Using GDB with Eigen C++ library

Question

I am using the Eigen C++ library downloadable from http://eigen.tuxfamily.org/. This is a C++ library for easier handling of Matrices and Arrays. I use g++ compiler and gdb for debugging. However, I found that I am unable to print the content of a Matrix (provided by Eigen) while using gdb.

Susumu

Answer 1

You have to install a gdb extension that you can find in eigen/debug/gdb/.

The comment at the beginning of the file explains how to install it.

Vociferous

Is there something similar for lldb on mac os x? – Hypogastrium

I'm not aware of lldb script yet, but it should be difficult to adapt the gdb one to lldb. – Vociferous

link in the answer is dead – Ape

Can you explain how to install this python file? – Profit

It's explained in the file itself! – Vociferous

I have installed it but it's unclear to me how to use it. Could you provide any info on that? I'm using the eclipse debugger btw – Calcariferous

Answer 2

One trick you can use is the .data() member, it gives you a pointer to the raw array that contains the data. With that you can print it in GDB like so:

print *X.data()@Length_X

where X is the eigen variable and Length_X is the product of its rows and columns.

Sunbonnet

Answer 3

There is a github project specifically for adding eigen printing support to GDB.

It appears to be based on the code linked in this answer.

Brad