This is a procedure for reading unfamiliar code in C++.
1. Have a goal in mind.
Don’t approach the code without something to do. Approach the code with a plan, and only concentrate on learning the code you need to in order to accomplish that plan. You should never expect to understand the entire codebase.
Keep a notes file, as if you were writing documentation for someone else. More often than not, that someone else will be you, when you try to understand the code again in six months.
Describe the flow of the program for the part of it you are interested in, and note the various data structures. If you don’t know some operation, write down the question, and go answer it.
3. Find the main loop
Depending on what you want to do with the code, you need to find the main loop that executes it. If a bash script calls some binary, go find the
main() for that binary. Walk through
main() until you see the part of the code relevant to your interests. You should only concentrate on that part of the code.
Doxygen is absolutely essential in approaching unfamiliar codebases. Set up some reasonable defaults in the Doxyfile, by changing the setting on the following variables:
HAVE_DOT = YES
CLASS_GRAPH = YES
COLLABORATION_GRAPH = YES
GROUP_GRAPHS = YES
TEMPLATE_RELATIONS = YES
INCLUDE_GRAPH = YES
DISTRIBUTE_GROUP_DOC = YES
EXTRACT_ALL = YES
SOURCE_BROWSER = YES
INLINE_SOURCES = YES
GENERATE_LATEX = NO
- (Feel free to change this if you do want to see latex inside docstrings.)
Generate the html, and open it in a browser. That will let you go through class structures while reading the code, making it easier to understand.
5. Changing the code
Attempt to change a part of the code to do what you want. Mirror the syntax of existing code. Iterate through 2-5 continually.