passing by reference... my darkest enemy
actual reason below:
In your case (without reference) the compiler generates a temporary object (int) for the first argument of your MyApplication constructor. You pass this temporary int to QApplication’s constructor (with int reference), which saves the address of this reference. Once your MyApplication constructor is done the temporary int is destroyed but QApplication still has its address.
/*
** $Id: lopcodes.c,v 1.37.1.1 2007/12/27 13:02:25 roberto Exp $
** See Copyright Notice in lua.h
*/
#define lopcodes_c
#define LUA_CORE
#include "lopcodes.h"
/* ORDER OP */
const char *const luaP_opnames[NUM_OPCODES+1] = {
"MOVE",
"LOADK",
"LOADBOOL",
"LOADNIL",
"GETUPVAL",
"GETGLOBAL",
"GETTABLE",
"SETGLOBAL",
"SETUPVAL",
"SETTABLE",
"NEWTABLE",
"SELF",
"ADD",
"SUB",
"MUL",
"DIV",
"MOD",
"POW",
"UNM",
"NOT",
"LEN",
"CONCAT",
"JMP",
"EQ",
"LT",
"LE",
"TEST",
"TESTSET",
"CALL",
"TAILCALL",
"RETURN",
"FORLOOP",
"FORPREP",
"TFORLOOP",
"SETLIST",
"CLOSE",
"CLOSURE",
"VARARG",
NULL
};
#define opmode(t,a,b,c,m) (((t)<<7) | ((a)<<6) | ((b)<<4) | ((c)<<2) | (m))
const lu_byte luaP_opmodes[NUM_OPCODES] = {
/* T A B C mode opcode */
opmode(0, 1, OpArgR, OpArgN, iABC) /* OP_MOVE */
,opmode(0, 1, OpArgK, OpArgN, iABx) /* OP_LOADK */
,opmode(0, 1, OpArgU, OpArgU, iABC) /* OP_LOADBOOL */
,opmode(0, 1, OpArgR, OpArgN, iABC) /* OP_LOADNIL */
,opmode(0, 1, OpArgU, OpArgN, iABC) /* OP_GETUPVAL */
,opmode(0, 1, OpArgK, OpArgN, iABx) /* OP_GETGLOBAL */
,opmode(0, 1, OpArgR, OpArgK, iABC) /* OP_GETTABLE */
,opmode(0, 0, OpArgK, OpArgN, iABx) /* OP_SETGLOBAL */
,opmode(0, 0, OpArgU, OpArgN, iABC) /* OP_SETUPVAL */
,opmode(0, 0, OpArgK, OpArgK, iABC) /* OP_SETTABLE */
,opmode(0, 1, OpArgU, OpArgU, iABC) /* OP_NEWTABLE */
,opmode(0, 1, OpArgR, OpArgK, iABC) /* OP_SELF */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_ADD */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_SUB */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_MUL */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_DIV */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_MOD */
,opmode(0, 1, OpArgK, OpArgK, iABC) /* OP_POW */
,opmode(0, 1, OpArgR, OpArgN, iABC) /* OP_UNM */
,opmode(0, 1, OpArgR, OpArgN, iABC) /* OP_NOT */
,opmode(0, 1, OpArgR, OpArgN, iABC) /* OP_LEN */
,opmode(0, 1, OpArgR, OpArgR, iABC) /* OP_CONCAT */
,opmode(0, 0, OpArgR, OpArgN, iAsBx) /* OP_JMP */
,opmode(1, 0, OpArgK, OpArgK, iABC) /* OP_EQ */
,opmode(1, 0, OpArgK, OpArgK, iABC) /* OP_LT */
,opmode(1, 0, OpArgK, OpArgK, iABC) /* OP_LE */
,opmode(1, 1, OpArgR, OpArgU, iABC) /* OP_TEST */
,opmode(1, 1, OpArgR, OpArgU, iABC) /* OP_TESTSET */
,opmode(0, 1, OpArgU, OpArgU, iABC) /* OP_CALL */
,opmode(0, 1, OpArgU, OpArgU, iABC) /* OP_TAILCALL */
,opmode(0, 0, OpArgU, OpArgN, iABC) /* OP_RETURN */
,opmode(0, 1, OpArgR, OpArgN, iAsBx) /* OP_FORLOOP */
,opmode(0, 1, OpArgR, OpArgN, iAsBx) /* OP_FORPREP */
,opmode(1, 0, OpArgN, OpArgU, iABC) /* OP_TFORLOOP */
,opmode(0, 0, OpArgU, OpArgU, iABC) /* OP_SETLIST */
,opmode(0, 0, OpArgN, OpArgN, iABC) /* OP_CLOSE */
,opmode(0, 1, OpArgU, OpArgN, iABx) /* OP_CLOSURE */
,opmode(0, 1, OpArgU, OpArgN, iABC) /* OP_VARARG */
};