[vlc-devel] [PATCH 2/2] thread: fix compilation with clang 7 or older

[Marvin Scholz]

Of course I would be fine with dropping support for old Clang
versions too, instead of this workaround.

If we decide to go that route we should add a configure check
though, so that when using a too old version there is a helpful
error instead of just the build at some point failing.

On 25 Feb 2020, at 11:44, Rémi Denis-Courmont wrote:

> Hi,
>
> Ubuntu LTS originally uses Clang 6 as default. But it has backports of 
> 7, 8 and 9 in the official repos.
>
> Le 25 février 2020 11:51:23 GMT+02:00, Thomas Guillem 
> <thomas at gllm.fr> a écrit :
>>
>>
>> On Tue, Feb 25, 2020, at 10:33, Alexandre Janniaux wrote:
>>> Hi,
>>>
>>> The main issue with requiring earlier version of Clang is
>>> that it needs to be shipped in android NDK release too.
>>>
>>> Currently it seems to be failing with android NDK 18 (which
>>> is previous VLC 3 NDK version) but is ok with NDK 21 (which
>>> is LTS and the current version on VLC 4 and latest VLC 3).
>>>
>>> Is it planned to drop support of NDK 18? (or done?).
>>
>> Yes, VLC 4.0 is NDK 21 only. It is building now with NDK 18 but we
>> shouldn't do anything to keep supporting it.
>>
>> So my question: is the clang issue only happening on NDK 18 ? If so, 
>> I
>> would tend to agree with Rémi.
>>
>> What other OS/distrib are still using clang 7 ?
>>
>>>
>>>> Especially not old bugs from a compiler that will be already 3
>> major releases behind by the time VLC 4.0 comes out, while on the 
>> other
>> hand C++ devs are craving to use C++17 and we require bleeding edge
>> version of some other build tools (Meson requirement is so new that 
>> you
>> can't build contribs on current Ubuntu LTS).
>>>
>>> I don't think toolchains and buildsystems are comparable
>>> with regards to version update. You can be stuck on old
>>> compilers but still be able to use bleeding edge build
>>> systems. The case of android is typically one of them.
>>>
>>> Regards,
>>> --
>>> Alexandre Janniaux
>>> Videolabs
>>>
>>> On Tue, Feb 25, 2020 at 11:06:20AM +0200, Rémi Denis-Courmont 
>>> wrote:
>>>> Hi,
>>>>
>>>> I don't think it makes sense in general to try to work around
>> compiler bugs.
>>>>
>>>> Especially not old bugs from a compiler that will be already 3
>> major releases behind by the time VLC 4.0 comes out, while on the 
>> other
>> hand C++ devs are craving to use C++17 and we require bleeding edge
>> version of some other build tools (Meson requirement is so new that 
>> you
>> can't build contribs on current Ubuntu LTS).
>>>>
>>>> Le 25 février 2020 10:24:33 GMT+02:00, Thomas Guillem
>> <thomas at gllm.fr> a écrit :
>>>>>
>>>>>
>>>>> On Tue, Feb 25, 2020, at 08:34, Rémi Denis-Courmont wrote:
>>>>>> Hi,
>>>>>>
>>>>>> Clang 7 supports what you call C17. It even has a compiler flag
>> for
>>>>> it explicitly. That's all in the LLVM and Clang documentation.
>>>>>>
>>>>>> Ergo it works or your compiler is buggy.
>>>>>
>>>>> I think that is what ePirat said, clang 7 has the bug.
>>>>>
>>>>> Could it be possible to enable this cast on a ifdef clang < 7 ?
>>>>>
>>>>> That way, we can easily remove later when we drop clang 7 support.
>>>>>
>>>>>>
>>>>>> Le 25 février 2020 08:36:39 GMT+02:00, Marvin Scholz
>>>>> <epirat07 at gmail.com> a écrit :
>>>>>>> On 25 Feb 2020, at 6:56, Rémi Denis-Courmont wrote:
>>>>>>>
>>>>>>>> Le maanantaina 24. helmikuuta 2020, 17.45.07 EET Marvin Scholz
>> a
>>>>>>>> écrit :
>>>>>>>>> even though it never modifies it.
>>>>>>>>> Clang versions 7 or older did implement this quite strictly
>> and
>>>>>>>>> therefore errors when compiling this code:
>>>>>>>> That's either a bug in that compiler version or possibly a
>> minor
>>>>>>>> update not
>>>>>>>> installed, or mistaken compiler flag (in other words,
>> configure
>>>>> script
>>>>>>>> bug).
>>>>>>>> Clang 7 officially supports C17/C18.
>>>>>>>
>>>>>>> I tested all major versions before 7 and all are affected.
>>>>>>> I can’t easily test minor versions between 7 or 8 as they are
>> not
>>>>>>> available
>>>>>>> on godbolt. Looking at the git repository though it seems the
>> first
>>>>>>> fixed
>>>>>>> version was 8.0.0.
>>>>>>>
>>>>>>> Not sure what you mean by mistaken compiler flag here?
>>>>>>>
>>>>>>>>
>>>>>>>>  And to call it C17 is a bit of a stretch. It's really just an
>>>>>>>>  re-edition of
>>>>>>>>  C11 with editorial corrections gathered. The atomic spelling
>> error
>>>>> was
>>>>>>>>  already
>>>>>>>>  found and corrected in 2014.
>>>>>>>
>>>>>>> It’s called C17 on open-std.org, thats why I used that here,
>> not
>>>>> sure
>>>>>>> what else to
>>>>>>> call it.
>>>>>>>
>>>>>>>>  --
>>>>>>>>  Реми Дёни-Курмон
>>>>>>>>  http://www.remlab.net/ vlc-devel mailing list
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>>>>>> --
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