Not able to set gdb correctly in netbeans though following instructions properly

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C++

C

debugger

GNU

I am trying to set gdb so that I can debug C/C++ programs in Netbeans.
I have MacOSX 10.13.6.

I have followed exactly the same steps given in :

First I created a certificate named gdb-cert and imported it in the System Keychain, then finally restarted the system, etc.

debugging - Netbeans "Resolve missing debugger command" C++ - Stack Overflow[^]


I also followed the steps given here:

BuildingOnDarwin - GDB Wiki[^]

When I type codesign -s gdb-cert /usr/local/bin/gdb in terminal it says that /usr/local/bin/gdb is already signed

However when I try to debug my C file it still gives the error :
Unable to find Mach task portfor process id-1248 (os/kern) failure (0x5).\n (please see gdb is codesigned - see taskgated(8))

In tool collection there are 2 options : CLang and GNU. I have chosen GNU and set the path of Debugger Commander for GNU as : /usr/local/bin/gdb as given by command: which gdb

What could be the real problem in this ?

Please help.

What I have tried:

I have spent 3 hours in figuring out the problem. Still no clue.