Can someone tell me why the code below should segfault at the line
indicated?

Also, why does strtok_r() require a **ptrptr and not a *ptr?
(Maybe this is a clue to my problem and misunderstanding of how strtok_r
is used...).

Thanks for any insight.

-Randy

PS: str arg is always guaranteed to point to a valid string < 127 chars


void getNameValuePairFromString(char * str, string & name, string & value)
{
char * buf = (char *) malloc(128);
char * tok = strtok_r(str, " =\n\r", &buf);
if (tok != NULL)
{
name = tok;
tok = strtok_r(NULL, " =\n\r", &buf);
if (tok != NULL)
value = tok;
}
free(buf); // seg fault here !!!
}

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Måns Rullgård wrote:
> RJGraham <null@null.com> writes:
>
> 
[snip][vbcol=seagreen]
>
> strtok_r modifies the value of buf, hence the need for the double
> pointer.  You should save the original value somewhere and pass that
> to free().
>
> 
>
>
Yes, thanks.

I realized that just after posting, which always seems to happen ;)

-Randy

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On Fri, 17 Sep 2004 16:06:25 -0700, RJGraham wrote:

> Can someone tell me why the code below should segfault at the line
> indicated?
>
> Also, why does strtok_r() require a **ptrptr and not a *ptr?
Because how else could it change the pointer you supplied ?

> (Maybe this is a clue to my problem and misunderstanding of how strtok_r
> is used...).
>
> Thanks for any insight.
>
> -Randy
>
> PS: str arg is always guaranteed to point to a valid string < 127 chars
>
>
> void getNameValuePairFromString(char * str, string & name, string & value)
> {
You are changing the buf pointer with the calls to
strtok_r, so when you free it, buf doesn't point to
what you malloced.
Do;

char * buffer = (char *) malloc(128);
char *buf = buffer;
>     char * tok = strtok_r(str, " =\n\r", &buf);
>     if (tok != NULL)
>     {
>        name = tok;
>        tok = strtok_r(NULL, " =\n\r", &buf);
>        if (tok != NULL)
>           value = tok;
>     }

>     free(buf); // seg fault here !!!
And;
free(buffer);
> }
You can probably avoid the malloc/free stuff alltogether, perhaps
just initializing buf to NULL suffices. Never used strtok, and my docs
doesn't do a very good job explaining the _r version though..

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