why doesnt this work?

This is a discussion on why doesnt this work? within the C Programming forums, part of the General Programming Boards category; hi, I have these two functions that declare and alter char* arrays - why dosent it work...? ( i know ...

  1. #1
    Registered User
    Join Date
    Jan 2009
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    61

    why doesnt this work?

    hi,

    I have these two functions that declare and alter char* arrays - why dosent it work...? ( i know it dosent i just need some explaning done )

    Code:
    #include <stdio.h>
    
    
    void addchars(char *sa[]){
    
    char *name[10];
    name[0] = "foo";
    
    sprintf(sa, "%s", name[0]);
    
    }
    
    int main() {
    
    char *sa[128];
    
    printf("numbers: %s\n", sa[0]);
    addchars(sa);
    printf("numbers: %s\n", sa[0]);
    
    
    }
    thanks!

  2. #2
    Registered User
    Join Date
    Apr 2008
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    395
    first thing: enable warnings before compiling, this line is wrong:
    Code:
    sprintf(sa, "%s", name[0]);
    and your compiler would have told you if you asked.

    second thing, sa is just an array of pointers, there is no memory allocated for the strings, so sprintf() won't work (segv), replace sprintf() with sa[0]="foo" and you get what you want.

  3. #3
    C++まいる!Cをこわせ!
    Join Date
    Oct 2007
    Posts
    23,001
    You must understand that string literals are really constant: http://cpwiki.sourceforge.net/Common...kes_and_errors
    So when you try to use sprintf, you write into memory where you are not allowed, hence you would get a crash.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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