#define 只是字符替换

可以使用

#define MAX 100

int
main (int argc, char *argv[])
{
    printf("MAX is %d\n", MAX);
    return ;
}

gcc -E filename.c -o output.c

来看看

output.c:

#  "./def.c"
#  "<built-in>"
#  "<command-line>"
#  "./def.c"

int
main (int argc, char *argv[])
{
   printf("MAX is %d\n", );
   return ;
}