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

["Cédric Le Goater" <clg@redhat.com>]

Hello Yodel,

On 12/13/25 21:15, Yodel Eldar wrote:
> 
> 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.
> 

Would you mind providing a test case under tests/ or tests/functional ?

Thanks,

C.