diff --git a/ldo.c b/ldo.c
index c156a40e..c984dd09 100644
--- a/ldo.c
+++ b/ldo.c
@@ -1,5 +1,5 @@
 /*
-** $Id: ldo.c,v 2.45 2007/03/27 14:11:38 roberto Exp roberto $
+** $Id: ldo.c,v 2.46 2008/01/18 22:36:50 roberto Exp roberto $
 ** Stack and Call structure of Lua
 ** See Copyright Notice in lua.h
 */
@@ -193,6 +193,7 @@ void luaD_callhook (lua_State *L, int event, int line) {
       ar.i_ci = cast_int(L->ci - L->base_ci);
     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
     L->ci->top = L->top + LUA_MINSTACK;
+    L->ci->status |= 1;  /* this level is running a hook */
     lua_assert(L->ci->top <= L->stack_last);
     L->allowhook = 0;  /* cannot call hooks inside a hook */
     lua_unlock(L);
@@ -202,6 +203,7 @@ void luaD_callhook (lua_State *L, int event, int line) {
     L->allowhook = 1;
     L->ci->top = restorestack(L, ci_top);
     L->top = restorestack(L, top);
+    L->ci->status &= ~1;  /* this level is not running a hook anymore */
   }
 }
 
@@ -264,6 +266,9 @@ static StkId tryfuncTM (lua_State *L, StkId func) {
    (condhardstacktests(luaD_reallocCI(L, L->size_ci)), ++L->ci))
 
 
+/*
+** returns true if function has been executed (C function)
+*/
 int luaD_precall (lua_State *L, StkId func, int nresults) {
   LClosure *cl;
   ptrdiff_t funcr;
@@ -292,6 +297,7 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
     lua_assert(ci->top <= L->stack_last);
     L->savedpc = p->code;  /* starting point */
     ci->tailcalls = 0;
+    ci->status = 0;
     ci->nresults = nresults;
     for (st = L->top; st < ci->top; st++)
       setnilvalue(st);
@@ -301,7 +307,7 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
       luaD_callhook(L, LUA_HOOKCALL, -1);
       L->savedpc--;  /* correct 'pc' */
     }
-    return PCRLUA;
+    return 0;
   }
   else {  /* if is a C function, call it */
     CallInfo *ci;
@@ -318,12 +324,8 @@ int luaD_precall (lua_State *L, StkId func, int nresults) {
     lua_unlock(L);
     n = (*curr_func(L)->c.f)(L);  /* do the actual call */
     lua_lock(L);
-    if (n < 0)  /* yielding? */
-      return PCRYIELD;
-    else {
-      luaD_poscall(L, L->top - n);
-      return PCRC;
-    }
+    luaD_poscall(L, L->top - n);
+    return 1;
   }
 }
 
@@ -378,7 +380,7 @@ void luaD_call (lua_State *L, StkId func, int nResults) {
     else if (g->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
       luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
   }
-  if (luaD_precall(L, func, nResults) == PCRLUA)  /* is a Lua function? */
+  if (!luaD_precall(L, func, nResults))  /* is a Lua function? */
     luaV_execute(L, 1);  /* call it */
   g->nCcalls--;
   luaC_checkGC(L);
@@ -390,8 +392,8 @@ static void resume (lua_State *L, void *ud) {
   CallInfo *ci = L->ci;
   if (L->status == LUA_OK) {  /* start coroutine? */
     lua_assert(ci == L->base_ci && firstArg > L->base);
-    if (luaD_precall(L, firstArg - 1, LUA_MULTRET) != PCRLUA)
-      return;
+    if (luaD_precall(L, firstArg - 1, LUA_MULTRET))  /* C function? */
+      return;  /* done */
   }
   else {  /* resuming from previous yield */
     lua_assert(L->status == LUA_YIELD);
@@ -434,14 +436,14 @@ LUA_API int lua_resume (lua_State *L, int nargs) {
       return resume_error(L, "C stack overflow");
   L->baseCcalls = ++G(L)->nCcalls;
   status = luaD_rawrunprotected(L, resume, L->top - nargs);
-  if (status != LUA_OK) {  /* error? */
+  if (status != LUA_OK && status != LUA_YIELD) {  /* error? */
     L->status = cast_byte(status);  /* mark thread as `dead' */
     luaD_seterrorobj(L, status, L->top);
     L->ci->top = L->top;
   }
   else {
     lua_assert(L->baseCcalls == G(L)->nCcalls);
-    status = L->status;
+    lua_assert(status == L->status);
   }
   --G(L)->nCcalls;
   L->baseCcalls = 0;
@@ -457,8 +459,11 @@ LUA_API int lua_yield (lua_State *L, int nresults) {
     luaG_runerror(L, "attempt to yield across metamethod/C-call boundary");
   L->base = L->top - nresults;  /* protect stack slots below */
   L->status = LUA_YIELD;
+  if (!isLua(L->ci))  /* not inside a hook? */
+    luaD_throw(L, LUA_YIELD);
+  lua_assert(L->ci->status & 1);  /* must be inside a hook */
   lua_unlock(L);
-  return -1;
+  return 0;  /* otherwise, return to 'luaD_callhook' */
 }
 
 
diff --git a/ldo.h b/ldo.h
index c8d0f872..ad86a09c 100644
--- a/ldo.h
+++ b/ldo.h
@@ -1,5 +1,5 @@
 /*
-** $Id: ldo.h,v 2.8 2006/07/11 15:53:29 roberto Exp roberto $
+** $Id: ldo.h,v 2.9 2008/07/03 14:24:36 roberto Exp roberto $
 ** Stack and Call structure of Lua
 ** See Copyright Notice in lua.h
 */
@@ -28,12 +28,6 @@
 #define restoreci(L,n)		((CallInfo *)((char *)L->base_ci + (n)))
 
 
-/* results from luaD_precall */
-#define PCRLUA		0	/* initiated a call to a Lua function */
-#define PCRC		1	/* did a call to a C function */
-#define PCRYIELD	2	/* C funtion yielded */
-
-
 /* type of protected functions, to be ran by `runprotected' */
 typedef void (*Pfunc) (lua_State *L, void *ud);
 
diff --git a/lvm.c b/lvm.c
index b295d5eb..c499913a 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1,5 +1,5 @@
 /*
-** $Id: lvm.c,v 2.73 2007/09/10 17:59:32 roberto Exp roberto $
+** $Id: lvm.c,v 2.74 2008/04/02 16:16:06 roberto Exp roberto $
 ** Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -415,7 +415,7 @@ void luaV_execute (lua_State *L, int nexeccalls) {
       traceexec(L);
       if (L->status == LUA_YIELD) {  /* did hook yield? */
         L->savedpc--;  /* undo increment */
-        return;
+        luaD_throw(L, LUA_YIELD);
       }
       base = L->base;
     }
@@ -595,51 +595,40 @@ void luaV_execute (lua_State *L, int nexeccalls) {
         int b = GETARG_B(i);
         int nresults = GETARG_C(i) - 1;
         if (b != 0) L->top = ra+b;  /* else previous instruction set top */
-        switch (luaD_precall(L, ra, nresults)) {
-          case PCRLUA: {
-            nexeccalls++;
-            goto reentry;  /* restart luaV_execute over new Lua function */
-          }
-          case PCRC: {
-            /* it was a C function (`precall' called it); adjust results */
-            if (nresults >= 0) L->top = L->ci->top;
-            base = L->base;
-            continue;
-          }
-          default: {
-            return;  /* yield */
-          }
+        if (luaD_precall(L, ra, nresults)) {  /* C function? */
+          if (nresults >= 0) L->top = L->ci->top;  /* adjust results */
+          base = L->base;
+          continue;
+        }
+        else {  /* Lua function */
+          nexeccalls++;
+          goto reentry;  /* restart luaV_execute over new Lua function */
         }
       }
       case OP_TAILCALL: {
         int b = GETARG_B(i);
         if (b != 0) L->top = ra+b;  /* else previous instruction set top */
         lua_assert(GETARG_C(i) - 1 == LUA_MULTRET);
-        switch (luaD_precall(L, ra, LUA_MULTRET)) {
-          case PCRLUA: {
-            /* tail call: put new frame in place of previous one */
-            CallInfo *ci = L->ci - 1;  /* previous frame */
-            int aux;
-            StkId func = ci->func;
-            StkId pfunc = (ci+1)->func;  /* previous function index */
-            if (L->openupval) luaF_close(L, ci->base);
-            L->base = ci->base = ci->func + ((ci+1)->base - pfunc);
-            for (aux = 0; pfunc+aux < L->top; aux++)  /* move frame down */
-              setobjs2s(L, func+aux, pfunc+aux);
-            ci->top = L->top = func+aux;  /* correct top */
-            lua_assert(L->top == L->base + clvalue(func)->l.p->maxstacksize);
-            ci->savedpc = L->savedpc;
-            ci->tailcalls++;  /* one more call lost */
-            L->ci--;  /* remove new frame */
-            goto reentry;
-          }
-          case PCRC: {  /* it was a C function (`precall' called it) */
-            base = L->base;
-            continue;
-          }
-          default: {
-            return;  /* yield */
-          }
+        if (luaD_precall(L, ra, LUA_MULTRET)) {  /* C function? */
+          base = L->base;
+          continue;
+        }
+        else {
+          /* tail call: put new frame in place of previous one */
+          CallInfo *ci = L->ci - 1;  /* previous frame */
+          int aux;
+          StkId func = ci->func;
+          StkId pfunc = (ci+1)->func;  /* previous function index */
+          if (L->openupval) luaF_close(L, ci->base);
+          L->base = ci->base = ci->func + ((ci+1)->base - pfunc);
+          for (aux = 0; pfunc+aux < L->top; aux++)  /* move frame down */
+            setobjs2s(L, func+aux, pfunc+aux);
+          ci->top = L->top = func+aux;  /* correct top */
+          lua_assert(L->top == L->base + clvalue(func)->l.p->maxstacksize);
+          ci->savedpc = L->savedpc;
+          ci->tailcalls++;  /* one more call lost */
+          L->ci--;  /* remove new frame */
+          goto reentry;
         }
       }
       case OP_RETURN: {