A somewhat tongue-in-cheek title, but this page lists a few very important rules you should always keep in mind when creating makefiles. Following these rules will allow your makefiles to be both pithy and beautiful. And they will make maintaining and modifying them, and thus your entire life, a much more pleasant experience.
- Use GNU
Don’t hassle with writing portable makefiles, use a portable
- Every non-
.PHONYrule must update a file with the exact name of its target.
Make sure every command script touches the file “
../$@“, or “
$(notdir $@)“, but exactly
$@. That way you and GNU
- Life is simplest if the targets are built in the current working directory.
VPATHto locate the sources from the objects directory, not to locate the objects from the sources directory.
- Follow the Principle of Least Repetition.
Try to never write a filename more than once. Do this through a combination of make variables, pattern rules, automatic variables, and GNU
- Every non-continued line that starts with a TAB is part of a command script–and vice versa.
If a non-continued line does not begin with a TAB character, it is never part of a command script: it is always interpreted as
makefilesyntax. If a non-continued line does begin with a TAB character, it is always part of a command script: it is never interpreted as
makefilesyntax. Note this is not strictly true but you are best off pretending it is always true.
Continued lines are always of the same type as their predecessor, regardless of what characters they start with.
- Don’t use directories as normal prerequisites.
It’s virtually never correct to use a directory as a normal prerequisite for a target. GNU
maketreats directories as any other file and rebuilds the target if the modification time of the directory has changed. However, modification times of directories change whenever a file is added, removed, or renamed in that directory… this is almost never what you want. It is useful to list directories as order-only prerequisites, however.
Yes, that’s all of them… so far. It’s not that that’s all I have to say on the subject, but coming up with points which are both truly fundamental and expressible in a succinct rule format, ain’t easy.
Let me know if you have suggestions.