Thread: Pointers stuff

  1. #1
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    Post Pointers stuff

    getting trouble with this program.
    trying to return a reverse string to main but it doesn't work.
    when I put the function into main it works.
    I think I'm not using the correct way dealing with pointers.
    What am I doing wrong?

    Code:
    #include <stdio.h>#include <stdlib.h>
    #include <string.h>
    char * rev(char * word);
    int main()
    {
           char word1[100];
           char rev1[100];
           printf("Enter a word");
           scanf("\n%s",word1);
           strcpy(rev1,rev(word1));
           printf("\nThe reverse order of this word is: %s",rev1);
           return 0;
    
    
    
    
    }
    char * rev(char * word)
    {
        int len=strlen(word);
    
    
        char reverse[len];
        int j=0;
        for(int i=len-1;i>=0;i--)
        {
               reverse[i]=word[j];
               ++j;
        }
        reverse[len]='\0';
        return reverse;
    }

  2. #2
    and the hat of int overfl Salem's Avatar
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    There are two (or 3) things wrong with your rev function.
    1. Your local reverse array is too short (there is no room for a \0)
    2. Your local array goes out of scope when you return. You don't return arrays, you return only pointers.
    3. Only C99 supports variable length arrays.

    Assuming you want to keep the original string, you need something like this.
    Code:
    char *rev(const char *word, char *reverse) {
      // your existing logic
      return reverse;
    }
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  3. #3
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    Shouldn't this post be in the C section? It's not C++.

  4. #4
    and the hat of int overfl Salem's Avatar
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    Quote Originally Posted by thmm View Post
    Shouldn't this post be in the C section? It's not C++.
    Yes, moved.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.

  5. #5
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    Quote Originally Posted by Salem View Post
    There are two (or 3) things wrong with your rev function.
    1. Your local reverse array is too short (there is no room for a \0)
    2. Your local array goes out of scope when you return. You don't return arrays, you return only pointers.
    3. Only C99 supports variable length arrays.

    Assuming you want to keep the original string, you need something like this.
    Code:
    char *rev(const char *word, char *reverse) {
      // your existing logic
      return reverse;
    }
    thank u for helping -now it works

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