Better variable exploring when debugging C++ code with Eclipse/CDT

Well, gdb don't natively support STL containers. You can't say this is incorrect, since it will expose the inner workings of the STL objects, but most of the time it is not what we want, right?

If you're using gdb 7.0 you can take advantage of the pretty printers. This website http://sourceware.org/gdb/wiki/STLSupport has a pretty simple tutorial on how to set them. I copied below the part that interests you:

1. Check-out the latest Python libstdc++ printers to a place on your machine. In a local directory, do:

       svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python
   

2. Add the following to your ~/.gdbinit. The path needs to match where the python module above was checked-out. So if checked out to: /home/maude/gdb_printers/, the path would be as written in the example:

       python
       import sys
       sys.path.insert(0, '/home/maude/gdb_printers/python')
       from libstdcxx.v6.printers import register_libstdcxx_printers
       register_libstdcxx_printers (None)
       end
   

The path should be the only element that needs to be adjusted in the example above. Once loaded, STL classes that the printers support should printed in a more human-readable format. To print the classes in the old style, use the /r (raw) switch in the print command (i.e., print /r foo). This will print the classes as if the Python pretty-printers were not loaded.

Since you're using eclipse cdt, don't forget to point your debug configuration to your .gdbinit file. When creating a new Debug Configuration, go to the Debugger tab and put the path to the .gdbinit file in the "GDB command file" field.

I hope that helps!

You need a version of GDB capable of using python to pretty print structures. I know at least on windows using mingw that this is not provided in the default install.

Pretty Printers are python modules which tell gdb how to display a given structure. You can write your own, but there are already printers for STL available for download.

To Get Pretty Printers working on Windows (instructions should be similiar for other OS's):

Prerequisites

• Make sure you have you have Python 2.7 installed and in the system path.

  http://www.python.org/download/

• Make sure MinGW-get is installed

  http://sourceforge.net/projects/mingw/files/Installer/mingw-get-inst/

• Make sure you have an SVN client are installed

Installation:

• Open a command Shell and type:

  mingw-get install gdb-python
  

• When its finished cd to a local directory and install the printers by typing:

  svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python
  

• Open the .gdbinit (create it in a text editor if need be) and type the following replaceing "C:/directory" with the folder that you checked the printers into.

  Python
  import sys
  sys.path.insert(0, 'C:/directory')
  from libstdcxx.v6.printers import register_libstdcxx_printers
  register_libstdcxx_printers (None)
  end
  

Eclipse Setup

• Go To Windows > Preferences > C/C++ > Debug > GDB
• Where it Says GDB Debugger put the path to the python enabled GDB it will most likely be in the mingw /bin folder with a name like gdb-python27.exe
• Where it says GDB Command File put the path to the .gdb init file you made earlier.

That's it, debug like normal, the stl structures should be much easier to read.

In debug view in variables list expand vector:

"vector_name" -> std::_Vector_base<"datatype"> -> _M_impl

then right click on _M_start and select "Display as array...", type its length and then click OK. Now you can expand each item of your vector.