C中的crypt（）函数不起作用

Question

The following is my file named crack.c:

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

void execute(char *alpha)
{
    char *beta = crypt(alpha);
    printf("%s", beta);
}

int main(int argc, string argv[]){

        ....

        execute(argv[1]);
        else{
            printf("You submitted %d command line arguments.  That's an issue.  You need to submit exactly one.", argc);
            return 1;
        }
}

The following is what I type into the command line:

jharvard@appliance (~/Dropbox/hacker2): clang -o crack -lcrypt crack.c

The following is what the command line spits back out at me:

crack.c:8:19: warning: implicit declaration of function 'crypt' is
invalid in
      C99 [-Wimplicit-function-declaration]
    string beta = crypt(alpha);
                  ^ crack.c:8:12: warning: incompatible integer to pointer conversion initializing
      'string' (aka 'char *') with an expression of type 'int'
      [-Wint-conversion]
    string beta = crypt(alpha);
           ^      ~~~~~~~~~~~~ 2 warnings generated.

Anyone know what's going on?

Answer 1

I had the same problem, and I realized that changing the header

#define _XOPEN_SOURCE
#include <unistd.h>

by

#define _GNU_SOURCE
#include <crypt.h>

makes disapear the error in compilation time

Answer 2

The function signature of crypt is:

char * crypt (const char *key, const char *salt)

It seems that you forgot one parameter! So your line:

string beta = crypt(alpha);

Should be something like that:

string beta = crypt(alpha, salt);

Answer 3

Make sure you have the define and include for crypt as the very first lines at the top of your file before any other includes.

#define _XOPEN_SOURCE
#include <unistd.h>