armdem.exe -output option not working

HI,

I'm using armdem.exe to demangle the c++ variable name but I cannot use the --output,-o option aince I always get the error: Cannot open output file: `null`.

I'm using Arm 5.1.8 compiler. My command line is: 

armdem.exe -o=test1.txt myfile.txt

Could you tell me how to use the output option please.

Thanks.

David.