I get a linker error whenever I attempt to call the crypt
or fcrypt functions in a program I compile with gcc.  the
result is something like the following:

/tmp/cca070171.o: In function `main':
/tmp/cca070171.o(.text+0xe): undefined reference to `crypt'

Here is the program that give that error:

#define _XOPEN_SOURCE
#include <unistd.h>
#include <stdio.h>

void main(void) {
    printf("%d\n", crypt("password", "Na"));
}

This doesn't occur under RedHat 4.2 or other systems not
using GLibc.