[CMake] [PATCH] FindQt4.cmake qt4_automoc improvements

Tanguy Krotoff tkrotoff at gmail.com
Tue May 27 14:05:46 EDT 2008


> I'm curious what the timings are with and without the include paths.  Can you
> give some data?
> If I remember right, this thread started by talking about compile times.

That's right!
I just tried on phonon-vlc-mplayer http://code.google.com/p/phonon-vlc-mplayer/
the timing argument just is not an argument as I thought:


1) with no Qt modules included

$time make
real	2m57.113s -> 177s
user	2m42.906s
sys	0m12.297s

2) with all Qt modules included

$time make
real	3m5.236s -> 185s
user	2m49.619s
sys	0m13.941s


As you see, there is almost no difference, not even 5%.


Historically I was convince that timing differences where huge: on
another project, 2 years ago, using SCons, a colleague convince me
that using #include <QtGui/Q..> was useful with compilation time
almost divided by 2.
I guess after this small test, that the good timings that we got were
due to SCons not handling -I in a proper way. (SCons is/was not
scalable)

I think the best now is probably not to modify UseQt4.cmake and I will
stick with my small macro that optimize the include path as I prefer
to have a smaller include path (more readable and easier to debug).

-- 
Tanguy Krotoff <tkrotoff at gmail.com>
+33 6 68 42 70 24


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