Help me find out what's wrong

I'm an amateur programmer, bare with me:

I am trying to write my own strcat() function and testing it. Here is the code:

Code:

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#include <stdio.h>
#include <string.h>
#include <malloc.h>

int stringcat(char *s, char *t);

int main(void) {   
     
      char *ptr1;
      char *ptr2;
     
      ptr1 = (char *)malloc(20 * sizeof(char));
      ptr2 = (char *)malloc(20 * sizeof(char));   
           
      char message1[] = "Please ";
      char message2[] = "Reconsider\n";
     
      strcpy(ptr1, message1);
      strcpy(ptr2, message2);
     
      stringcat(ptr1, ptr2);
             
      while (*ptr1 != '\0')
            printf("%c", *ptr1++);
           
      free(ptr1);
      free(ptr2);
     
      return 0;
     
}

/* Copies string T to the end of string S */
int stringcat(char *s, char *t)
{
    while (*s++ != '\0')
          ;
    *s--;
   
    while ((*s++ = *t++) != '\0')
          ;
    *s = '\0';
   
    return 0;
}

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I keep getting a parse error around the place where I declare/initialize the arrays (message1 & message2).

Can anybody help me with this? The code looks fine!

Code:

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// PracticeWorkspace.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include<conio.h>

void stringcat(char *s, char *t);

int main(void) {   
     
    char *ptr1 = (char *)malloc(20 * sizeof(char));
        memset(ptr1,'\0',20);
    char *ptr2 = (char *)malloc(20 * sizeof(char));   
           
    char message1[] = "Please ";
    char message2[] = "Reconsider\n";
     
    strcpy(ptr1, message1);
    strcpy(ptr2, message2);
   
    stringcat(ptr1, ptr2);             

        printf("%s",ptr1);
       
        _getch(); 
    free(ptr1);
    free(ptr2);

    return 0;
     
}

/* Copies string T to the end of string S */

void stringcat(char *s, char *t)
{

        while (*s != '\0') s +=1;

        while (*t != '\0')
        {
       
                *s = *t;
                s += 1;
                t += 1;
        }

}

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Reminder to self. I must get used to this new board!

You're problems where here:

Code:

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//no good because it advances the
//pointer, so that free() can not
//free the space properly

while (*ptr1 != '\0')
  printf("%c", *ptr1++);
 
//use printf("%s",ptr1); instead

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Also the other error

Code:

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//should just be s--;           
  *s--;
//and this is not an error
*s = '\0';
//but could have been writen as
*s = *t;
//either way

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What I'm saying here is use your code and just make these changes. It works too.

> I keep getting a parse error around the place where I declare/initialize the arrays (message1 & message2).
Because you're writing C++, and compiling it as C.

C does not allow declarations at statements to be mixed - you must declare all your variables before the first statement in any {} block.

So change them over like this

Code:

---

      char message1[] = "Please ";
      char message2[] = "Reconsider\n";
      ptr1 = (char *)malloc(20 * sizeof(char));
      ptr2 = (char *)malloc(20 * sizeof(char));

---

Quote:

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Originally posted by Salem
> I keep getting a parse error around the place where I declare/initialize the arrays (message1 & message2).
Because you're writing C++, and compiling it as C.

C does not allow declarations at statements to be mixed - you must declare all your variables before the first statement in any {} block.

So change them over like this

Code:

---

      char message1[] = "Please ";
      char message2[] = "Reconsider\n";
      ptr1 = (char *)malloc(20 * sizeof(char));
      ptr2 = (char *)malloc(20 * sizeof(char));

---

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Oh my god, it worked. I never knew that. I always mix them, especially with a for() loop. I usually declare i right before the loop.

Thank you so much for clearing that up.