Please Enable full debug logging: Settings->Debugger->Common->Full (Debug) log. There you see exactly what is going on, and why the debugger fails.
Plugin question:
So do I need to copy my complete source code and put it inside plugin section in codeblocks_svn_code?
No. Simply open both projects in one workspace (by opening simply both projects). But the settings of the projects have to be ok, and i think there is your problem...
As Tim suggested you should try to build and debug a contrib plugin first.
1) For this open a contrib plugin project from /PATHTOCODEBLOCKS/src/plugins/contrib/ProjectOptionsManipulator/ProjectOptionsManipulator.cbp .
2) Then open /PATHTOCODEBLOCKS/src/CodeBlocks.cbp .
3) Activate again the ProjectOptionsManipulator.cbp by double click int the Management pane. This project should now be marked as active (The name is bold).
4) Check if the correct "default" target is selected in the toolbar near the build button
5) In the Management panel browse to Codeblocks/Source/src/app.cpp (BUT DON'T ACTIVATE THE PROJECT) and go to line 610. Set a breakpoint there
6) Set a breakpoint of interest in the ProjectOptionsManipulator source
7) Now hit the debugger button
It should now halt first at src/app.cpp:610
9) Hit continue if the debugger stops until you hit the desired breakpoint
If this works you can look into the project settings, how the project is set up and compare it wit your settings. Then you should find the error why your plugin is not debugging correctly. If you have found the error can you please post it here?
[EDIT:] I am not sure but probably you have to build codeblocks with debugging symbols enabled. You do this by Settings->Global Variables->cb_release_type and add "-g" in the "base" field. Then you have to rebuild Codeblocks by hitting Build->Rebuild