gethostbyname C function

This is a discussion on gethostbyname C function within the C Programming forums, part of the General Programming Boards category; Hi all, I need to understand this point, so perhaps someone would be able to help. The following code: Code: ...

  1. #1
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    Smile gethostbyname C function

    Hi all,

    I need to understand this point, so perhaps someone would be able to help. The following code:

    Code:
    struct hostent {
       138	        char*    h_name;       ;; official name
       139	        char**   h_aliases;    ;; alias list
       140	        int      h_addrtype;   ;; host address type 
       141	        int      h_length;     ;; length of address 
       142	        char**   h_addr_list;  ;; list of addresses 
       143	     };
    is part of the C Library. Of this, I am interested in knowing
    Code:
    char**   h_aliases;
    points to an array of strings and uses NULL (or 0) as the last element in the list. If you put, -1 in place of NULL, you get a compiler warning. So my question is, why is the compiler willing to accept an array initialization in which the last element is not a string, but an integer?

    Thanks

  2. #2
    int x = *((int *) NULL); Cactus_Hugger's Avatar
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    you get a compiler warning .... why is the compiler willing to accept
    It isn't willing to accept it, so it gives a warning. How/what exactly are you initializing? (And why?) (code snip?) Usually you're reading a hostent, not writing to one...
    Code:
    #include <stdio.h>
    
    int main()
    {
    	char *hosten[] =
    		{ "test", "ing", "this", -1};
    }
    Code:
    $ gcc -o oddprog tomfoolery.c
    tomfoolery.c: In function `main':
    tomfoolery.c:6: warning: initialization makes pointer from integer without a cast
    long time; /* know C? */
    Unprecedented performance: Nothing ever ran this slow before.
    Any sufficiently advanced bug is indistinguishable from a feature.
    Real Programmers confuse Halloween and Christmas, because dec 25 == oct 31.
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    recursion (re - cur' - zhun) n. 1. (see recursion)

  3. #3
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    Question

    Quote Originally Posted by Cactus_Hugger View Post
    It isn't willing to accept it, so it gives a warning. How/what exactly are you initializing? (And why?) (code snip?) Usually you're reading a hostent, not writing to one...
    Code:
    #include <stdio.h>
    
    int main()
    {
    	char *hosten[] =
    		{ "test", "ing", "this", -1};
    }
    Code:
    $ gcc -o oddprog tomfoolery.c
    tomfoolery.c: In function `main':
    tomfoolery.c:6: warning: initialization makes pointer from integer without a cast

    Lets say that we forget -1 for a moment, what I would like to understand is why would char** h_aliases accept an integer as the last argument and not a string?
    Last edited by ladesidude; 07-09-2008 at 09:03 PM.

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