fitting a StackValue structure into 32 bytes (for 64-bit machines)

lobject.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.h,v 2.127 2017/11/03 12:12:30 roberto Exp roberto $
+** $Id: lobject.h,v 2.128 2017/11/03 17:22:54 roberto Exp roberto $
 ** Type definitions for Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -314,26 +314,27 @@ typedef union StackValue {
   struct {
     TValuefields;
     lu_byte callstatus_;
-    short nresults;  /* expected number of results from this function */
-    unsigned short previous;  /* difference to previous 'func' */
-    unsigned short framesize;  /* stack space available for this function */
+    char nresults;  /* expected number of results from this function */
     union {
-      unsigned short funcidx;  /* called-function index */
-      unsigned short nyield;  /* number of values yielded */
+      unsigned char funcidx;  /* called-function index */
+      unsigned char nyield;  /* number of values yielded */
     } u2;
+    unsigned short previous;  /* difference to previous 'func' */
+    unsigned short framesize;  /* stack space available for this function */
     union {
       struct {  /* only for Lua functions */
         const Instruction *savedpc;
       } l;
       struct {  /* only for C functions */
         lua_KFunction k;  /* continuation in case of yields */
-        ptrdiff_t old_errfunc;
-        lua_KContext ctx;  /* context info. in case of yields */
+        int old_errfunc;
+        int ctx;  /* context info. in case of yields */
       } c;
     } u;
   } stkci;
 } StackValue;
 
+
 #define callstatus(ar)	((ar)->stkci.callstatus_)
 
 /* top of a function (first element after its frame) */