Re: [Qemu-devel] [5532] Replace uses of strndup (a GNU extension) with Qemu pstrdup

["Blue Swirl" <blauwirbel@gmail.com>]

On 10/25/08, andrzej zaborowski <balrogg@gmail.com> wrote:
> 2008/10/25 Blue Swirl <blauwirbel@gmail.com>:
>  > On 10/25/08, andrzej zaborowski <balrogg@gmail.com> wrote:
>  >> 2008/10/25 Blue Swirl <blauwirbel@gmail.com>:
>  >>  > On 10/25/08, andrzej zaborowski <balrogg@gmail.com> wrote:
>  >>  >> 2008/10/25 Blue Swirl <blauwirbel@gmail.com>:
>  >>  >>
>  >>  >> > Revision: 5532
>  >>  >>  >          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=5532
>  >>  >>  > Author:   blueswir1
>  >>  >>  > Date:     2008-10-25 11:23:27 +0000 (Sat, 25 Oct 2008)
>  >>  >>  >
>  >>  >>  > Log Message:
>  >>  >>  > -----------
>  >>  >>  > Replace uses of strndup (a GNU extension) with Qemu pstrdup
>  >>  >>  >
>  >>  >>  > Modified Paths:
>  >>  >>  > --------------
>  >>  >>  >    trunk/cutils.c
>  >>  >>  >    trunk/hw/bt-hci.c
>  >>  >>  >    trunk/qemu-common.h
>  >>  >>  >
>  >>  >>  > Modified: trunk/cutils.c
>  >>  >>  > ===================================================================
>  >>  >>  > --- trunk/cutils.c      2008-10-25 11:21:28 UTC (rev 5531)
>  >>  >>  > +++ trunk/cutils.c      2008-10-25 11:23:27 UTC (rev 5532)
>  >>  >>  > @@ -50,6 +50,18 @@
>  >>  >>  >     return buf;
>  >>  >>  >  }
>  >>  >>  >
>  >>  >>  > +/* strdup with a limit */
>  >>  >>  > +char *pstrdup(const char *str, size_t buf_size)
>  >>  >>  > +{
>  >>  >>  > +    size_t len;
>  >>  >>  > +    char *buf;
>  >>  >>  > +
>  >>  >>  > +    len = MIN(buf_size, strlen(str));
>  >>  >>  > +    buf = qemu_malloc(len);
>  >>  >>  > +    pstrcpy(buf, len, str);
>  >>  >>  > +    return buf;
>  >>  >>  > +}
>  >>  >>
>  >>  >>
>  >>  >> I think here also pstrcpy will only copy up to buf_size - 1 characters
>  >>  >>  while strndup would copy buf_size chars.
>  >>  >
>  >>  > That is actually safer if we always want the strings to be NUL terminated.
>  >>
>  >>
>  >> strndup also always NUL terminates the string so it's just as safe,
>  >>  the length is just different.
>  >>
>  >>
>  >>  >
>  >>  > But the allocation length is wrong, it should be MIN(buf_size, strlen(str) + 1).
>  >>
>  >>
>  >> By my reading of the manual, it should rather be MIN(buf_size, strlen(str)) + 1.
>  >
>  > But then the length could be incorrect: buf_size + 1.
>
>
> That's what it should be in case lmp_name is 248 chars long.  I think
>  the confusion is because you called the parameter buf_size while
>  strndup calls it n (the number of characters.. not buffer size).

If strlen(lmp_name) >= 248, only first 247 should be copied and the
final character should be NUL, because sizeof(read_local_name_rp.name)
== buf_size == 248.

>  Note that you can use memcpy instead of pstrcpy because the length is
>  known so there's no need for the overhead.

Right.