In linux, how does one debug a project that contains more than N files?

In linux, how does one debug a project that contains more than N files? -- Linux general technology-Linux technology and application information. For details, refer to the following section. I am a newbie. I recently studied the Jabberd stuff and want to make some modifications to the code. So the question is:
The source file of jabberd contains n Multiple folders, and each file # contains various complex relationships. How can I use gdb to debug this ambitious project?

In linux, what tools can be used to debug large projects that contain multiple files?

Gcc-g XXXX-o XXX must be used to debug files in gdb, but this is usually the case for large engineering files, for example, A folder contains folders A and B (B is not in A), and folder a contains. c and. h. The folder B contains B. c and B. h, but. in h # include "B/B. h "...... how can I debug a lot of such relationships? Is there any tool? Do you want to modify Makefile?

Thank you for your guidance ~~~~~