gdb不能工作了

我用的是FC6 用gdb调试一个非常简单的程序，出现了
GNU gdb Red Hat Linux (6.5-8.fc6rh)
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This GDB was configured as "i386-redhat-linux-gnu"...“/home/feng/Ccode/main.c": not in executable format: 不可识别的文件格式
请问这是为什么呀！  请教高手的指点！！

make sure that you are debugging the executable file.