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.
# Find the Lua library
#
IF(WIN32)
SET(LUA_DEFAULT lua.dll)
ELSE(WIN32)
IF(APPLE)
SET(LUA_DEFAULT lua)
ELSE(APPLE)
#locate the system's lua library
FIND_LIBRARY(LUA_DEFAULT NAMES lua51 lua5.1 lua-5.1 lua PATHS /lib /usr/lib /usr/local/lib /usr/pkg/lib)
IF(${LUA_DEFAULT} MATCHES "LUA_DEFAULT-NOTFOUND")
#UNSET(LUA_DEFAULT)
MESSAGE(FATAL_ERROR "Couldn't find Lua 5.1 library!")
ENDIF()
#remove the path (fpc doesn't like it - why?)
GET_FILENAME_COMPONENT(LUA_DEFAULT ${LUA_DEFAULT} NAME)
ENDIF(APPLE)
ENDIF(WIN32)
SET(LUA_LIBRARY ${LUA_DEFAULT} CACHE STRING "Lua library to link to; file name without path only!")
#UNSET(LUA_DEFAULT)