Chapter 5. Pushing the Envelope
In this chapter, you’ll find techniques that you usually won’t need but can, from time to time, be very useful. For example, sometimes it’s useful to extend GNU make’s language by creating new functions in C or even Guile. This chapter shows how to do that and more.
Doing Arithmetic
GNU make has no built-in arithmetic capability. But it is possible to create functions for addition, subtraction, multiplication, and division of integers. You can also create functions for integer comparisons, such as greater than or not equal. These functions are implemented entirely using GNU make’s built-in list and string manipulation functions: $(subst), $(filter), $(filter-out), $(words), $(wordlist), $(call), $(foreach), and
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