Upgrade to Qt 4.5

[Matthew Woehlke]

Alejandro Exojo wrote:
> El Mi�rcoles, 11 de Marzo de 2009, David escribi�:
>> Maybe I am wrong, but it is the safest way, and it costs only a couple of
>> hours, so it's worth try it to avoid possible problems :)
> 
> And do you recompile everything in your system each time you upgrade GCC

If you run gentoo, you *should* recompile after a major gcc upgrade (on 
the theory that you'll get better, faster code by doing so) :-).

> or  libc?

Again, on gentoo I would consider it :-). And I bet you'd be surprised 
the extent to which most distros usually have software built against the 
latest glibc.

Another reason I rebuild is it's a good excuse to nuke the install tree 
and make sure there's no cruft floating around. That's usually not an 
issue when you're dealing with distro packages, but it *is* (or at 
least, can be) when you're overwriting an install on a regular basis 
with no clean-up happening in between. And while CMake is far better 
than most build systems about always rebuilding anything that needs to 
rebuild, like any software there is a possibility of bugs, both in CMake 
and in KDE's build system.

Also, there is a very good reason why you *should* rebuild; to take 
advantage of new features, and to allow compatibility code to die. I 
know KDE picks up the occasional #ifdef based on Qt version. In some 
cases, rebuilding will improve things, enable new features, etc. In some 
(less common) cases, things may be *genuinely broken* if the 4.4 code is 
used with 4.5.

Finally, all the header changes mean that the next "incremental" build 
will likely be nothing of the sort, regardless, so there's something to 
be said for "getting it over with". (On an unrelated note, I feel sorry 
for the non-native-en_US people that will be trying to parse that 
expression; I was born en_US and *I'm* having trouble :-).)

All that said... there's an excellent chance that nothing bad will 
happen if you don't rebuild. I just don't think you should be insulting 
people that *do* run full rebuilds on major Qt updates. (Or else, you 
should choose your words more carefully so you don't seem to be doing so 
;-).)

-- 
Matthew
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(It seemed appropriate...)

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