Re: [PATCH 2/2] tests/vhost-user-bridge.c: Fix const qualifier build errors with recent glibc

[Yodel Eldar <yodel.eldar@yodel.dev>]

On 13/12/2025 00:59, Cédric Le Goater wrote:
> On 12/13/25 01:17, Yodel Eldar wrote:
>>
>> On 12/12/2025 17:33, Yodel Eldar wrote:
>>> Hi, Cédric!
>>>
>>> On 10/12/2025 12:13, Cédric Le Goater wrote:
>>>> A recent change in glibc 2.42.9000 [1] changes the return type of
>>>> strstr() and other string functions to be 'const char *' when the
>>>> input is a 'const char *'. This breaks the build in :
>>>>
>>>> ../tests/vhost-user-bridge.c: In function ‘vubr_parse_host_port’:
>>>> ../tests/vhost-user-bridge.c:749:15: error: initialization discards 
>>>> ‘const’ qualifier from pointer target type [-Werror=discarded- 
>>>> qualifiers]
>>>>    749 |     char *p = strchr(buf, ':');
>>>>        |               ^~~~~~
>>>>
>>>> Fix this by using the glib g_strsplit() routine instead of strdup().
>>>>
>>>> [1] https://sourceware.org/git/? 
>>>> p=glibc.git;a=commit;h=cd748a63ab1a7ae846175c532a3daab341c62690
>>>>
>>>> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
>>>> Signed-off-by: Cédric Le Goater <clg@redhat.com>
>>>> ---
>>>>   tests/vhost-user-bridge.c | 10 ++++------
>>>>   1 file changed, 4 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
>>>> index 
>>>> a5c711b1de8e9c164dd1614f4329b8e3c05d0402..ce4c3426d3938a0b54195f3e95bb1f1c3c4ae823 100644
>>>> --- a/tests/vhost-user-bridge.c
>>>> +++ b/tests/vhost-user-bridge.c
>>>> @@ -746,14 +746,12 @@ vubr_run(VubrDev *dev)
>>>>   static int
>>>>   vubr_parse_host_port(const char **host, const char **port, const 
>>>> char *buf)
>>>>   {
>>>> -    char *p = strchr(buf, ':');
>>>> -
>>>> -    if (!p) {
>>>> +    g_auto(GStrv) tokens = g_strsplit(buf, ":", 2);
>>>> +    if (!tokens[0] || !tokens[1]) {
>>>>           return -1;
>>>>       }
>>>> -    *p = '\0';
>>>> -    *host = strdup(buf);
>>>> -    *port = strdup(p + 1);
>>>> +    *host = g_steal_pointer(&tokens[0]);
>>>> +    *port = g_steal_pointer(&tokens[1]);
>>>>       return 0;
>>>>   }
>>>
>>> Thanks for addressing this before the glibc change is widely propagated
>>> among distros.
>>>
>>> Acked-by: Yodel Eldar <yodel.eldar@yodel.dev>
>>> Tested-by: Yodel Eldar <yodel.eldar@yodel.dev>
>>>
>>> For testing, I built and installed glibc (76 commits ahead of cd748a63a)
>>> in an x86_64 Linux container and built vhost-user-bridge on top of that.
>>> Ran it with:
>>>
>>> ./build/tests/vhost-user-bridge -H
>>>
>>> qemu-system-x86_64 \
>>>      -enable-kvm -m 4G \
>>>      -object memory-backend-ram,id=mem0,size=4G,share=on \
>>>      -numa node,memdev=mem0 -mem-prealloc \
>>>      -chardev socket,id=char0,path=/tmp/vubr.sock \
>>>      -netdev type=vhost-user,id=net0,chardev=char0,vhostforce=on \
>>>      -device virtio-net-pci,netdev=net0 \
>>>      -drive file=linux.qcow2
>>>
>>> and visually inspected the logged traffic.
>>>
>>> Thanks,
>>> Yodel
>>>
>>
>> P.S. To build vhost-user-bridge, I had to modify util/log.c as in
>> the PULL submission "<20251209200537.84097-9-philmd@linaro.org>".
>>
>> For completion, the commands used:
>>
>> ../configure --enable-tools --enable-vhost-user --disable-system \
>>    --disable-user
>>
>> ninja tests/vhost-user-bridge
>>
>> Yodel
>>
> 
> 
> Thanks Yodel,
> 
> My plan is to send a small PR as soon as QEMU 10.2 is out and ask
> Michael T. to include the changes in the stable branches.
> 
> C.
> 
> 

Glad to hear it!

Sorry for staggering my testing methodology over multiple emails, but I
should add for clarification and completeness: to exercise your change
to vubr_parse_host_port(), I passed various input into the -l and -r
options of vhost-user-bridge; and, with:

   tcpdump -i lo -n -X udp port 5678

while running:

   ./build/tests/vhost-user-bridge -H -l 127.0.0.1:4567 -r 127.0.0.1:5678

for example,

I was able to monitor the traffic (ARP requests) from port 4567 to 5678.

Yodel