The Mozilla code base is very old. It dates back to before many of the common features of C++ today existed. As a result, people need to get used to a lot of arcane patterns and idioms that don’t really feel great for those used to more modern code bases. This has been especially difficult for new contributors as it increases the barrier to entry for them by adding to the list of new things that they need to learn before they can be effective working on the Mozilla code.
This pattern bothered a lot of people, and Michael Wu fixed the first notable example of such arcane pattern: converting the usage of the type PRBool to bool. PRBool is a typedef to int which was used all around our code base instead of the C++ bool type. I then followed the train by converting instances of PR_TRUE and PR_FALSE in our code base to true and false. Aryeh Gregor then stepped up to convert our null value, nsnull, into the C++11 nullptr. And I recently switched our usages of NSPR numeric types (such as PRInt16/PRUint32) to the stdint.h numeric types (int16_t, uint32_t).
This has been a long and hard road, and we should continue to do more of this in the future. While this type of work may not seem that interesting as it’s not improving any of the user/web developer facing features, I believe it’s very important to the continuous growth of the Mozilla project, as it makes the code more modern and pleasant to read, and it makes the live of people contributing to the Mozilla code base for the first time much easier.
If you have ideas on more of this kind of cleanup, or are interested in helping with this effort, please contact me!