Bugs happen. Identifying and fixing them is part of the development process. There are many different techniques for finding and characterizing program defects, including static and dynamic analysis, code review, tracing, profiling, and interactive debugging. I will look at tracers and profilers in the next chapter, but here I want to concentrate on the traditional approach of watching code execution through a debugger, in our case, the GNU debugger, GDB. GDB is a powerful and flexible tool. You can use it to debug applications, examine the postmortem files (core files) that are created after a program crash, and even step through kernel code.
In this chapter, I will show you how to use GDB to debug applications, how to look at core files and how to debug kernel code, in all cases, emphasizing the aspects that are relevant for embedded Linux.
GDB is a source-level debugger for the compiled languages, primarily C and C++, although there is also support for a variety of other languages such as Go and Objective. You should read the notes for the version of GDB you are using to find out the current status of support for the various languages. The project website is http://www.gnu.org/software/gdb and contains a lot of useful information, including the GDB manual.
Out of the box, GDB has a command-line user interface which some people find off-putting although, in reality, it is easy to use with a little practice. If command-line interfaces are not to your liking, there are a lot of front-end user interfaces to GDB and I will describe three of them later.