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

Yodel