crypt(): Pointer to integer without cast? - c

Question

Aargh! Why is the compiler complaining? Thanks for any help!
% gcc -o mine mine.c -lcrypt
mine.c: In function 'main':
mine.c:19:14: warning: assignment makes pointer from integer without a cast [enabled by default]
%
Code:
#define _X_OPEN_SOURCE
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int main() {
const char key[] = "hello world";
const char salt[]="01";
const int MAXIMUM_HASH_LENGTH = 2 + 11;
int i=0;
char *hash;
long long hashes = 0L;
while (1) {
hash = crypt(key, salt); /* problem with this line... */
if (hash[2] == '0') {
int leading0s = 0;
leading0s++;
for (i=3; i < MAXIMUM_HASH_LENGTH; i++) {
if (hash[i] != '0') break;
leading0s++;
}
printf("Winner: %s has %d leading zeros.\n",
hash, leading0s);
printf("\t--> Hash %lld.\n\n", hashes);
}
if (hashes != 0 && (hashes % 10000) == 0) {
printf("Hash %d: %s\n", hashes, hash);
}
if (hashes== 1000000) break;
hashes++;
}
return 1000;
}

Answer 1

Try changing "#define _X_OPEN_SOURCE" to "#define _XOPEN_SOURCE".

Answer 2

You should normally specify a number for _XOPEN_SOURCE; valid values include:
/*
** Include this file before including system headers. By default, with
** C99 support from the compiler, it requests POSIX 2001 support. With
** C89 support only, it requests POSIX 1997 support. Override the
** default behaviour by setting either _XOPEN_SOURCE or _POSIX_C_SOURCE.
*/
/* _XOPEN_SOURCE 700 is loosely equivalent to _POSIX_C_SOURCE 200809L */
/* _XOPEN_SOURCE 600 is loosely equivalent to _POSIX_C_SOURCE 200112L */
/* _XOPEN_SOURCE 500 is loosely equivalent to _POSIX_C_SOURCE 199506L */
#if !defined(_XOPEN_SOURCE) && !defined(_POSIX_C_SOURCE)
#if __STDC_VERSION__ >= 199901L
#define _XOPEN_SOURCE 600 /* SUS v3, POSIX 1003.1 2004 (POSIX 2001 + Corrigenda) */
#else
#define _XOPEN_SOURCE 500 /* SUS v2, POSIX 1003.1 1997 */
#endif /* __STDC_VERSION__ */
#endif /* !_XOPEN_SOURCE && !_POSIX_C_SOURCE */
You may prefer to use 700 instead of 600; it depends on your platform(s). However, with the correct spelling, you can simply write #define _XOPEN_SOURCE and it will also define the crypt() for you.
You might also care to note that the exit status is limited to an 8-bit value, so returning 1000 from main() is equivalent to returning 1000 % 256. You also need to fix line 34 of your code:
printf("Hash %d: %s\n", hashes, hash);
should be:
printf("Hash %lld: %s\n", hashes, hash);