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.
/***************************************************************************/
/* */
/* otvalid.h */
/* */
/* OpenType table validation (specification only). */
/* */
/* Copyright 2004, 2008 by */
/* David Turner, Robert Wilhelm, and Werner Lemberg. */
/* */
/* This file is part of the FreeType project, and may only be used, */
/* modified, and distributed under the terms of the FreeType project */
/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
/* this file you indicate that you have read the license and */
/* understand and accept it fully. */
/* */
/***************************************************************************/
#ifndef __OTVALID_H__
#define __OTVALID_H__
#include <ft2build.h>
#include FT_FREETYPE_H
#include "otverror.h" /* must come before FT_INTERNAL_VALIDATE_H */
#include FT_INTERNAL_VALIDATE_H
#include FT_INTERNAL_STREAM_H
FT_BEGIN_HEADER
FT_LOCAL( void )
otv_BASE_validate( FT_Bytes table,
FT_Validator valid );
/* GSUB and GPOS tables should already be validated; */
/* if missing, set corresponding argument to 0 */
FT_LOCAL( void )
otv_GDEF_validate( FT_Bytes table,
FT_Bytes gsub,
FT_Bytes gpos,
FT_UInt glyph_count,
FT_Validator valid );
FT_LOCAL( void )
otv_GPOS_validate( FT_Bytes table,
FT_UInt glyph_count,
FT_Validator valid );
FT_LOCAL( void )
otv_GSUB_validate( FT_Bytes table,
FT_UInt glyph_count,
FT_Validator valid );
/* GSUB and GPOS tables should already be validated; */
/* if missing, set corresponding argument to 0 */
FT_LOCAL( void )
otv_JSTF_validate( FT_Bytes table,
FT_Bytes gsub,
FT_Bytes gpos,
FT_UInt glyph_count,
FT_Validator valid );
FT_LOCAL( void )
otv_MATH_validate( FT_Bytes table,
FT_UInt glyph_count,
FT_Validator ftvalid );
FT_END_HEADER
#endif /* __OTVALID_H__ */
/* END */