ProTip: scoped preprocessor definitions

gistfile1.c

#include <stdio.h>

/* #define FOO 33 */

#ifdef FOO
#  pragma push_macro ("FOO")
#  define FOO_WRAPPED
#  undef FOO
#endif

#define FOO 100500

void foo()
{
    printf ("Foo! %d\n", FOO);
}

#ifdef FOO_WRAPPED
#  undef FOO
#  undef FOO_WRAPPED
#  pragma pop_macro ("FOO")
#endif

void bar()
{
#ifdef FOO
    printf ("Bar! %d\n", FOO);
#endif
}

int main (int argc, char *argv[])
{
    foo();
    bar();
    return 0;
}