[vlc-devel] Patches to work-around __packed__ on iOS

[Rémi Denis-Courmont]

Le lundi 26 mars 2012 19:53:59 Felix Paul Kühne, vous avez écrit :
> Sorry, but this is the intention. Using __packed__ leads to memory
> alignment issues when running the code on ARM (especially in src/input in
> the time shift code).

Sorry but I think you didn't get the point. With that patch, the compiled 
executable CODE WILL NOT WORK PROPERLY.

If packing is not needed, it should be removed. If packing is needed (and it 
probably is in this case), then this patch is just wrong.

> This obviously does not happen on x86 or PPC platforms.

To the contrary, the whole point of the packing is to force unaligned 
structures regardless of the target constraints. Obviously, the compiler needs 
to emit memcpy() on architectures that do not support unaligned loads or 
stores.

> Yes, the correct approach here would be to use a non-broken compiler.
> Regrettably, such a thing isn't available for production releases at this
> point.

I don't claim the compiler is broken and I never did. Indeed, packing is a 
common but nevertheless non-standard language extension. But _broken_ code is 
not an option, regardless of the bugs or limitations in the toolchain.

By the way, the correct portable solution was already discussed earlier this 
month regarding OGG.

-- 
Rémi Denis-Courmont
http://www.remlab.net/
http://fi.linkedin.com/in/remidenis