我用qmake生成makefile后再进行编译，出现下面错误，请高手指教。
g++ -Wl,-rpath,/usr/local/Trolltech/Qt-4.2.0/lib -o hello -L/usr/local/Trolltech/Qt-4.2.0/lib -lQtGui -L/usr/local/qt/lib -L/usr/X11R6/lib -lpng -lSM -lICE
-lXi -lXrender -lXrandr -lXcursor -lXinerama -lfreetype -lfontconfig -lXext -lX11 -lQtCore -lz -lm -lglib-2.0 -ldl -lpthread
/usr/lib/gcc-lib/i386-redhat-linux/3.2.2/../../../crt1.o(.text+0x18): In function `_start':
../sysdeps/i386/elf/start.S:77: undefined reference to `main'
collect2: ld returned 1 exit status
make: *** [hello] Error 1
