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

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

On 14/12/2025 11:47, Cédric Le Goater wrote:
> + Thomas,
> 
> On 12/14/25 17:18, Yodel Eldar wrote:
>>
>>
>> On 14/12/2025 02:56, Cédric Le Goater wrote:
>>> 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.
>>>
>>>
>>
>> Certainly, that's a great idea! Although, I'll need to get better
>> acquainted with QEMU's testing framework... Would you be willing to
>> answer the occasional question regarding scope, approach, conventions,
>> etc. over IRC? 
> 
> Sure. The #qemu channel is hosted on OFTC.
> 
> I think this test would qualify as a functional test. To run :
> 
>    $ make check-functional
> 
> You could get some inspiration out of test_virtio_gpu.py I suppose.
> Check source [2].
> 
> See [3] to send patches.
> 
> Thanks,
> 
> C.
> 
> [1] https://www.qemu.org/docs/master/devel/testing/main.html#functional- 
> tests-using-python
> [2] https://gitlab.com/qemu-project/qemu/-/blob/master/tests/functional/ 
> x86_64/test_virtio_gpu.py?ref_type=heads
> [3] https://www.qemu.org/docs/master/devel/submitting-a-patch.html
> 
> 

Thanks for the links!

Currently, the plan's to replace tcpdump with the -object filter-dump
feature and look for the user-supplied hosts and ports in the output,
though I suspect there's a better way to do that. This would essentially
only exercise vubr_parse_host_port() as in my manual testing of your
patch. Please let me know if you had another direction in mind.

My nick's "yodel" on OFTC, and I'll reach out if I hit a snag.

Thanks,
Yodel

>> There's a Co-authored-by tag with your name on it if
>> you so choose :-)
>>
>> Yodel
>>
> 
>