[vlc-devel] Support for Windows on Arm

[Martin Storsjö]

On Fri, 9 Sep 2022, Pierrick Bouvier wrote:

> On 9/9/22 10:39, Martin Storsjö wrote:
>> On Fri, 9 Sep 2022, Pierre Lamot wrote:
>> 
>>> 
>>> On 09/09/2022 10:29, Steve Lhomme wrote:
>>>> out of the box for Windows ARM. It should build like the other Windows
>>>> targets except adding `-a aarch64` to build.sh. It should work with
>>>> the LLVM Dockers we use (or any llvm-mingw build). Not sure there's
>>>> mingw-w64 for ARM available.
>>>> 
>>>> There may be some contribs that don't build properly, for example Qt
>>>> may refuse to build or not understand what's going on. And if it
>>>> builds it's not
>>> 
>>> according to your website [1], qt for windows arm requires version 6.2,
>>> but we only support Qt 5, so this may indeed be a problem if you plan to
>>> build the UI
>> 
>> I dunno what that information that website is based on, but with upstream
>> Qt (plain Qt Core) it has worked fine since around Qt 5.11 with
>> llvm-mingw. Maybe it's based on what they have tested themselves?
>> 
>> It runs just fine with the Qt backported patches in VLC's contrib, on both
>> the 3.0.x and master branches.
>> 
>
> We observed issues with previous version. For instance, with cmake-gui that 
> is crashing on startup. It's good to know it's working for VLC.

Ok, that's good to know. FWIW, if there's an issue with older versions but 
which is fixed in newer ones, it's usually quite straightforward to do a 
reverse bisect to find out which commit fixed it, and then backport that 
one to the version of Qt that is used. (VLC carries half a dozen of 
backported Qt patches, for building the ancient Qt 5.6 with modern 
compilers.)

> Officially, Qt is advertising support for Windows on Arm from Qt6 [1], while 
> Qt5 does not mention it [2]. In more, prebuilt versions are only available 
> since Qt6. Not every project builds Qt from source ;).

Well the prebuilt binaries don't really help people in the mingw ecosystem 
anyway, as those are MSVC only. And in practice I don't know of any more 
concrete efforts from Qt's side here (but I may have missed something) 
other than doing regular builds of it. But for sure, newer versions 
generally do come with more fixes that need to be backported if using 
older versions.

// Martin