GDB Code Size Analysis

This small script discovers approximately how much code runs to support a particular function call. Using the GDB Python interface, it disassembles interesting functions and records their size.

Getting Started

1. Edit ~/.gdbinit and insert the code from /gdbinit. Change the path on line 6 as necessary.

2. Debug your program under GDB and set a breakpoint in the function you're instrumenting.

3. In the GDB console, do:

   python function_until("fname", "~/filename")

   where fname is the function upon which to stop (I recommend using the caller of the function with the breakpoint). The second argument is the location where the results will be stored for later analysis.

4. Run count.py on the file you created in the previous step.

Why would I use this?

I wrote this script to compute the size of the code loaded by a running process, in order to compute the approximate cache pressure simply due to executing code. This number is surprisingly large, especially in well-architected C++ programs with polymorphism, constructors, and smart pointers.

Acknowledgements

This entire idea was lifted from disussion with alexras, and his gdb-thread-names[https://github.com/alexras/gdb-thread-names].