strtok_r crashing

strtok_r crashing

[Hemant Mohan]

Hi,

I am trying to parse a string using strtok_r (I need reentrant code) as
follows:

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

int main()
{
  char *str = NULL;
  char *temp = NULL;
  char **ptr = NULL;   // Note that this is a char**
  int x = 0;
  int y = 0;

  str = malloc (10*sizeof(char));
  sprintf ( str,"%s", "320x240");
  temp = strtok_r ( str, "Xx", ptr );
  x = atoi(temp);
  temp = strtok_r ( NULL, "Xx", ptr);
  y = atoi(temp);
  printf("x = %d\t y= %d\n", x, y);

 return 0;
}


This code receives a SIGSEGV in strtok_r.

However, if I change the declaration of ptr from char** to char* and change 
the third arguement of strtok_r to  &ptr it works.
That is
char* ptr = NULL;
temp = strtok_r ( str, "Xx" &ptr);

Can anyone please help me know the difference between these two calls
as I think both calls are similar.

Thanks,
Hemant Mohan

-------------------------------------------------------

Re: strtok_r crashing

[Jan-Benedict Glaw]

[-- Attachment #1: Type: text/plain, Size: 852 bytes --]

On Thu, 2002-11-14 18:16:04 +0530, Hemant Mohan <hemantm@pune.tcs.co.in>
wrote in message <OF8E547BE6.AC22B859-ON65256C71.0045BBB6@pune.tcs.co.in>:
> Hi,
> 
> I am trying to parse a string using strtok_r (I need reentrant code) as
> follows:
> 
> #include <string.h>
> #include <stdio.h>
> #include <stdlib.h>
> 
> int main()
> {
>   char *str = NULL;
>   char *temp = NULL;
>   char **ptr = NULL;   // Note that this is a char**

Note that there's no memory allocated for *ptr.

> This code receives a SIGSEGV in strtok_r.

Surely. Accessing random memory.


-- 
   Jan-Benedict Glaw       jbglaw@lug-owl.de    . +49-172-7608481
   "Eine Freie Meinung in  einem Freien Kopf    | Gegen Zensur
    fuer einen Freien Staat voll Freier Bürger" | im Internet!
   Shell Script APT-Proxy: http://lug-owl.de/~jbglaw/software/ap2/

[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: strtok_r crashing

[Hemant Mohan]

Does that mean thaat I need to malloc the ptr before passing it to the 
strtok_r.  If so then what sould be the size ?? should it be the size of the 
str (strlen(str))??

On Thursday 14 November 2002 06:20 pm, 
linux-c-programming-owner@vger.kernel.org wrote:
> On Thu, 2002-11-14 18:16:04 +0530, Hemant Mohan <hemantm@pune.tcs.co.in>
>
> wrote in message <OF8E547BE6.AC22B859-ON65256C71.0045BBB6@pune.tcs.co.in>:
> > Hi,
> >
> > I am trying to parse a string using strtok_r (I need reentrant code) as
> > follows:
> >
> > #include <string.h>
> > #include <stdio.h>
> > #include <stdlib.h>
> >
> > int main()
> > {
> >   char *str = NULL;
> >   char *temp = NULL;
> >   char **ptr = NULL;   // Note that this is a char**
>
> Note that there's no memory allocated for *ptr.
>
> > This code receives a SIGSEGV in strtok_r.
>
> Surely. Accessing random memory.

Re: strtok_r crashing

[Glynn Clements]

Hemant Mohan wrote:

> > > I am trying to parse a string using strtok_r (I need reentrant code) as
> > > follows:
> > >
> > > #include <string.h>
> > > #include <stdio.h>
> > > #include <stdlib.h>
> > >
> > > int main()
> > > {
> > >   char *str = NULL;
> > >   char *temp = NULL;
> > >   char **ptr = NULL;   // Note that this is a char**
> >
> > Note that there's no memory allocated for *ptr.
> >
> > > This code receives a SIGSEGV in strtok_r.
> >
> > Surely. Accessing random memory.
> 
> Does that mean thaat I need to malloc the ptr before passing it to the 
> strtok_r.  If so then what sould be the size ?? should it be the size of the 
> str (strlen(str))??

No, you don't need to use malloc(). You just need to ensure that the
third argument points to valid memory, e.g.

	char *temp;
	char *ptr; /* this is NOT a char ** */
	...
	temp = strtok_r ( str, "Xx", &ptr );
	x = atoi(temp);
	temp = strtok_r ( NULL, "Xx", &ptr);
	y = atoi(temp);

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: strtok_r crashing

[Hemant Mohan]

OK, I think I got the point.

Thanks a lot
Hemant
On Friday 15 November 2002 11:56 am, Glynn Clements wrote:
> Hemant Mohan wrote:
> > > > I am trying to parse a string using strtok_r (I need reentrant code)
>
> as
>
> > > > follows:
> > > >
> > > > #include <string.h>
> > > > #include <stdio.h>
> > > > #include <stdlib.h>
> > > >
> > > > int main()
> > > > {
> > > >   char *str = NULL;
> > > >   char *temp = NULL;
> > > >   char **ptr = NULL;   // Note that this is a char**
> > >
> > > Note that there's no memory allocated for *ptr.
> > >
> > > > This code receives a SIGSEGV in strtok_r.
> > >
> > > Surely. Accessing random memory.
> >
> > Does that mean thaat I need to malloc the ptr before passing it to the
> > strtok_r.  If so then what sould be the size ?? should it be the size of
>
> the
>
> > str (strlen(str))??
>
> No, you don't need to use malloc(). You just need to ensure that the
> third argument points to valid memory, e.g.
>
>      char *temp;
>      char *ptr; /* this is NOT a char ** */
>      ...
>      temp = strtok_r ( str, "Xx", &ptr );
>      x = atoi(temp);
>      temp = strtok_r ( NULL, "Xx", &ptr);
>      y = atoi(temp);