Subject: Re: ip_tables.h can't be used in C++ programs.

From: Ben Greear <[email-masked]>
Date: Fri, 20 Aug 2010 16:42:59 -0700

On 08/20/2010 04:17 PM, Ben Hutchings wrote:
> On Fri, 2010-08-20 at 11:54 -0700, Ben Greear wrote:
>> This method returns void* but is defined to return
>> a pointer to struct ipt_entry_target.
>>
>> This will not compile under g++ (or, I'm unable to figure out
>> how to make it work w/out editing the header file).
>>
>> Any reason this shouldn't be changed to:
>>
>>    return (struct ipt_entry_target*)e + e->target_offset;
>
> Because that multiplies the offset by sizeof(struct ipt_entry_target)!
>
>> /* Helper functions */
>> static __inline__ struct ipt_entry_target *
>> ipt_get_target(struct ipt_entry *e)
>> {
>>           return (void *)e + e->target_offset;
>> }
>
> For extra unportability, this is relying on the gcc extension for void
> pointer arithmetic.  Try something like:
>
> 	return (struct ipt_entry_target *)((char *)e + e->target_offset);

That compiles fine for me, would be great to get something like
that upstream!

Take it easy,
Ben

-- 
Ben Greear <[email-masked]>
Candela Technologies Inc  http://www.candelatech.com