fix issue for using return statement with export.

14 files changed, 125 insertions, 77 deletions

diff --git a/src/lua/lapi.c b/src/lua/lapi.c
index 3e24781..9048245 100644
--- a/src/lua/lapi.c
+++ b/src/lua/lapi.c
@@ -97,8 +97,9 @@ static StkId index2stack (lua_State *L, int idx) {
 
 LUA_API int lua_checkstack (lua_State *L, int n) {
   int res;
-  CallInfo *ci = L->ci;
+  CallInfo *ci;
   lua_lock(L);
+  ci = L->ci;
   api_check(L, n >= 0, "negative 'n'");
   if (L->stack_last - L->top > n)  /* stack large enough? */
     res = 1;  /* yes; check is OK */
@@ -170,10 +171,12 @@ LUA_API int lua_gettop (lua_State *L) {
 
 
 LUA_API void lua_settop (lua_State *L, int idx) {
-  CallInfo *ci = L->ci;
-  StkId func = ci->func;
+  CallInfo *ci;
+  StkId func;
   ptrdiff_t diff;  /* difference for new top */
   lua_lock(L);
+  ci = L->ci;
+  func = ci->func;
   if (idx >= 0) {
     api_check(L, idx <= ci->top - (func + 1), "new top too large");
     diff = ((func + 1) + idx) - L->top;
@@ -376,20 +379,22 @@ LUA_API int lua_toboolean (lua_State *L, int idx) {
 
 
 LUA_API const char *lua_tolstring (lua_State *L, int idx, size_t *len) {
-  TValue *o = index2value(L, idx);
+  TValue *o;
+  lua_lock(L);
+  o = index2value(L, idx);
   if (!ttisstring(o)) {
     if (!cvt2str(o)) {  /* not convertible? */
       if (len != NULL) *len = 0;
+      lua_unlock(L);
       return NULL;
     }
-    lua_lock(L);  /* 'luaO_tostring' may create a new string */
     luaO_tostring(L, o);
     luaC_checkGC(L);
     o = index2value(L, idx);  /* previous call may reallocate the stack */
-    lua_unlock(L);
   }
   if (len != NULL)
     *len = vslen(o);
+  lua_unlock(L);
   return svalue(o);
 }
 
@@ -563,6 +568,7 @@ LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
     while (n--) {
       setobj2n(L, &cl->upvalue[n], s2v(L->top + n));
       /* does not need barrier because closure is white */
+      lua_assert(iswhite(cl));
     }
     setclCvalue(L, s2v(L->top), cl);
     api_incr_top(L);
@@ -624,8 +630,9 @@ static int auxgetstr (lua_State *L, const TValue *t, const char *k) {
 
 
 LUA_API int lua_getglobal (lua_State *L, const char *name) {
-  Table *reg = hvalue(&G(L)->l_registry);
+  Table *reg;
   lua_lock(L);
+  reg = hvalue(&G(L)->l_registry);
   return auxgetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
 }
 
@@ -804,8 +811,9 @@ static void auxsetstr (lua_State *L, const TValue *t, const char *k) {
 
 
 LUA_API void lua_setglobal (lua_State *L, const char *name) {
-  Table *reg = hvalue(&G(L)->l_registry);
+  Table *reg;
   lua_lock(L);  /* unlock done in 'auxsetstr' */
+  reg = hvalue(&G(L)->l_registry);
   auxsetstr(L, luaH_getint(reg, LUA_RIDX_GLOBALS), name);
 }
 
@@ -1093,8 +1101,9 @@ LUA_API int lua_status (lua_State *L) {
 LUA_API int lua_gc (lua_State *L, int what, ...) {
   va_list argp;
   int res = 0;
-  global_State *g = G(L);
+  global_State *g;
   lua_lock(L);
+  g = G(L);
   va_start(argp, what);
   switch (what) {
     case LUA_GCSTOP: {
@@ -1194,9 +1203,15 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
 
 
 LUA_API int lua_error (lua_State *L) {
+  TValue *errobj;
   lua_lock(L);
+  errobj = s2v(L->top - 1);
   api_checknelems(L, 1);
-  luaG_errormsg(L);
+  /* error object is the memory error message? */
+  if (ttisshrstring(errobj) && eqshrstr(tsvalue(errobj), G(L)->memerrmsg))
+    luaM_error(L);  /* raise a memory error */
+  else
+    luaG_errormsg(L);  /* raise a regular error */
   /* code unreachable; will unlock when control actually leaves the kernel */
   return 0;  /* to avoid warnings */
 }
@@ -1238,14 +1253,12 @@ 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 >= 2) {
+  if (n > 0)
     luaV_concat(L, n);
-  }
-  else if (n == 0) {  /* push empty string */
-    setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));
+  else {  /* nothing to concatenate */
+    setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));  /* push empty string */
     api_incr_top(L);
   }
-  /* else n == 1; nothing to do */
   luaC_checkGC(L);
   lua_unlock(L);
 }
diff --git a/src/lua/lauxlib.c b/src/lua/lauxlib.c
index e3d9be3..cbe9ed3 100644
--- a/src/lua/lauxlib.c
+++ b/src/lua/lauxlib.c
@@ -475,8 +475,10 @@ static void *resizebox (lua_State *L, int idx, size_t newsize) {
   lua_Alloc allocf = lua_getallocf(L, &ud);
   UBox *box = (UBox *)lua_touserdata(L, idx);
   void *temp = allocf(ud, box->box, box->bsize, newsize);
-  if (temp == NULL && newsize > 0)  /* allocation error? */
-    luaL_error(L, "not enough memory");
+  if (temp == NULL && newsize > 0) {  /* allocation error? */
+    lua_pushliteral(L, "not enough memory");
+    lua_error(L);  /* raise a memory error */
+  }
   box->box = temp;
   box->bsize = newsize;
   return temp;
diff --git a/src/lua/lcorolib.c b/src/lua/lcorolib.c
index 7d6e585..c165031 100644
--- a/src/lua/lcorolib.c
+++ b/src/lua/lcorolib.c
@@ -73,11 +73,12 @@ static int luaB_coresume (lua_State *L) {
 static int luaB_auxwrap (lua_State *L) {
   lua_State *co = lua_tothread(L, lua_upvalueindex(1));
   int r = auxresume(L, co, lua_gettop(L));
-  if (r < 0) {
+  if (r < 0) {  /* error? */
     int stat = lua_status(co);
-    if (stat != LUA_OK && stat != LUA_YIELD)
-      lua_resetthread(co);  /* close variables in case of errors */
-    if (lua_type(L, -1) == LUA_TSTRING) {  /* error object is a string? */
+    if (stat != LUA_OK && stat != LUA_YIELD)  /* error in the coroutine? */
+      lua_resetthread(co);  /* close its tbc variables */
+    if (stat != LUA_ERRMEM &&  /* not a memory error and ... */
+        lua_type(L, -1) == LUA_TSTRING) {  /* ... error object is a string? */
       luaL_where(L, 1);  /* add extra info, if available */
       lua_insert(L, -2);
       lua_concat(L, 2);
diff --git a/src/lua/ldo.c b/src/lua/ldo.c
index c563b1d..4c976a1 100644
--- a/src/lua/ldo.c
+++ b/src/lua/ldo.c
@@ -245,13 +245,12 @@ static int stackinuse (lua_State *L) {
 
 void luaD_shrinkstack (lua_State *L) {
   int inuse = stackinuse(L);
-  int goodsize = inuse + (inuse / 8) + 2*EXTRA_STACK;
+  int goodsize = inuse + BASIC_STACK_SIZE;
   if (goodsize > LUAI_MAXSTACK)
     goodsize = LUAI_MAXSTACK;  /* respect stack limit */
   /* if thread is currently not handling a stack overflow and its
      good size is smaller than current size, shrink its stack */
-  if (inuse <= (LUAI_MAXSTACK - EXTRA_STACK) &&
-      goodsize < L->stacksize)
+  if (inuse <= (LUAI_MAXSTACK - EXTRA_STACK) && goodsize < L->stacksize)
     luaD_reallocstack(L, goodsize, 0);  /* ok if that fails */
   else  /* don't change stack */
     condmovestack(L,{},{});  /* (change only for debugging) */
@@ -466,13 +465,13 @@ 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);
-      checkstackp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      CallInfo *ci;
+      checkstackGCp(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;
@@ -486,12 +485,13 @@ 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);
+      checkstackGCp(L, fsize, func);
+      L->ci = ci = next_ci(L);
       ci->nresults = nresults;
       ci->u.l.savedpc = p->code;  /* starting point */
       ci->callstatus = 0;
@@ -505,7 +505,7 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       break;
     }
     default: {  /* not a function */
-      checkstackp(L, 1, func);  /* space for metamethod */
+      checkstackGCp(L, 1, func);  /* space for metamethod */
       luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
       goto retry;  /* try again with metamethod */
     }
@@ -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);
@@ -706,9 +706,10 @@ LUA_API int lua_isyieldable (lua_State *L) {
 
 LUA_API int lua_yieldk (lua_State *L, int nresults, lua_KContext ctx,
                         lua_KFunction k) {
-  CallInfo *ci = L->ci;
+  CallInfo *ci;
   luai_userstateyield(L, nresults);
   lua_lock(L);
+  ci = L->ci;
   api_checknelems(L, nresults);
   if (unlikely(!yieldable(L))) {
     if (L != G(L)->mainthread)
diff --git a/src/lua/ldo.h b/src/lua/ldo.h
index 7760f85..6c6cb28 100644
--- a/src/lua/ldo.h
+++ b/src/lua/ldo.h
@@ -17,6 +17,8 @@
 ** Macro to check stack size and grow stack if needed.  Parameters
 ** 'pre'/'pos' allow the macro to preserve a pointer into the
 ** stack across reallocations, doing the work only when needed.
+** It also allows the running of one GC step when the stack is
+** reallocated.
 ** 'condmovestack' is used in heavy tests to force a stack reallocation
 ** at every check.
 */
@@ -35,7 +37,7 @@
 
 
 /* macro to check stack size, preserving 'p' */
-#define checkstackp(L,n,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 */ \
@@ -44,7 +46,7 @@
 
 /* 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' */
diff --git a/src/lua/lgc.c b/src/lua/lgc.c
index f26c921..f7fd7a5 100644
--- a/src/lua/lgc.c
+++ b/src/lua/lgc.c
@@ -1131,16 +1131,14 @@ static void finishgencycle (lua_State *L, global_State *g) {
 
 
 /*
-** Does a young collection. First, mark 'OLD1' objects.  (Only survival
-** and "recent old" lists can contain 'OLD1' objects. New lists cannot
-** contain 'OLD1' objects, at most 'OLD0' objects that were already
-** visited when marked old.) Then does the atomic step. Then,
-** sweep all lists and advance pointers. Finally, finish the collection.
+** Does a young collection. First, mark 'OLD1' objects. Then does the
+** atomic step. Then, sweep all lists and advance pointers. Finally,
+** finish the collection.
 */
 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);
 
diff --git a/src/lua/liolib.c b/src/lua/liolib.c
index 7ac3444..60ab1bf 100644
--- a/src/lua/liolib.c
+++ b/src/lua/liolib.c
@@ -52,6 +52,12 @@ static int l_checkmode (const char *mode) {
 ** =======================================================
 */
 
+#if !defined(l_checkmodep)
+/* By default, Lua accepts only "r" or "w" as mode */
+#define l_checkmodep(m) ((m[0] == 'r' || m[0] == 'w') && m[1] == '\0')
+#endif
+
+
 #if !defined(l_popen)           /* { */
 
 #if defined(LUA_USE_POSIX)      /* { */
@@ -279,6 +285,7 @@ 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, l_checkmodep(mode), 2, "invalid mode");
   p->f = l_popen(L, filename, mode);
   p->closef = &io_pclose;
   return (p->f == NULL) ? luaL_fileresult(L, 0, filename) : 1;
diff --git a/src/lua/llimits.h b/src/lua/llimits.h
index b86d345..48c97f9 100644
--- a/src/lua/llimits.h
+++ b/src/lua/llimits.h
@@ -84,7 +84,15 @@ typedef LUAI_UACNUMBER l_uacNumber;
 typedef LUAI_UACINT l_uacInt;
 
 
-/* internal assertions for in-house debugging */
+/*
+** Internal assertions for in-house debugging
+*/
+#if defined LUAI_ASSERT
+#undef NDEBUG
+#include <assert.h>
+#define lua_assert(c)           assert(c)
+#endif
+
 #if defined(lua_assert)
 #define check_exp(c,e)          (lua_assert(c), (e))
 /* to avoid problems with conditions too long */
diff --git a/src/lua/lmem.c b/src/lua/lmem.c
index 65bfa52..43739bf 100644
--- a/src/lua/lmem.c
+++ b/src/lua/lmem.c
@@ -22,7 +22,7 @@
 #include "lstate.h"
 
 
-#if defined(HARDMEMTESTS)
+#if defined(EMERGENCYGCTESTS)
 /*
 ** First allocation will fail whenever not building initial state
 ** and not shrinking a block. (This fail will trigger 'tryagain' and
diff --git a/src/lua/lobject.c b/src/lua/lobject.c
index b4efae4..f8ea917 100644
--- a/src/lua/lobject.c
+++ b/src/lua/lobject.c
@@ -215,37 +215,42 @@ static lua_Number lua_strx2number (const char *s, char **endptr) {
 /* }====================================================== */
 
 
-/* maximum length of a numeral */
+/* maximum length of a numeral to be converted to a number */
 #if !defined (L_MAXLENNUM)
 #define L_MAXLENNUM     200
 #endif
 
+/*
+** Convert string 's' to a Lua number (put in 'result'). Return NULL on
+** fail or the address of the ending '\0' on success. ('mode' == 'x')
+** means a hexadecimal numeral.
+*/
 static const char *l_str2dloc (const char *s, lua_Number *result, int mode) {
   char *endptr;
   *result = (mode == 'x') ? lua_strx2number(s, &endptr)  /* try to convert */
                           : lua_str2number(s, &endptr);
   if (endptr == s) return NULL;  /* nothing recognized? */
   while (lisspace(cast_uchar(*endptr))) endptr++;  /* skip trailing spaces */
-  return (*endptr == '\0') ? endptr : NULL;  /* OK if no trailing characters */
+  return (*endptr == '\0') ? endptr : NULL;  /* OK iff no trailing chars */
 }
 
 
 /*
-** Convert string 's' to a Lua number (put in 'result'). Return NULL
-** on fail or the address of the ending '\0' on success.
-** 'pmode' points to (and 'mode' contains) special things in the string:
-** - 'x'/'X' means a hexadecimal numeral
-** - 'n'/'N' means 'inf' or 'nan' (which should be rejected)
-** - '.' just optimizes the search for the common case (nothing special)
+** Convert string 's' to a Lua number (put in 'result') handling the
+** current locale.
 ** This function accepts both the current locale or a dot as the radix
 ** mark. If the conversion fails, it may mean number has a dot but
 ** locale accepts something else. In that case, the code copies 's'
 ** to a buffer (because 's' is read-only), changes the dot to the
 ** current locale radix mark, and tries to convert again.
+** The variable 'mode' checks for special characters in the string:
+** - 'n' means 'inf' or 'nan' (which should be rejected)
+** - 'x' means a hexadecimal numeral
+** - '.' just optimizes the search for the common case (no special chars)
 */
 static const char *l_str2d (const char *s, lua_Number *result) {
   const char *endptr;
-  const char *pmode = strpbrk(s, ".xXnN");
+  const char *pmode = strpbrk(s, ".xXnN");  /* look for special chars */
   int mode = pmode ? ltolower(cast_uchar(*pmode)) : 0;
   if (mode == 'n')  /* reject 'inf' and 'nan' */
     return NULL;
@@ -333,8 +338,15 @@ int luaO_utf8esc (char *buff, unsigned long x) {
 }
 
 
-/* maximum length of the conversion of a number to a string */
-#define MAXNUMBER2STR   50
+/*
+** Maximum length of the conversion of a number to a string. Must be
+** enough to accommodate both LUA_INTEGER_FMT and LUA_NUMBER_FMT.
+** (For a long long int, this is 19 digits plus a sign and a final '\0',
+** adding to 21. For a long double, it can go to a sign, 33 digits,
+** the dot, an exponent letter, an exponent sign, 5 exponent digits,
+** and a final '\0', adding to 43.)
+*/
+#define MAXNUMBER2STR   44
 
 
 /*
@@ -375,7 +387,7 @@ void luaO_tostring (lua_State *L, TValue *obj) {
 */
 
 /* size for buffer space used by 'luaO_pushvfstring' */
-#define BUFVFS          400
+#define BUFVFS          200
 
 /* buffer used by 'luaO_pushvfstring' */
 typedef struct BuffFS {
@@ -387,18 +399,16 @@ typedef struct BuffFS {
 
 
 /*
-** Push given string to the stack, as part of the buffer. If the stack
-** is almost full, join all partial strings in the stack into one.
+** Push given string to the stack, as part of the buffer, and
+** join the partial strings in the stack into one.
 */
 static void pushstr (BuffFS *buff, const char *str, size_t l) {
   lua_State *L = buff->L;
   setsvalue2s(L, L->top, luaS_newlstr(L, str, l));
   L->top++;  /* may use one extra slot */
   buff->pushed++;
-  if (buff->pushed > 1 && L->top + 1 >= L->stack_last) {
-    luaV_concat(L, buff->pushed);  /* join all partial results into one */
-    buff->pushed = 1;
-  }
+  luaV_concat(L, buff->pushed);  /* join partial results into one */
+  buff->pushed = 1;
 }
 
 
@@ -521,8 +531,7 @@ const char *luaO_pushvfstring (lua_State *L, const char *fmt, va_list argp) {
   }
   addstr2buff(&buff, fmt, strlen(fmt));  /* rest of 'fmt' */
   clearbuff(&buff);  /* empty buffer into the stack */
-  if (buff.pushed > 1)
-    luaV_concat(L, buff.pushed);  /* join all partial results */
+  lua_assert(buff.pushed == 1);
   return svalue(s2v(L->top - 1));
 }
 
diff --git a/src/lua/lstate.c b/src/lua/lstate.c
index 4434211..28853dc 100644
--- a/src/lua/lstate.c
+++ b/src/lua/lstate.c
@@ -318,9 +318,10 @@ static void close_state (lua_State *L) {
 
 
 LUA_API lua_State *lua_newthread (lua_State *L) {
-  global_State *g = G(L);
+  global_State *g;
   lua_State *L1;
   lua_lock(L);
+  g = G(L);
   luaC_checkGC(L);
   /* create new thread */
   L1 = &cast(LX *, luaM_newobject(L, LUA_TTHREAD, sizeof(LX)))->l;
@@ -395,6 +396,7 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->allgc = obj2gco(L);  /* by now, only object is the main thread */
   L->next = NULL;
   g->Cstacklimit = L->nCcalls = LUAI_MAXCSTACK + CSTACKERR;
+  incnny(L);  /* main thread is always non yieldable */
   g->frealloc = f;
   g->ud = ud;
   g->warnf = NULL;
@@ -436,8 +438,8 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
 
 
 LUA_API void lua_close (lua_State *L) {
-  L = G(L)->mainthread;  /* only the main thread can be closed */
   lua_lock(L);
+  L = G(L)->mainthread;  /* only the main thread can be closed */
   close_state(L);
 }
 
diff --git a/src/lua/ltm.c b/src/lua/ltm.c
index ae60983..4770f96 100644
--- a/src/lua/ltm.c
+++ b/src/lua/ltm.c
@@ -240,7 +240,7 @@ void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
   int actual = cast_int(L->top - ci->func) - 1;  /* number of arguments */
   int nextra = actual - nfixparams;  /* number of extra arguments */
   ci->u.l.nextraargs = nextra;
-  checkstackGC(L, p->maxstacksize + 1);
+  luaD_checkstack(L, p->maxstacksize + 1);
   /* copy function to the top of the stack */
   setobjs2s(L, L->top++, ci->func);
   /* move fixed parameters to the top of the stack */
@@ -259,7 +259,7 @@ 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 */
-    checkstackp(L, nextra, where);  /* ensure stack space */
+    checkstackGCp(L, nextra, where);  /* ensure stack space */
     L->top = where + nextra;  /* next instruction will need top */
   }
   for (i = 0; i < wanted && i < nextra; i++)
diff --git a/src/lua/lundump.c b/src/lua/lundump.c
index 4243678..cb124d6 100644
--- a/src/lua/lundump.c
+++ b/src/lua/lundump.c
@@ -200,13 +200,20 @@ static void loadProtos (LoadState *S, Proto *f) {
 }
 
 
+/*
+** Load the upvalues for a function. The names must be filled first,
+** because the filling of the other fields can raise read errors and
+** the creation of the error message can call an emergency collection;
+** in that case all prototypes must be consistent for the GC.
+*/
 static void loadUpvalues (LoadState *S, Proto *f) {
   int i, n;
   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++)  /* make array valid for GC */
     f->upvalues[i].name = NULL;
+  for (i = 0; i < n; i++) {  /* following calls can raise errors */
     f->upvalues[i].instack = loadByte(S);
     f->upvalues[i].idx = loadByte(S);
     f->upvalues[i].kind = loadByte(S);
diff --git a/src/lua/lvm.c b/src/lua/lvm.c
index e7781db..66d451b 100644
--- a/src/lua/lvm.c
+++ b/src/lua/lvm.c
@@ -634,7 +634,8 @@ static void copy2buff (StkId top, int n, char *buff) {
 ** from 'L->top - total' up to 'L->top - 1'.
 */
 void luaV_concat (lua_State *L, int total) {
-  lua_assert(total >= 2);
+  if (total == 1)
+    return;  /* "all" values already concatenated */
   do {
     StkId top = L->top;
     int n = 2;  /* number of elements handled in this pass (at least 2) */
@@ -840,10 +841,8 @@ void luaV_finishOp (lua_State *L) {
       int a = GETARG_A(inst);      /* first element to concatenate */
       int total = cast_int(top - 1 - (base + a));  /* yet to concatenate */
       setobjs2s(L, top - 2, top);  /* put TM result in proper position */
-      if (total > 1) {  /* are there elements to concat? */
-        L->top = top - 1;  /* top is one after last element (at top-2) */
-        luaV_concat(L, total);  /* concat them (may yield again) */
-      }
+      L->top = top - 1;  /* top is one after last element (at top-2) */
+      luaV_concat(L, total);  /* concat them (may yield again) */
       break;
     }
     default: {
@@ -1102,9 +1101,9 @@ void luaV_finishOp (lua_State *L) {
 /* idem, but without changing the stack */
 #define halfProtectNT(exp)  (savepc(L), (exp))
 
-
+/* 'c' is the limit of live values in the stack */
 #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); }
 
@@ -1635,7 +1634,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         while (!ttisfunction(s2v(ra))) {  /* not a function? */
           luaD_tryfuncTM(L, ra);  /* try '__call' metamethod */
           b++;  /* there is now one extra argument */
-          checkstackp(L, 1, ra);
+          checkstackGCp(L, 1, ra);
         }
         if (!ttisLclosure(s2v(ra))) {  /* C function? */
           luaD_call(L, ra, LUA_MULTRET);  /* call it */
@@ -1792,8 +1791,7 @@ 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 */