ip_tables.h does not compile when using g++

ip_tables.h does not compile when using g++

[Scott Andrew Baillie]

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Hi,

I noticed a discussion on this list in May regarding this problem
but nobody seemed to care.

The file linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h is
included by user space programs as well as the kernel, hence I think
that it should compile using g++.

This patch makes it compile. Patch is also attached.


diff -ur linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h
linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h
--- linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h	Mon Feb 25
19:38:13 2002
+++ linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h	Sat Sep 14
11:11:01 2002
@@ -292,7 +292,7 @@
 static __inline__ struct ipt_entry_target *
 ipt_get_target(struct ipt_entry *e)
 {
-	return (void *)e + e->target_offset;
+	return ((struct ipt_entry_target *)((char *)e + e->target_offset));
 }
 
 /* fn returns 0 to continue iteration */

Regards,

Scott.



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diff -ur linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h
--- linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h	Mon Feb 25 19:38:13 2002
+++ linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h	Sat Sep 14 11:11:01 2002
@@ -292,7 +292,7 @@
 static __inline__ struct ipt_entry_target *
 ipt_get_target(struct ipt_entry *e)
 {
-	return (void *)e + e->target_offset;
+	return ((struct ipt_entry_target *)((char *)e + e->target_offset));
 }
 
 /* fn returns 0 to continue iteration */

Re: ip_tables.h does not compile when using g++

[Harald Welte]

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On Sat, Sep 14, 2002 at 12:07:22PM +0000, Scott Andrew Baillie wrote:
> The file linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h is
> included by user space programs as well as the kernel, hence I think
> that it should compile using g++.

You are right.

> This patch makes it compile. Patch is also attached.
> 
> 
> diff -ur linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h
> linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h
> --- linux-2.4.19/include/linux/netfilter_ipv4/ip_tables.h	Mon Feb 25
> 19:38:13 2002
> +++ linux-2.4.19-new/include/linux/netfilter_ipv4/ip_tables.h	Sat Sep 14
> 11:11:01 2002
> @@ -292,7 +292,7 @@
>  static __inline__ struct ipt_entry_target *
>  ipt_get_target(struct ipt_entry *e)
>  {
> -	return (void *)e + e->target_offset;
> +	return ((struct ipt_entry_target *)((char *)e + e->target_offset));

why does it have to be (char *) ? There are no characters involved, hence
it (in the spirit of this gcc extension) should be (void *).

The typecast to struct ipt_entry_target is correct, however.

Does it compile with 

	return ((struct ipt_entry_target *)((void *)e + e->target_offset));

If yes, I will submit this modified version of  your patch.

> Regards,
> Scott.



-- 
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- Harald Welte / laforge@gnumonks.org               http://www.gnumonks.org/
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Re: ip_tables.h does not compile when using g++

[Scott Andrew Baillie]

Hi Harald,

>
> why does it have to be (char *) ? There are no characters involved,
> hence it (in the spirit of this gcc extension) should be (void *).
>
> The typecast to struct ipt_entry_target is correct, however.
>
> Does it compile with 
>
> return ((struct ipt_entry_target *)((void *)e + e->target_offset));
>
> If yes, I will submit this modified version of  your patch.

No, it does not compile with (void *) at all. Here is the error message
from gcc-3.2 when compiling using g++ :

ip_tables.h: In
   function `ipt_entry_target* ipt_get_target(ipt_entry*)':
ip_tables.h:295: pointer
   of type `void *' used in arithmetic


I agree that the (char *) looks a little confusing but I dont know
what else to use.

Also, just below the function 'ipt_get_target' there is 2 macros
defined that use the same (void *) cast. These casts should also
be patched.

Regards,

Scott.