Debugging Matlab 2019a does not work in Ubunut

I am trying to debug a mex file in Matlab 2018b or 2019a using gdb under Ubuntu 18.04.

The first error is:

matlab -nojvm -Dgdb

gdb: symbol lookup error: /usr/lib/x86_64-linux-gnu/libpython3.6m.so.1.0: undefined symbol: XML_SetHashSalt

This can be fixed with:

export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libexpatw.so.1

The second error comes as:

matlab -nojvm -Dgdb

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Reading symbols from /usr/local/MATLAB/R2019a/bin/glnxa64/MATLAB...(no debugging symbols found)...done.

(gdb) run

Starting program: /usr/local/MATLAB/R2019a/bin/glnxa64/MATLAB -nojvm

[Thread debugging using libthread_db enabled]

Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

[New Thread 0x7fffe0f80700 (LWP 5096)]

[New Thread 0x7fffdbfff700 (LWP 5097)]

[New Thread 0x7fffdaf21700 (LWP 5098)]

[Thread 0x7fffdbfff700 (LWP 5097) exited]

[New Thread 0x7fffd9915700 (LWP 5104)]

[New Thread 0x7fffd9114700 (LWP 5105)]

[New Thread 0x7fffcb73d700 (LWP 5106)]

Fatal Internal Error: std::exception: Message Catalog MATLAB:branding was not loaded from the file. Please check file location, format or contents

[Thread 0x7fffd9114700 (LWP 5105) exited]

[Thread 0x7fffd9915700 (LWP 5104) exited]

[Thread 0x7fffdaf21700 (LWP 5098) exited]

[Thread 0x7fffe0f80700 (LWP 5096) exited]

[Thread 0x7fffecea9440 (LWP 5091) exited]

[Inferior 1 (process 5091) exited with code 01]

(gdb)

So I cannot start Matlab and get going. Then what?