Re: [patch] Avoid bogus pointer->int cast

[Eric Blake <eblake at redhat dot com>]

On 07/17/2012 11:26 AM, Ralf Corsepius wrote:
> On 07/17/2012 07:21 PM, Ralf Corsepius wrote:
>> Hi,
>>
>> The patch below addresses a (minor) bug in readdir.c. It replaces a
>> (bogus) pointer->int cast with a pointer->intptr_t cast.

Rather than "fixing" the bogus pointer check, why not just nuke that
code altogether?

>  
> +#include <stdint.h>

In other words, no need to drag this in...

>  #include <dirent.h>
>  
>  extern int getdents (int fd, void *dp, int count);
> @@ -75,7 +76,7 @@ _DEFUN(readdir, (dirp),
>        continue;
>      }
>      dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc);

and everything between here...

> -    if ((int)dp & 03) {	/* bogus pointer check */
> +    if ((intptr_t)dp & 03) {	/* bogus pointer check */
>  #ifdef HAVE_DD_LOCK
>        __lock_release_recursive(dirp->dd_lock);
>  #endif
      return NULL;
    }

...and here is just stupid.  POSIX already states that behavior is
undefined if you pass in a bogus pointer; and in a compliant program,
readdir should only ever be called on a valid pointer, making this check
look like nothing more than dead code.  I see no need to bloat the code
with an attempt to gracefully deal with a bogus pointer.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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