[libmnl PATCH] include: libmnl.h: Add explicit casts to macros for C++

[libmnl PATCH] include: libmnl.h: Add explicit casts to macros for C++

[Phil Sutter]

C++ does not like implicit casts of void pointers, make them explicit
there. After adjusting similar cases in example source files, these are
the only needed header adjustments needed to compile them with g++.

Reported-by: Yaron Shragai <yshragai.firmware@gmail.com>
Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1156
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 include/libmnl/libmnl.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/libmnl/libmnl.h b/include/libmnl/libmnl.h
index 9c032807097f7..2c18e50e6026d 100644
--- a/include/libmnl/libmnl.h
+++ b/include/libmnl/libmnl.h
@@ -146,12 +146,12 @@ extern bool mnl_attr_ok(const struct nlattr *attr, int len);
 extern struct nlattr *mnl_attr_next(const struct nlattr *attr);
 
 #define mnl_attr_for_each(attr, nlh, offset) \
-	for ((attr) = mnl_nlmsg_get_payload_offset((nlh), (offset)); \
+	for ((attr) = (struct nlattr *)mnl_nlmsg_get_payload_offset((nlh), (offset)); \
 	     mnl_attr_ok((attr), (char *)mnl_nlmsg_get_payload_tail(nlh) - (char *)(attr)); \
 	     (attr) = mnl_attr_next(attr))
 
 #define mnl_attr_for_each_nested(attr, nest) \
-	for ((attr) = mnl_attr_get_payload(nest); \
+	for ((attr) = (struct nlattr *)mnl_attr_get_payload(nest); \
 	     mnl_attr_ok((attr), (char *)mnl_attr_get_payload(nest) + mnl_attr_get_payload_len(nest) - (char *)(attr)); \
 	     (attr) = mnl_attr_next(attr))
 
-- 
2.54.0

Re: [libmnl PATCH] include: libmnl.h: Add explicit casts to macros for C++

[Florian Westphal]

Phil Sutter <phil@nwl.cc> wrote:
> C++ does not like implicit casts of void pointers, make them explicit
> there. After adjusting similar cases in example source files, these are
> the only needed header adjustments needed to compile them with g++.

Reviewed-by: Florian Westphal <fw@strlen.de>

Re: [libmnl PATCH] include: libmnl.h: Add explicit casts to macros for C++

[Phil Sutter]

On Wed, Nov 11, 2026 at 07:27:35PM +0100, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > C++ does not like implicit casts of void pointers, make them explicit
> > there. After adjusting similar cases in example source files, these are
> > the only needed header adjustments needed to compile them with g++.
> 
> Reviewed-by: Florian Westphal <fw@strlen.de>

Applied after dropping the redundant "needed" up there. Thanks for your
review!