How to make GCC evaluate functions at compile time?

Question

I am thinking about the following problem: I want to program a microcontroller (let\'s say an AVR mega type) with a program that uses some sort of look-up tables.

Th

Answer 1

First of all, it should go without saying that you should evaluate (probably by experiment) whether this is worth doing. Your lookup table is going to increase your data size and programmer effort, but may or may not provide a runtime speed increase that you need.

If you still want to do it, I don't think the C preprocessor can do it straightforwardly, because it has no facilities for iteration or recursion.

The most robust way to go about this would be to write a program in C or some other language to print out C source for the table, and then include that file in your program using the preprocessor. If you are using a tool like make, you can create a rule to generate the table file and have your .c file depend on that file.

On the other hand, if you are sure you are never going to change this table, you could write a program to generate it once and just paste it in.