The most useful user-made C-macros (in GCC, also C99)? [closed]

Answer 1

If you need to define data multiple times in different contexts, macros can help you avoid have to relist the same thing multiple times.

For example, lets say you want to define an enum of colors and an enum-to-string function, rather then list all the colors twice, you could create a file of the colors (colors.def):

c(red)
c(blue)
c(green)
c(yellow)
c(brown)

Now you can in your c file you can define your enum and your string conversion function:

enum {
#define c(color) color,
# include "colors.def"
#undef c
};

const char *
color_to_string(enum color col)
{
    static const char *colors[] = {
#define c(color) #color,
# include "colors.def"
#undef c
    };
    return (colors[col]);
};