diff --git a/ldo.c b/ldo.c
index c30cde76..2a0017ca 100644
--- a/ldo.c
+++ b/ldo.c
@@ -299,17 +299,13 @@ static int stackinuse (lua_State *L) {
 */
 void luaD_shrinkstack (lua_State *L) {
   int inuse = stackinuse(L);
-  int nsize = inuse * 2;  /* proposed new size */
-  int max = inuse * 3;  /* maximum "reasonable" size */
-  if (max > LUAI_MAXSTACK) {
-    max = LUAI_MAXSTACK;  /* respect stack limit */
-    if (nsize > LUAI_MAXSTACK)
-      nsize = LUAI_MAXSTACK;
-  }
+  int max = (inuse > LUAI_MAXSTACK / 3) ? LUAI_MAXSTACK : inuse * 3;
   /* if thread is currently not handling a stack overflow and its
      size is larger than maximum "reasonable" size, shrink it */
-  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max)
+  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max) {
+    int nsize = (inuse > LUAI_MAXSTACK / 2) ? LUAI_MAXSTACK : inuse * 2;
     luaD_reallocstack(L, nsize, 0);  /* ok if that fails */
+  }
   else  /* don't change stack */
     condmovestack(L,{},{});  /* (change only for debugging) */
   luaE_shrinkCI(L);  /* shrink CI list */
@@ -629,7 +625,7 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
 ** check the stack before doing anything else. 'luaD_precall' already
 ** does that.
 */
-l_sinline void ccall (lua_State *L, StkId func, int nResults, int inc) {
+l_sinline void ccall (lua_State *L, StkId func, int nResults, l_uint32 inc) {
   CallInfo *ci;
   L->nCcalls += inc;
   if (l_unlikely(getCcalls(L) >= LUAI_MAXCCALLS)) {
diff --git a/lopcodes.h b/lopcodes.h
index 7c274515..4c551453 100644
--- a/lopcodes.h
+++ b/lopcodes.h
@@ -21,7 +21,7 @@ iABC          C(8)     |      B(8)     |k|     A(8)      |   Op(7)     |
 iABx                Bx(17)               |     A(8)      |   Op(7)     |
 iAsBx              sBx (signed)(17)      |     A(8)      |   Op(7)     |
 iAx                           Ax(25)                     |   Op(7)     |
-isJ                           sJ(25)                     |   Op(7)     |
+isJ                           sJ (signed)(25)            |   Op(7)     |
 
   A signed argument is represented in excess K: the represented value is
   the written unsigned value minus K, where K is half the maximum for the
diff --git a/ltable.c b/ltable.c
index cc7993e0..3c690c5f 100644
--- a/ltable.c
+++ b/ltable.c
@@ -257,9 +257,11 @@ LUAI_FUNC unsigned int luaH_realasize (const Table *t) {
     size |= (size >> 2);
     size |= (size >> 4);
     size |= (size >> 8);
+#if (UINT_MAX >> 14) > 3  /* unsigned int has more than 16 bits */
     size |= (size >> 16);
 #if (UINT_MAX >> 30) > 3
     size |= (size >> 32);  /* unsigned int has more than 32 bits */
+#endif
 #endif
     size++;
     lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);