--- a/src/lgc.c
+++ b/src/lgc.c
@@ -856,6 +856,8 @@ static void GCTM (lua_State *L) {
     if (unlikely(status != LUA_OK)) {  /* error while running __gc? */
       luaE_warnerror(L, "__gc metamethod");
       L->top--;  /* pops error object */
+      if (isLua(L->ci))
+        L->oldpc = L->ci->u.l.savedpc;  /* update 'oldpc' */
     }
   }
 }
@@ -1140,7 +1140,7 @@ static void finishgencycle (lua_State *L, global_State *g) {
 static void youngcollection (lua_State *L, global_State *g) {
   GCObject **psurvival;  /* to point to first non-dead survival object */
   lua_assert(g->gcstate == GCSpropagate);
-  markold(g, g->survival, g->reallyold);
+  markold(g, g->allgc, g->reallyold);
   markold(g, g->finobj, g->finobjrold);
   atomic(L);

--- a/src/ldo.c
+++ b/src/ldo.c
@@ -466,13 +466,13 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       f = fvalue(s2v(func));
      Cfunc: {
       int n;  /* number of returns */
-      CallInfo *ci = next_ci(L);
+      CallInfo *ci;
       checkstackp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      L->ci = ci = next_ci(L);
       ci->nresults = nresults;
       ci->callstatus = CIST_C;
       ci->top = L->top + LUA_MINSTACK;
       ci->func = func;
-      L->ci = ci;
       lua_assert(ci->top <= L->stack_last);
       if (L->hookmask & LUA_MASKCALL) {
         int narg = cast_int(L->top - func) - 1;
@@ -486,18 +486,18 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       break;
     }
     case LUA_VLCL: {  /* Lua function */
-      CallInfo *ci = next_ci(L);
+      CallInfo *ci;
       Proto *p = clLvalue(s2v(func))->p;
       int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
       int nfixparams = p->numparams;
       int fsize = p->maxstacksize;  /* frame size */
       checkstackp(L, fsize, func);
+      L->ci = ci = next_ci(L);
       ci->nresults = nresults;
       ci->u.l.savedpc = p->code;  /* starting point */
       ci->callstatus = 0;
       ci->top = func + 1 + fsize;
       ci->func = func;
-      L->ci = ci;
       for (; narg < nfixparams; narg++)
         setnilvalue(s2v(L->top++));  /* complete missing arguments */
       lua_assert(ci->top <= L->stack_last);
@@ -674,7 +674,7 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
   if (from == NULL)
     L->nCcalls = CSTACKTHREAD;
   else  /* correct 'nCcalls' for this thread */
-    L->nCcalls = getCcalls(from) + from->nci - L->nci - CSTACKCF;
+    L->nCcalls = getCcalls(from) - L->nci - CSTACKCF;
   if (L->nCcalls <= CSTACKERR)
     return resume_error(L, "C stack overflow", nargs);
   luai_userstateresume(L, nargs);
--- a/src/lundump.c
+++ b/src/lundump.c
@@ -205,8 +205,9 @@ static void loadUpvalues (LoadState *S, Proto *f) {
   n = loadInt(S);
   f->upvalues = luaM_newvectorchecked(S->L, n, Upvaldesc);
   f->sizeupvalues = n;
-  for (i = 0; i < n; i++) {
+  for (i = 0; i < n; i++)
     f->upvalues[i].name = NULL;
+  for (i = 0; i < n; i++) {
     f->upvalues[i].instack = loadByte(S);
     f->upvalues[i].idx = loadByte(S);
     f->upvalues[i].kind = loadByte(S);
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -1104,7 +1104,7 @@ void luaV_finishOp (lua_State *L) {
 
 
 #define checkGC(L,c)  \
-	{ luaC_condGC(L, L->top = (c),  /* limit of live values */ \
+	{ luaC_condGC(L, (savepc(L), L->top = (c)), \
                          updatetrap(ci)); \
            luai_threadyield(L); }
 
@@ -1792,8 +1792,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_VARARGPREP) {
-        luaT_adjustvarargs(L, GETARG_A(i), ci, cl->p);
-        updatetrap(ci);
+        ProtectNT(luaT_adjustvarargs(L, GETARG_A(i), ci, cl->p));
         if (trap) {
           luaD_hookcall(L, ci);
           L->oldpc = pc + 1;  /* next opcode will be seen as a "new" line */
--- a/src/liolib.c
+++ b/src/liolib.c
@@ -279,6 +279,8 @@ static int io_popen (lua_State *L) {
   const char *filename = luaL_checkstring(L, 1);
   const char *mode = luaL_optstring(L, 2, "r");
   LStream *p = newprefile(L);
+  luaL_argcheck(L, ((mode[0] == 'r' || mode[0] == 'w') && mode[1] == '\0'),
+                   2, "invalid mode");
   p->f = l_popen(L, filename, mode);
   p->closef = &io_pclose;
   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
   
--- a/src/ldo.h
+++ b/src/ldo.h
@@ -44,7 +44,7 @@
 
 /* macro to check stack size and GC */
 #define checkstackGC(L,fsize)  \
-	luaD_checkstackaux(L, (fsize), (void)0, luaC_checkGC(L))
+	luaD_checkstackaux(L, (fsize), luaC_checkGC(L), (void)0)
 
 
 /* type of protected functions, to be ran by 'runprotected' */