The printf("%s %s", foo(), foo()) problem is unusual for crypt() --- but it isn't for other functions that return points to global static memory, inet_ntoa() in particular (you often want to print both source and destination addresses). To get around this, I used to have a preloaded inet_ntoa that alternated between two global static buffers. :)

Our codebase has quite a few functions like inet_ntoa():

    /* returns ptr. to internal static storage */
    const char *type_to_str(const Type *type);

    /* Explicit buffer argument */
    char msg_buf1[256], msg_buf2[256], msg_buf3[256], ..., msg_buf16[256];
    char *type_to_str(char *buf_to_use, size_t buf_size, const Type *type)

    #include <stdio.h>
    
    struct foo {
        int      bar;   
    };  
    
    #define FOO_TO_STR_SIZE 256
    
    #define foo_to_str(foo) \
        foo_to_str_((char [FOO_TO_STR_SIZE]){ 0 }, FOO_TO_STR_SIZE, (foo))

    /* Implementation detail */  
    __attribute__((nonnull))
    static char *foo_to_str_(char *buf_to_use, size_t size,
        const struct foo *foo)
    {   
        (void)snprintf(buf_to_use, size, "%d", foo->bar);
    
        return buf_to_use;
    }
    
    int main(void)
    {
        const struct foo foo = {
            .bar = 42
        },               foo2 = {
            .bar = 43
        };
        printf("%s %s\n", foo_to_str(&foo),
            foo_to_str(&foo2));
    
        return 0;
    }   

The NetBSD man page for inet_ntoa lists "The string returned by inet_ntoa() resides in a static memory area" in the BUGS section, Linux is not so forward about it.

  The string is returned in a statically allocated buffer, which subsequent calls will overwrite.

[1] - http://dir.gmane.org/gmane.comp.security.phc

  string password_hash ( string $password , integer $algo [, array $options ] )
  boolean password_verify ( string $password , string $hash )
  boolean password_needs_rehash ( string $hash , integer $algo [, array $options ] )

For NIS, you'd need to ensure that every machine that touches passwords via NIS is configured to use the same algorithm when users change passwords. On Solaris, just configure CRYPT_* in /etc/security/policy.conf the same on every machine. (See the policy.conf man page — in short, you want to change the default algorithm to 1 [or whatever] and set __unix__ to be deprecated.) On Linux and *BSD, how you do it depends on the distro/version.

Fun fact about changing passwords in NIS: When a yppasswd client contacts rpc.yppasswdd to change a user's password, the user's new password is sent crypt()ed, but the user's old password is sent in the clear.

OpenBSD implemented bcrypt more than 17 years ago http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/crypt/...