foobar.c

/*                                        
 * foobar.c                                     
 * Invoke with:                             
 *      gcc -o foobar -Wall -Wextra -Wno-unused-parameter foobar.c && ./foobar
 */
#include <stdio.h>

#if 1

#define caa_cast_long_keep_sign(v)              \
        ((unsigned long) (v))

#else

#define caa_is_signed_type(type)        ((type) -1 < (type) 0)
#define caa_cast_long_keep_sign(v)              \
(caa_is_signed_type(__typeof__(v)) ?    \
 (unsigned long) (long) (v) :    \
 (unsigned long) (v))

#endif

#define xstr(s) str(s)
#define str(s) #s

#define pr(var)                                                         \
        printf(#var":\t0x%lx %ld\n", caa_cast_long_keep_sign(var), caa_cast_long_keep_sign(var))

#define pru(var)                                                        \
        printf(#var":\t0x%lx %lu\n", caa_cast_long_keep_sign(var), caa_cast_long_keep_sign(var))

int main(int argc, char *argv[])
{
        char c = -128;
        unsigned char uc = ~0;
        long l = __LONG_MAX__;
        unsigned long ul = ~0;
        void *p = NULL;
        void *pp = (void *)0xdeadface;

        pr(c);
        pru(uc);
        pr(l);
        pru(ul);
        pru(p);
        pru(pp);

        return 0;
}