Re: [PATCH] build-sys: error when slirp is not found and not disabled

[Thomas Huth <thuth@redhat.com>]

On 03/10/2022 12.48, Christian Schoenebeck wrote:
> On Montag, 3. Oktober 2022 10:05:14 CEST Daniel P. Berrangé wrote:
>> On Mon, Oct 03, 2022 at 11:05:34AM +0400, marcandre.lureau@redhat.com wrote:
>>> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>>>
>>> This is an alternative configure-time solution to "[PATCH] net:
>>> print a more actionable error when slirp is not found".
>>>
>>> See also "If your networking is failing after updating to the latest git
>>> version of QEMU..." ML thread.
>>>
>>> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>>> ---
>>>
>>>   meson.build | 6 ++++++
>>>   1 file changed, 6 insertions(+)
>>>
>>> diff --git a/meson.build b/meson.build
>>> index 8dc661363f..565096001d 100644
>>> --- a/meson.build
>>> +++ b/meson.build
>>> @@ -657,6 +657,12 @@ if not get_option('slirp').auto() or have_system
>>>
>>>     endif
>>>   
>>>   endif
>>>
>>> +if not get_option('slirp').disabled() and not slirp.found()
>>> +  error('libslirp is not explicitely disabled and was not found. ' +
>>> +        'Since qemu 7.2, libslirp is no longer included as a submodule '
>>> +
>>> +        'fallback, you must install it on your system or
>>> --disable-libslirp.') +endif

s/--disable-libslirp/--disable-slirp/

>> I understand the motivation, but this goes against the main principal
>> of our build time detection, which is to "do the right thing" automatically.
>> If libslirp is not present on the host, then I would consider the need to
>> pass --disable-libslirp to be a bug.
>>
>> I think this pain that people see of loosing slirp support is going to be
>> a pretty short term problem. IMHO it suffices to print a warning message
>> right at the very end of configure, after everything else, just for one
>> or two releases.
> 
> I guess that many users would find it a bug as well if this core feature just
> stops working. Even if you add a warning; what will probably happen is that
> packages are first built without. You want to risk that backlash, users filing
> reports, etc?
> 
> What about using this error for couple releases and then restoring symmetry?

I think that's a good compromise. Marc-André, could you maybe add a comment 
in front of your new code, saying something like "This is a temporary 
solution, remove after QEMU 8.1 has been released"?

  Thomas