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Apr 10th, 2007

strpbrk

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hey guyz, i'm trying to search each ar for matching characters in the buff, but I seem to be getting a buffer overflow. Can anyone give me any pointers, any help would be appreciated, this is my code:

C Syntax (Toggle Plain Text)
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
    for (i=0;i<ab;i++)
  { 
 
   pch[i] = strpbrk (ar[i],buff);
    printf ("%c ",pch[i]);
    pch[i] = strpbrk (pch[i],buff);
  }
 
}
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
  
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
    for (i=0;i<ab;i++)
  { 
    
   pch[i] = strpbrk (ar[i],buff);
    printf ("%c ",pch[i]);
    pch[i] = strpbrk (pch[i],buff);
  }
 
}

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rowly

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Apr 10th, 2007

Re: strpbrk

not buffer overflow -- you are not checking that strpbrk() returns a NULL pointer, which it can if the string does not contains the characters.

pch is a 2d array of pointers, so if strpbrk() returns NULL that printf will fail. The format specification in printf() is incorrect too -- should be "%s", not "%c" because pch[i] is a pointer to a string, not a single character.

Ancient Dragon

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Apr 10th, 2007

Re: strpbrk

still getting the same thing...

C Syntax (Toggle Plain Text)
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
   while (pch[i] != NULL)
  {    pch[i] = strpbrk (ar[i], buff);
    printf ("%s " , pch[i]);
    pch[i] = strpbrk (pch[i]+1,buff);
  } }
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
main(int ab, char** ar)
{
 char buff[800];
  int n_chars;
  int i;
  char *pch[300];  
 
  printf("\nplease enter text => ");
  fgets(buff, sizeof(buff), stdin);
   while (pch[i] != NULL)
  {    pch[i] = strpbrk (ar[i], buff);
    printf ("%s " , pch[i]);
    pch[i] = strpbrk (pch[i]+1,buff);
  } }

Last edited by rowly; Apr 10th, 2007 at 2:18 pm. Reason: syntax error

rowly

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Apr 10th, 2007

Re: strpbrk

you have not changed anything. you have to check for NULL AFTER calling strpbrk(), not before. And you also created an infinite loop because the value of i counter is never changed.

>>pch[i]+1
that is wrong -- why are you adding 1 to a pointer value????

Last edited by Ancient Dragon; Apr 10th, 2007 at 3:35 pm.

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