December 2007 Archives

Function to Function Pointer refactoring

Last week I had some time to work on some C legacy code again and write some unit tests. I've been playing with a refactoring that I've used in the past and now use it all the time when working in C. The refactoring is called "function to function pointer" and is fairly trivial to do and save in legacy code. It gives a lot of flexibility.

The steps are:

  1. Change function prototype to function pointer in the header (just adding (*name)). Make sure it's extern
  2. Rename the function in the .c file to name_impl, or something non conflicting.
  3. At the end of the .c file. Initialize the function pointer with the _impl one.

That's it. Just takes a few seconds and it allows you to dynamically replace the function in your unit tests. It makes unit testing code in C a lot easier. (there are also some variants, but this is the easiest and most basic version)

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This page is an archive of entries from December 2007 listed from newest to oldest.

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