */
+  l_obj totalin;  /* total of objects that are in gray lists */
+  l_obj totalshould;  /* total of objects that should be in gray lists */
   if (keepinvariant(g)) {
     assert(!iswhite(g->mainthread));
     assert(!iswhite(gcvalue(&g->l_registry)));
@@ -999,9 +999,8 @@ static int table_query (lua_State *L) {
   if (i == -1) {
     lua_pushinteger(L, asize);
     lua_pushinteger(L, allocsizenode(t));
-    lua_pushinteger(L, isdummy(t) ? 0 : t->lastfree - t->node);
     lua_pushinteger(L, t->alimit);
-    return 4;
+    return 3;
   }
   else if ((unsigned int)i < asize) {
     lua_pushinteger(L, i);
@@ -1028,6 +1027,16 @@ static int table_query (lua_State *L) {
 }
 
 
+static int query_inc (lua_State *L) {
+  global_State *g = G(L);
+  lua_pushinteger(L, gettotalobjs(g));
+  lua_pushinteger(L, g->GCdebt);
+  lua_pushinteger(L, applygcparam(g, gcpause, 100));
+  lua_pushinteger(L, applygcparam(g, gcstepmul, 100));
+  lua_pushinteger(L, cast(l_obj, 1) << g->gcstepsize);
+  return 5;
+}
+
 static int string_query (lua_State *L) {
   stringtable *tb = &G(L)->strt;
   int s = cast_int(luaL_optinteger(L, 1, 0)) - 1;
@@ -1150,7 +1159,7 @@ static int num2int (lua_State *L) {
 static int newstate (lua_State *L) {
   void *ud;
   lua_Alloc f = lua_getallocf(L, &ud);
-  lua_State *L1 = lua_newstate(f, ud);
+  lua_State *L1 = lua_newstate(f, ud, 0);
   if (L1) {
     lua_atpanic(L1, tpanic);
     lua_pushlightuserdata(L, L1);
@@ -1169,31 +1178,15 @@ static lua_State *getstate (lua_State *L) {
 
 
 static int loadlib (lua_State *L) {
-  static const luaL_Reg libs[] = {
-    {LUA_GNAME, luaopen_base},
-    {"coroutine", luaopen_coroutine},
-    {"debug", luaopen_debug},
-    {"io", luaopen_io},
-    {"os", luaopen_os},
-    {"math", luaopen_math},
-    {"string", luaopen_string},
-    {"table", luaopen_table},
-    {"T", luaB_opentests},
-    {NULL, NULL}
-  };
   lua_State *L1 = getstate(L);
-  int i;
-  luaL_requiref(L1, "package", luaopen_package, 0);
+  int what = luaL_checkinteger(L, 2);
+  luaL_openselectedlibs(L1, what);
+  luaL_requiref(L1, "T", luaB_opentests, 0);
   lua_assert(lua_type(L1, -1) == LUA_TTABLE);
   /* 'requiref' should not reload module already loaded... */
-  luaL_requiref(L1, "package", NULL, 1);  /* seg. fault if it reloads */
+  luaL_requiref(L1, "T", NULL, 1);  /* seg. fault if it reloads */
   /* ...but should return the same module */
   lua_assert(lua_compare(L1, -1, -2, LUA_OPEQ));
-  luaL_getsubtable(L1, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);
-  for (i = 0; libs[i].name; i++) {
-    lua_pushcfunction(L1, libs[i].func);
-    lua_setfield(L1, -2, libs[i].name);
-  }
   return 0;
 }
 
@@ -1259,7 +1252,7 @@ static int checkpanic (lua_State *L) {
   lua_Alloc f = lua_getallocf(L, &ud);
   b.paniccode = luaL_optstring(L, 2, "");
   b.L = L;
-  L1 = lua_newstate(f, ud);  /* create new state */
+  L1 = lua_newstate(f, ud, 0);  /* create new state */
   if (L1 == NULL) {  /* error? */
     lua_pushnil(L);
     return 1;
@@ -1934,6 +1927,7 @@ static const struct luaL_Reg tests_funcs[] = {
   {"pushuserdata", pushuserdata},
   {"querystr", string_query},
   {"querytab", table_query},
+  {"queryinc", query_inc},
   {"ref", tref},
   {"resume", coresume},
   {"s2d", s2d},
diff --git a/ltests.h b/ltests.h
index ec520498..da773d6e 100644
--- a/ltests.h
+++ b/ltests.h
@@ -102,9 +102,10 @@ LUA_API void *debug_realloc (void *ud, void *block,
                              size_t osize, size_t nsize);
 
 #if defined(lua_c)
-#define luaL_newstate()         lua_newstate(debug_realloc, &l_memcontrol)
-#define luaL_openlibs(L)  \
-  { (luaL_openlibs)(L); \
+#define luaL_newstate()  \
+        lua_newstate(debug_realloc, &l_memcontrol, luaL_makeseed(NULL))
+#define luai_openlibs(L)  \
+  {  luaL_openlibs(L); \
      luaL_requiref(L, "T", luaB_opentests, 1); \
      lua_pop(L, 1); }
 #endif
diff --git a/ltm.c b/ltm.c
index 07a06081..8e0d2222 100644
--- a/ltm.c
+++ b/ltm.c
@@ -260,7 +260,7 @@ void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
   int nextra = ci->u.l.nextraargs;
   if (wanted < 0) {
     wanted = nextra;  /* get all extra arguments available */
-    checkstackGCp(L, nextra, where);  /* ensure stack space */
+    checkstackp(L, nextra, where);  /* ensure stack space */
     L->top.p = where + nextra;  /* next instruction will need top */
   }
   for (i = 0; i < wanted && i < nextra; i++)
diff --git a/ltm.h b/ltm.h
index 73b833c6..f3872655 100644
--- a/ltm.h
+++ b/ltm.h
@@ -48,8 +48,8 @@ typedef enum {
 /*
 ** Mask with 1 in all fast-access methods. A 1 in any of these bits
 ** in the flag of a (meta)table means the metatable does not have the
-** corresponding metamethod field. (Bit 7 of the flag is used for
-** 'isrealasize'.)
+** corresponding metamethod field. (Bit 6 of the flag indicates that
+** the table is using the dummy node; bit 7 is used for 'isrealasize'.)
 */
 #define maskflags       (~(~0u << (TM_EQ + 1)))
 
diff --git a/lua.c b/lua.c
index 3af5ce6a..1e884b07 100644
--- a/lua.c
+++ b/lua.c
@@ -617,6 +617,10 @@ static void doREPL (lua_State *L) {
 
 /* }================================================================== */
 
+#if !defined(luai_openlibs)
+#define luai_openlibs(L)        luaL_openlibs(L)
+#endif
+
 
 /*
 ** Main body of stand-alone interpreter (to be called in protected mode).
@@ -639,7 +643,7 @@ static int pmain (lua_State *L) {
     lua_pushboolean(L, 1);  /* signal for libraries to ignore env. vars. */
     lua_setfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
   }
-  luaL_openlibs(L);  /* open standard libraries */
+  luai_openlibs(L);  /* open standard libraries */
   createargtable(L, argv, argc, script);  /* create table 'arg' */
   lua_gc(L, LUA_GCRESTART);  /* start GC... */
   lua_gc(L, LUA_GCGEN, 0, 0);  /* ...in generational mode */
diff --git a/lua.h b/lua.h
index 040cc8e4..699b7ca7 100644
--- a/lua.h
+++ b/lua.h
@@ -18,8 +18,8 @@
 
 
 #define LUA_VERSION_MAJOR_N     5
-#define LUA_VERSION_MINOR_N     4
-#define LUA_VERSION_RELEASE_N   6
+#define LUA_VERSION_MINOR_N     5
+#define LUA_VERSION_RELEASE_N   0
 
 #define LUA_VERSION_NUM  (LUA_VERSION_MAJOR_N * 100 + LUA_VERSION_MINOR_N)
 #define LUA_VERSION_RELEASE_NUM  (LUA_VERSION_NUM * 100 + LUA_VERSION_RELEASE_N)
@@ -159,11 +159,11 @@ extern const char lua_ident[];
 /*
 ** state manipulation
 */
-LUA_API lua_State *(lua_newstate) (lua_Alloc f, void *ud);
+LUA_API lua_State *(lua_newstate) (lua_Alloc f, void *ud,
+                                   unsigned int seed);
 LUA_API void       (lua_close) (lua_State *L);
 LUA_API lua_State *(lua_newthread) (lua_State *L);
 LUA_API int        (lua_closethread) (lua_State *L, lua_State *from);
-LUA_API int        (lua_resetthread) (lua_State *L);  /* Deprecated! */
 
 LUA_API lua_CFunction (lua_atpanic) (lua_State *L, lua_CFunction panicf);
 
@@ -425,6 +425,8 @@ LUA_API void (lua_closeslot) (lua_State *L, int idx);
 
 #define LUA_NUMTAGS             LUA_NUMTYPES
 
+#define lua_resetthread(L)      lua_closethread(L,NULL)
+
 /* }============================================================== */
 
 /*
diff --git a/lualib.h b/lualib.h
index 26255290..e124cf1b 100644
--- a/lualib.h
+++ b/lualib.h
@@ -14,39 +14,52 @@
 /* version suffix for environment variable names */
 #define LUA_VERSUFFIX          "_" LUA_VERSION_MAJOR "_" LUA_VERSION_MINOR
 
-
+#define LUA_GK          1
 LUAMOD_API int (luaopen_base) (lua_State *L);
 
+#define LUA_LOADLIBNAME "package"
+#define LUA_LOADLIBK    (LUA_GK << 1)
+LUAMOD_API int (luaopen_package) (lua_State *L);
+
+
 #define LUA_COLIBNAME   "coroutine"
+#define LUA_COLIBK      (LUA_LOADLIBK << 1)
 LUAMOD_API int (luaopen_coroutine) (lua_State *L);
 
-#define LUA_TABLIBNAME  "table"
-LUAMOD_API int (luaopen_table) (lua_State *L);
+#define LUA_DBLIBNAME   "debug"
+#define LUA_DBLIBK      (LUA_COLIBK << 1)
+LUAMOD_API int (luaopen_debug) (lua_State *L);
 
 #define LUA_IOLIBNAME   "io"
+#define LUA_IOLIBK      (LUA_DBLIBK << 1)
 LUAMOD_API int (luaopen_io) (lua_State *L);
 
+#define LUA_MATHLIBNAME "math"
+#define LUA_MATHLIBK    (LUA_IOLIBK << 1)
+LUAMOD_API int (luaopen_math) (lua_State *L);
+
 #define LUA_OSLIBNAME   "os"
+#define LUA_OSLIBK      (LUA_MATHLIBK << 1)
 LUAMOD_API int (luaopen_os) (lua_State *L);
 
 #define LUA_STRLIBNAME  "string"
+#define LUA_STRLIBK     (LUA_OSLIBK << 1)
 LUAMOD_API int (luaopen_string) (lua_State *L);
 
+#define LUA_TABLIBNAME  "table"
+#define LUA_TABLIBK     (LUA_STRLIBK << 1)
+LUAMOD_API int (luaopen_table) (lua_State *L);
+
 #define LUA_UTF8LIBNAME "utf8"
+#define LUA_UTF8LIBK    (LUA_TABLIBK << 1)
 LUAMOD_API int (luaopen_utf8) (lua_State *L);
 
-#define LUA_MATHLIBNAME "math"
-LUAMOD_API int (luaopen_math) (lua_State *L);
-
-#define LUA_DBLIBNAME   "debug"
-LUAMOD_API int (luaopen_debug) (lua_State *L);
-
-#define LUA_LOADLIBNAME "package"
-LUAMOD_API int (luaopen_package) (lua_State *L);
 
+/* open selected libraries */
+LUALIB_API void (luaL_openselectedlibs) (lua_State *L, int what);
 
-/* open all previous libraries */
-LUALIB_API void (luaL_openlibs) (lua_State *L);
+/* open all libraries */
+#define luaL_openlibs(L)        luaL_openselectedlibs(L, ~0)
 
 
 #endif
diff --git a/lundump.c b/lundump.c
index 02aed64f..1df15e53 100644
--- a/lundump.c
+++ b/lundump.c
@@ -21,6 +21,7 @@
 #include "lmem.h"
 #include "lobject.h"
 #include "lstring.h"
+#include "ltable.h"
 #include "lundump.h"
 #include "lzio.h"
 
@@ -34,6 +35,8 @@ typedef struct {
   lua_State *L;
   ZIO *Z;
   const char *name;
+  Table *h;  /* list for string reuse */
+  lua_Integer nstr;  /* number of strings in the list */
 } LoadState;
 
 
@@ -110,10 +113,16 @@ static lua_Integer loadInteger (LoadState *S) {
 static TString *loadStringN (LoadState *S, Proto *p) {
   lua_State *L = S->L;
   TString *ts;
+  TValue sv;
   size_t size = loadSize(S);
   if (size == 0)  /* no string? */
     return NULL;
-  else if (--size <= LUAI_MAXSHORTLEN) {  /* short string? */
+  else if (size == 1) {  /* previously saved string? */
+    int idx = loadInt(S);  /* get its index */
+    const TValue *stv = luaH_getint(S->h, idx);
+    return tsvalue(stv);
+  }
+  else if (size -= 2, size <= LUAI_MAXSHORTLEN) {  /* short string? */
     char buff[LUAI_MAXSHORTLEN];
     loadVector(S, buff, size);  /* load string into buffer */
     ts = luaS_newlstr(L, buff, size);  /* create string */
@@ -126,6 +135,10 @@ static TString *loadStringN (LoadState *S, Proto *p) {
     L->top.p--;  /* pop string */
   }
   luaC_objbarrier(L, p, ts);
+  S->nstr++;  /* add string to list of saved strings */
+  setsvalue(L, &sv, ts);
+  luaH_setint(L, S->h, S->nstr, &sv);
+  luaC_objbarrierback(L, obj2gco(S->h), ts);
   return ts;
 }
 
@@ -149,7 +162,7 @@ static void loadCode (LoadState *S, Proto *f) {
 }
 
 
-static void loadFunction(LoadState *S, Proto *f, TString *psource);
+static void loadFunction(LoadState *S, Proto *f);
 
 
 static void loadConstants (LoadState *S, Proto *f) {
@@ -198,7 +211,7 @@ static void loadProtos (LoadState *S, Proto *f) {
   for (i = 0; i < n; i++) {
     f->p[i] = luaF_newproto(S->L);
     luaC_objbarrier(S->L, f, f->p[i]);
-    loadFunction(S, f->p[i], f->source);
+    loadFunction(S, f->p[i]);
   }
 }
 
@@ -255,10 +268,8 @@ static void loadDebug (LoadState *S, Proto *f) {
 }
 
 
-static void loadFunction (LoadState *S, Proto *f, TString *psource) {
+static void loadFunction (LoadState *S, Proto *f) {
   f->source = loadStringN(S, f);
-  if (f->source == NULL)  /* no source in dump? */
-    f->source = psource;  /* reuse parent's source */
   f->linedefined = loadInt(S);
   f->lastlinedefined = loadInt(S);
   f->numparams = loadByte(S);
@@ -325,11 +336,16 @@ LClosure *luaU_undump(lua_State *L, ZIO *Z, const char *name) {
   cl = luaF_newLclosure(L, loadByte(&S));
   setclLvalue2s(L, L->top.p, cl);
   luaD_inctop(L);
+  S.h = luaH_new(L);  /* create list of saved strings */
+  S.nstr = 0;
+  sethvalue2s(L, L->top.p, S.h);  /* anchor it */
+  luaD_inctop(L);
   cl->p = luaF_newproto(L);
   luaC_objbarrier(L, cl, cl->p);
-  loadFunction(&S, cl->p, NULL);
+  loadFunction(&S, cl->p);
   lua_assert(cl->nupvalues == cl->p->sizeupvalues);
   luai_verifycode(L, cl->p);
+  L->top.p--;  /* pop table */
   return cl;
 }
 
diff --git a/lundump.h b/lundump.h
index f3748a99..7def905b 100644
--- a/lundump.h
+++ b/lundump.h
@@ -31,6 +31,6 @@ LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, const char* name);
 
 /* dump one chunk; from ldump.c */
 LUAI_FUNC int luaU_dump (lua_State* L, const Proto* f, lua_Writer w,
-                         void* data, int strip);
+                         void* data, int strip, Table *h);
 
 #endif
diff --git a/lvm.c b/lvm.c
index 2b437bdf..a3128c3d 100644
--- a/lvm.c
+++ b/lvm.c
@@ -196,12 +196,15 @@ static int forlimit (lua_State *L, lua_Integer init, const TValue *lim,
 
 /*
 ** Prepare a numerical for loop (opcode OP_FORPREP).
+** Before execution, stack is as follows:
+**   ra     : initial value
+**   ra + 1 : limit
+**   ra + 2 : step
 ** Return true to skip the loop. Otherwise,
 ** after preparation, stack will be as follows:
-**   ra : internal index (safe copy of the control variable)
-**   ra + 1 : loop counter (integer loops) or limit (float loops)
-**   ra + 2 : step
-**   ra + 3 : control variable
+**   ra     : loop counter (integer loops) or limit (float loops)
+**   ra + 1 : step
+**   ra + 2 : control variable
 */
 static int forprep (lua_State *L, StkId ra) {
   TValue *pinit = s2v(ra);
@@ -213,7 +216,6 @@ static int forprep (lua_State *L, StkId ra) {
     lua_Integer limit;
     if (step == 0)
       luaG_runerror(L, "'for' step is zero");
-    setivalue(s2v(ra + 3), init);  /* control variable */
     if (forlimit(L, init, plimit, &limit, step))
       return 1;  /* skip the loop */
     else {  /* prepare loop counter */
@@ -228,9 +230,10 @@ static int forprep (lua_State *L, StkId ra) {
         /* 'step+1' avoids negating 'mininteger' */
         count /= l_castS2U(-(step + 1)) + 1u;
       }
-      /* store the counter in place of the limit (which won't be
-         needed anymore) */
-      setivalue(plimit, l_castU2S(count));
+      /* use 'chgivalue' for places that for sure had integers */
+      chgivalue(s2v(ra), l_castU2S(count));  /* change init to count */
+      setivalue(s2v(ra + 1), step);  /* change limit to step */
+      chgivalue(s2v(ra + 2), init);  /* change step to init */
     }
   }
   else {  /* try making all values floats */
@@ -247,11 +250,10 @@ static int forprep (lua_State *L, StkId ra) {
                             : luai_numlt(init, limit))
       return 1;  /* skip the loop */
     else {
-      /* make sure internal values are all floats */
-      setfltvalue(plimit, limit);
-      setfltvalue(pstep, step);
-      setfltvalue(s2v(ra), init);  /* internal index */
-      setfltvalue(s2v(ra + 3), init);  /* control variable */
+      /* make sure all values are floats */
+      setfltvalue(s2v(ra), limit);
+      setfltvalue(s2v(ra + 1), step);
+      setfltvalue(s2v(ra + 2), init);  /* control variable */
     }
   }
   return 0;
@@ -264,14 +266,13 @@ static int forprep (lua_State *L, StkId ra) {
 ** written online with opcode OP_FORLOOP, for performance.)
 */
 static int floatforloop (StkId ra) {
-  lua_Number step = fltvalue(s2v(ra + 2));
-  lua_Number limit = fltvalue(s2v(ra + 1));
-  lua_Number idx = fltvalue(s2v(ra));  /* internal index */
+  lua_Number step = fltvalue(s2v(ra + 1));
+  lua_Number limit = fltvalue(s2v(ra));
+  lua_Number idx = fltvalue(s2v(ra + 2));  /* control variable */
   idx = luai_numadd(L, idx, step);  /* increment index */
   if (luai_numlt(0, step) ? luai_numle(idx, limit)
                           : luai_numle(limit, idx)) {
-    chgfltvalue(s2v(ra), idx);  /* update internal index */
-    setfltvalue(s2v(ra + 3), idx);  /* and control variable */
+    chgfltvalue(s2v(ra + 2), idx);  /* update control variable */
     return 1;  /* jump back */
   }
   else
@@ -1787,15 +1788,14 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       }
       vmcase(OP_FORLOOP) {
         StkId ra = RA(i);
-        if (ttisinteger(s2v(ra + 2))) {  /* integer loop? */
-          lua_Unsigned count = l_castS2U(ivalue(s2v(ra + 1)));
+        if (ttisinteger(s2v(ra + 1))) {  /* integer loop? */
+          lua_Unsigned count = l_castS2U(ivalue(s2v(ra)));
           if (count > 0) {  /* still more iterations? */
-            lua_Integer step = ivalue(s2v(ra + 2));
-            lua_Integer idx = ivalue(s2v(ra));  /* internal index */
-            chgivalue(s2v(ra + 1), count - 1);  /* update counter */
+            lua_Integer step = ivalue(s2v(ra + 1));
+            lua_Integer idx = ivalue(s2v(ra + 2));  /* control variable */
+            chgivalue(s2v(ra), count - 1);  /* update counter */
             idx = intop(+, idx, step);  /* add step to index */
-            chgivalue(s2v(ra), idx);  /* update internal index */
-            setivalue(s2v(ra + 3), idx);  /* and control variable */
+            chgivalue(s2v(ra + 2), idx);  /* update control variable */
             pc -= GETARG_Bx(i);  /* jump back */
           }
         }
@@ -1812,26 +1812,38 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_TFORPREP) {
+       /* before: 'ra' has the iterator function, 'ra + 1' has the state,
+          'ra + 2' has the initial value for the control variable, and
+          'ra + 3' has the closing variable. This opcode then swaps the
+          control and the closing variables and marks the closing variable
+          as to-be-closed.
+       */
        StkId ra = RA(i);
-        /* create to-be-closed upvalue (if needed) */
-        halfProtect(luaF_newtbcupval(L, ra + 3));
-        pc += GETARG_Bx(i);
-        i = *(pc++);  /* go to next instruction */
+       TValue temp;  /* to swap control and closing variables */
+       setobj(L, &temp, s2v(ra + 3));
+       setobjs2s(L, ra + 3, ra + 2);
+       setobj2s(L, ra + 2, &temp);
+        /* create to-be-closed upvalue (if closing var. is not nil) */
+        halfProtect(luaF_newtbcupval(L, ra + 2));
+        pc += GETARG_Bx(i);  /* go to end of the loop */
+        i = *(pc++);  /* fetch next instruction */
         lua_assert(GET_OPCODE(i) == OP_TFORCALL && ra == RA(i));
         goto l_tforcall;
       }
       vmcase(OP_TFORCALL) {
        l_tforcall: {
-        StkId ra = RA(i);
         /* 'ra' has the iterator function, 'ra + 1' has the state,
-           'ra + 2' has the control variable, and 'ra + 3' has the
-           to-be-closed variable. The call will use the stack after
-           these values (starting at 'ra + 4')
+           'ra + 2' has the closing variable, and 'ra + 3' has the control
+           variable. The call will use the stack starting at 'ra + 3',
+           so that it preserves the first three values, and the first
+           return will be the new value for the control variable.
         */
-        /* push function, state, and control variable */
-        memcpy(ra + 4, ra, 3 * sizeof(*ra));
-        L->top.p = ra + 4 + 3;
-        ProtectNT(luaD_call(L, ra + 4, GETARG_C(i)));  /* do the call */
+        StkId ra = RA(i);
+        setobjs2s(L, ra + 5, ra + 3);  /* copy the control variable */
+        setobjs2s(L, ra + 4, ra + 1);  /* copy state */
+        setobjs2s(L, ra + 3, ra);  /* copy function */
+        L->top.p = ra + 3 + 3;
+        ProtectNT(luaD_call(L, ra + 3, GETARG_C(i)));  /* do the call */
         updatestack(ci);  /* stack may have changed */
         i = *(pc++);  /* go to next instruction */
         lua_assert(GET_OPCODE(i) == OP_TFORLOOP && ra == RA(i));
@@ -1840,10 +1852,8 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       vmcase(OP_TFORLOOP) {
        l_tforloop: {
         StkId ra = RA(i);
-        if (!ttisnil(s2v(ra + 4))) {  /* continue loop? */
-          setobjs2s(L, ra + 2, ra + 4);  /* save control variable */
+        if (!ttisnil(s2v(ra + 3)))  /* continue loop? */
           pc -= GETARG_Bx(i);  /* jump back */
-        }
         vmbreak;
       }}
       vmcase(OP_SETLIST) {
diff --git a/manual/manual.of b/manual/manual.of
index f8d8ddd4..1e219f9a 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -1467,7 +1467,7 @@ It has the following syntax:
   exp @bnfter{,} exp @bnfopt{@bnfter{,} exp} @Rw{do} block @Rw{end}}
 }
 The given identifier (@bnfNter{Name}) defines the control variable,
-which is a new variable local to the loop body (@emph{block}).
+which is a new read-only variable local to the loop body (@emph{block}).
 
 The loop starts by evaluating once the three control expressions.
 Their values are called respectively
@@ -1499,11 +1499,6 @@ For integer loops,
 the control variable never wraps around;
 instead, the loop ends in case of an overflow.
 
-You should not change the value of the control variable
-during the loop.
-If you need its value after the loop,
-assign it to another variable before exiting the loop.
-
 }
 
 @sect4{@title{The generic @Rw{for} loop}
@@ -1526,7 +1521,8 @@ for @rep{var_1}, @Cdots, @rep{var_n} in @rep{explist} do @rep{body} end
 works as follows.
 
 The names @rep{var_i} declare loop variables local to the loop body.
-The first of these variables is the @emph{control variable}.
+The first of these variables is the @emph{control variable},
+which is a read-only variable.
 
 The loop starts by evaluating @rep{explist}
 to produce four values:
@@ -1550,9 +1546,6 @@ to-be-closed variable @see{to-be-closed},
 which can be used to release resources when the loop ends.
 Otherwise, it does not interfere with the loop.
 
-You should not change the value of the control variable
-during the loop.
-
 }
 
 }
@@ -1586,7 +1579,8 @@ Each variable name may be postfixed by an attribute
 @producname{attrib}@producbody{@bnfopt{@bnfter{<} @bnfNter{Name} @bnfter{>}}}
 }
 There are two possible attributes:
-@id{const}, which declares a @x{constant variable},
+@id{const}, which declares a @emph{constant} or @emph{read-only} variable,
+@index{constant variable}
 that is, a variable that cannot be assigned to
 after its initialization;
 and @id{close}, which declares a to-be-closed variable @see{to-be-closed}.
@@ -3671,7 +3665,8 @@ Other upvalues are initialized with @nil.
 
 }
 
-@APIEntry{lua_State *lua_newstate (lua_Alloc f, void *ud);|
+@APIEntry{lua_State *lua_newstate (lua_Alloc f, void *ud,
+                                   unsigned int seed);|
 @apii{0,0,-}
 
 Creates a new independent state and returns its main thread.
@@ -3682,6 +3677,8 @@ Lua will do all memory allocation for this state
 through this function @seeF{lua_Alloc}.
 The second argument, @id{ud}, is an opaque pointer that Lua
 passes to the allocator in every call.
+The third argument, @id{seed}, is a seed for the hashing of
+strings when they are used as table keys.
 
 }
 
@@ -5737,6 +5734,16 @@ it does not run it.
 
 }
 
+@APIEntry{unsigned int luaL_makeseed (lua_State *L);|
+@apii{0,0,-}
+
+Returns a value with a weak attempt for randomness.
+(It produces that value based on the current date and time
+and the address of an internal variable,
+in case the machine has Address Space Layout Randomization.)
+
+}
+
 
 @APIEntry{void luaL_newlib (lua_State *L, const luaL_Reg l[]);|
 @apii{0,1,m}
@@ -6909,9 +6916,9 @@ including if necessary a path and an extension.
 (which may depend on the @N{C compiler} and linker used).
 
 This functionality is not supported by @N{ISO C}.
-As such, it is only available on some platforms
-(Windows, Linux, Mac OS X, Solaris, BSD,
-plus other Unix systems that support the @id{dlfcn} standard).
+As such, @id{loadlib} is only available on some platforms:
+Linux, Windows, Mac OS X, Solaris, BSD,
+plus other Unix systems that support the @id{dlfcn} standard.
 
 This function is inherently insecure,
 as it allows Lua to call any function in any readable dynamic
@@ -8109,7 +8116,7 @@ different sequences of results each time the program runs.
 
 When called with at least one argument,
 the integer parameters @id{x} and @id{y} are
-joined into a 128-bit @emphx{seed} that
+joined into a @emphx{seed} that
 is used to reinitialize the pseudo-random generator;
 equal seeds produce equal sequences of numbers.
 The default for @id{y} is zero.
@@ -9128,7 +9135,7 @@ is a more portable solution.
 @simplesect{
 
 Here we list the incompatibilities that you may find when moving a program
-from @N{Lua 5.3} to @N{Lua 5.4}.
+from @N{Lua 5.4} to @N{Lua 5.5}.
 
 You can avoid some incompatibilities by compiling Lua with
 appropriate options (see file @id{luaconf.h}).
@@ -9165,51 +9172,9 @@ change between versions.
 @itemize{
 
 @item{
-The coercion of strings to numbers in
-arithmetic and bitwise operations
-has been removed from the core language.
-The string library does a similar job
-for arithmetic (but not for bitwise) operations
-using the string metamethods.
-However, unlike in previous versions,
-the new implementation preserves the implicit type of the numeral
-in the string.
-For instance, the result of @T{"1" + "2"} now is an integer,
-not a float.
-}
-
-@item{
-Literal decimal integer constants that overflow are read as floats,
-instead of wrapping around.
-You can use hexadecimal notation for such constants if you
-want the old behavior
-(reading them as integers with wrap around).
-}
-
-@item{
-The use of the @idx{__lt} metamethod to emulate @idx{__le}
-has been removed.
-When needed, this metamethod must be explicitly defined.
-}
-
-@item{
-The semantics of the numerical @Rw{for} loop
-over integers changed in some details.
-In particular, the control variable never wraps around.
-}
-
-@item{
-A label for a @Rw{goto} cannot be declared where a label with the same
-name is visible, even if this other label is declared in an enclosing
-block.
-}
-
-@item{
-When finalizing an object,
-Lua does not ignore @idx{__gc} metamethods that are not functions.
-Any value will be called, if present.
-(Non-callable values will generate a warning,
-like any other error when calling a finalizer.)
+The control variable in @Rw{for} loops are read only.
+If you need to change it,
+declare a local variable with the same name in the loop body.
 }
 
 }
@@ -9220,39 +9185,6 @@ like any other error when calling a finalizer.)
 @itemize{
 
 @item{
-The function @Lid{print} does not call @Lid{tostring}
-to format its arguments;
-instead, it has this functionality hardwired.
-You should use @idx{__tostring} to modify how values are printed.
-}
-
-@item{
-The pseudo-random number generator used by the function @Lid{math.random}
-now starts with a somewhat random seed.
-Moreover, it uses a different algorithm.
-}
-
-@item{
-By default, the decoding functions in the @Lid{utf8} library
-do not accept surrogates as valid code points.
-An extra parameter in these functions makes them more permissive.
-}
-
-@item{
-The options @St{setpause} and @St{setstepmul}
-of the function @Lid{collectgarbage} are deprecated.
-You should use the new option @St{incremental} to set them.
-}
-
-@item{
-The function @Lid{io.lines} now returns four values,
-instead of just one.
-That can be a problem when it is used as the sole
-argument to another function that has optional parameters,
-such as in @T{load(io.lines(filename, "L"))}.
-To fix that issue,
-you can wrap the call into parentheses,
-to adjust its number of results to one.
 }
 
 }
@@ -9264,46 +9196,6 @@ to adjust its number of results to one.
 @itemize{
 
 @item{
-Full userdata now has an arbitrary number of associated user values.
-Therefore, the functions @id{lua_newuserdata},
-@id{lua_setuservalue}, and @id{lua_getuservalue} were
-replaced by @Lid{lua_newuserdatauv},
-@Lid{lua_setiuservalue}, and @Lid{lua_getiuservalue},
-which have an extra argument.
-
-For compatibility, the old names still work as macros assuming
-one single user value.
-Note, however, that userdata with zero user values
-are more efficient memory-wise.
-}
-
-@item{
-The function @Lid{lua_resume} has an extra parameter.
-This out parameter returns the number of values on
-the top of the stack that were yielded or returned by the coroutine.
-(In previous versions,
-those values were the entire stack.)
-}
-
-@item{
-The function @Lid{lua_version} returns the version number,
-instead of an address of the version number.
-The Lua core should work correctly with libraries using their
-own static copies of the same core,
-so there is no need to check whether they are using the same
-address space.
-}
-
-@item{
-The constant @id{LUA_ERRGCMM} was removed.
-Errors in finalizers are never propagated;
-instead, they generate a warning.
-}
-
-@item{
-The options @idx{LUA_GCSETPAUSE} and @idx{LUA_GCSETSTEPMUL}
-of the function @Lid{lua_gc} are deprecated.
-You should use the new option @id{LUA_GCINC} to set them.
 }
 
 }
diff --git a/testes/all.lua b/testes/all.lua
index 5df0ff9b..3c1ff5c7 100644
--- a/testes/all.lua
+++ b/testes/all.lua
@@ -3,7 +3,7 @@
 -- See Copyright Notice at the end of this file
 
 
-local version = "Lua 5.4"
+local version = "Lua 5.5"
 if _VERSION ~= version then
   io.stderr:write("This test suite is for ", version,
                   ", not for ", _VERSION, "\nExiting tests")
diff --git a/testes/api.lua b/testes/api.lua
index 752ff18f..dece98f5 100644
--- a/testes/api.lua
+++ b/testes/api.lua
@@ -1046,10 +1046,12 @@ assert(a == nil and c == 2)   -- 2 == run-time error
 a, b, c = T.doremote(L1, "return a+")
 assert(a == nil and c == 3 and type(b) == "string")   -- 3 == syntax error
 
-T.loadlib(L1)
+T.loadlib(L1, 2)    -- load only 'package'
 a, b, c = T.doremote(L1, [[
   string = require'string'
-  a = require'_G'; assert(a == _G and require("_G") == a)
+  local initialG = _G   -- not loaded yet
+  local a = require'_G'; assert(a == _G and require("_G") == a)
+  assert(initialG == nil and io == nil)   -- now we have 'assert'
   io = require'io'; assert(type(io.read) == "function")
   assert(require("io") == io)
   a = require'table'; assert(type(a.insert) == "function")
@@ -1063,7 +1065,7 @@ T.closestate(L1);
 
 
 L1 = T.newstate()
-T.loadlib(L1)
+T.loadlib(L1, 0)
 T.doremote(L1, "a = {}")
 T.testC(L1, [[getglobal "a"; pushstring "x"; pushint 1;
              settable -3]])
@@ -1446,10 +1448,10 @@ end
 
 do   -- garbage collection with no extra memory
   local L = T.newstate()
-  T.loadlib(L)
+  T.loadlib(L, 1 | 2)   -- load _G and 'package'
   local res = (T.doremote(L, [[
-    _ENV = require"_G"
-    local T = require"T"
+    _ENV = _G
+    assert(string == nil)
     local a = {}
     for i = 1, 1000 do a[i] = 'i' .. i end    -- grow string table
     local stsize, stuse = T.querystr()
diff --git a/testes/attrib.lua b/testes/attrib.lua
index 458488a8..9054e0b6 100644
--- a/testes/attrib.lua
+++ b/testes/attrib.lua
@@ -236,7 +236,7 @@ package.path = oldpath
 local fname = "file_does_not_exist2"
 local m, err = pcall(require, fname)
 for t in string.gmatch(package.path..";"..package.cpath, "[^;]+") do
-  t = string.gsub(t, "?", fname)
+  local t = string.gsub(t, "?", fname)
   assert(string.find(err, t, 1, true))
 end
 
diff --git a/testes/calls.lua b/testes/calls.lua
index 2d562a24..559ca935 100644
--- a/testes/calls.lua
+++ b/testes/calls.lua
@@ -346,7 +346,7 @@ do   -- another bug (since 5.2)
   -- corrupted binary dump: list of upvalue names is larger than number
   -- of upvalues, overflowing the array of upvalues.
   local code =
-   "\x1b\x4c\x75\x61\x54\x00\x19\x93\x0d\x0a\x1a\x0a\x04\x08\x08\x78\x56\z
+   "\x1b\x4c\x75\x61\x55\x00\x19\x93\x0d\x0a\x1a\x0a\x04\x08\x08\x78\x56\z
     \x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x28\x77\x40\x00\x86\x40\z
     \x74\x65\x6d\x70\x81\x81\x01\x00\x02\x82\x48\x00\x02\x00\xc7\x00\x01\z
     \x00\x80\x80\x80\x82\x00\x00\x80\x81\x82\x78\x80\x82\x81\x86\x40\x74\z
@@ -468,7 +468,7 @@ print("testing binary chunks")
 do
   local header = string.pack("c4BBc6BBB",
     "\27Lua",                                  -- signature
-    0x54,                                      -- version 5.4 (0x54)
+    0x55,                                      -- version 5.5 (0x55)
     0,                                         -- format
     "\x19\x93\r\n\x1a\n",                      -- data
     4,                                         -- size of instruction
@@ -507,5 +507,30 @@ do
   end
 end
 
+
+do   -- check reuse of strings in dumps
+  local str = "|" .. string.rep("X", 50) .. "|"
+  local foo = load(string.format([[
+    local str <const> = "%s"
+    return {
+      function () return str end,
+      function () return str end,
+      function () return str end
+    }
+  ]], str))
+  -- count occurrences of 'str' inside the dump
+  local dump = string.dump(foo)
+  local _, count = string.gsub(dump, str, {})
+  -- there should be only two occurrences:
+  -- one inside the source, other the string itself.
+  assert(count == 2)
+
+  if T then  -- check reuse of strings in undump
+    local funcs = load(dump)()
+    assert(string.format("%p", T.listk(funcs[1])[1]) ==
+           string.format("%p", T.listk(funcs[3])[1]))
+  end
+end
+
 print('OK')
 return deep
diff --git a/testes/closure.lua b/testes/closure.lua
index ea038e82..de1b54ec 100644
--- a/testes/closure.lua
+++ b/testes/closure.lua
@@ -60,32 +60,29 @@ end
 -- testing closures with 'for' control variable
 a = {}
 for i=1,10 do
-  a[i] = {set = function(x) i=x end, get = function () return i end}
+  a[i] = function () return i end
   if i == 3 then break end
 end
 assert(a[4] == undef)
-a[1].set(10)
-assert(a[2].get() == 2)
-a[2].set('a')
-assert(a[3].get() == 3)
-assert(a[2].get() == 'a')
+assert(a[2]() == 2)
+assert(a[3]() == 3)
 
 a = {}
 local t = {"a", "b"}
 for i = 1, #t do
   local k = t[i]
-  a[i] = {set = function(x, y) i=x; k=y end,
+  a[i] = {set = function(x) k=x end,
           get = function () return i, k end}
   if i == 2 then break end
 end
-a[1].set(10, 20)
+a[1].set(10)
 local r,s = a[2].get()
 assert(r == 2 and s == 'b')
 r,s = a[1].get()
-assert(r == 10 and s == 20)
-a[2].set('a', 'b')
+assert(r == 1 and s == 10)
+a[2].set('a')
 r,s = a[2].get()
-assert(r == "a" and s == "b")
+assert(r == 2 and s == "a")
 
 
 -- testing closures with 'for' control variable x break
diff --git a/testes/coroutine.lua b/testes/coroutine.lua
index de7e46fb..990da8c4 100644
--- a/testes/coroutine.lua
+++ b/testes/coroutine.lua
@@ -703,7 +703,7 @@ else
 
   T.testC(state, "settop 0")
 
-  T.loadlib(state)
+  T.loadlib(state, 1 | 2)   -- load _G and 'package'
 
   assert(T.doremote(state, [[
     coroutine = require'coroutine';
diff --git a/testes/files.lua b/testes/files.lua
index be00bf3f..149e9c76 100644
--- a/testes/files.lua
+++ b/testes/files.lua
@@ -427,12 +427,12 @@ do   -- testing closing file in line iteration
   -- get the to-be-closed variable from a loop
   local function gettoclose (lv)
     lv = lv + 1
-    local stvar = 0   -- to-be-closed is 4th state variable in the loop
+    local stvar = 0   -- to-be-closed is 3th state variable in the loop
     for i = 1, 1000 do
       local n, v = debug.getlocal(lv, i)
       if n == "(for state)" then
         stvar = stvar + 1
-        if stvar == 4 then return v end
+        if stvar == 3 then return v end
       end
     end
   end
diff --git a/testes/main.lua b/testes/main.lua
index 11b14b44..dde72a74 100644
--- a/testes/main.lua
+++ b/testes/main.lua
@@ -137,7 +137,7 @@ RUN('env LUA_INIT= LUA_PATH=x lua %s > %s', prog, out)
 checkout("x\n")
 
 -- test LUA_PATH_version
-RUN('env LUA_INIT= LUA_PATH_5_4=y LUA_PATH=x lua %s > %s', prog, out)
+RUN('env LUA_INIT= LUA_PATH_5_5=y LUA_PATH=x lua %s > %s', prog, out)
 checkout("y\n")
 
 -- test LUA_CPATH
@@ -146,7 +146,7 @@ RUN('env LUA_INIT= LUA_CPATH=xuxu lua %s > %s', prog, out)
 checkout("xuxu\n")
 
 -- test LUA_CPATH_version
-RUN('env LUA_INIT= LUA_CPATH_5_4=yacc LUA_CPATH=x lua %s > %s', prog, out)
+RUN('env LUA_INIT= LUA_CPATH_5_5=yacc LUA_CPATH=x lua %s > %s', prog, out)
 checkout("yacc\n")
 
 -- test LUA_INIT (and its access to 'arg' table)
@@ -156,7 +156,7 @@ checkout("3.2\n")
 
 -- test LUA_INIT_version
 prepfile("print(X)")
-RUN('env LUA_INIT_5_4="X=10" LUA_INIT="X=3" lua %s > %s', prog, out)
+RUN('env LUA_INIT_5_5="X=10" LUA_INIT="X=3" lua %s > %s', prog, out)
 checkout("10\n")
 
 -- test LUA_INIT for files
diff --git a/testes/nextvar.lua b/testes/nextvar.lua
index 02b7dea2..5d8796f7 100644
--- a/testes/nextvar.lua
+++ b/testes/nextvar.lua
@@ -210,9 +210,9 @@ assert(T.querytab(a) == 64)    -- array part has 64 elements
 a[32] = true; a[48] = true;    -- binary search will find these ones
 a[51] = true                   -- binary search will miss this one
 assert(#a == 48)               -- this will set the limit
-assert(select(4, T.querytab(a)) == 48)  -- this is the limit now
+assert(select(3, T.querytab(a)) == 48)  -- this is the limit now
 a[50] = true                   -- this will set a new limit
-assert(select(4, T.querytab(a)) == 50)  -- this is the limit now
+assert(select(3, T.querytab(a)) == 50)  -- this is the limit now
 -- but the size is larger (and still inside the array part)
 assert(#a == 51)
 
@@ -609,10 +609,12 @@ do
   a = 0; for i=1.0, 0.99999, -1 do a=a+1 end; assert(a==1)
 end
 
-do   -- changing the control variable
-  local a
-  a = 0; for i = 1, 10 do a = a + 1; i = "x" end; assert(a == 10)
-  a = 0; for i = 10.0, 1, -1 do a = a + 1; i = "x" end; assert(a == 10)
+do   -- attempt to change the control variable
+  local st, msg = load "for i = 1, 10 do i = 10 end"
+  assert(not st and string.find(msg, "assign to const variable 'i'"))
+
+  local st, msg = load "for v, k in pairs{} do v = 10 end"
+  assert(not st and string.find(msg, "assign to const variable 'v'"))
 end
 
 -- conversion