[Interest] Qt5 cannot be build on Debian Wheezy? GLIBCXX_3.4.20' not found

[Thiago Macieira]

On Sunday 18 January 2015 15:22:25 Jan Kundrát wrote:
> On Sunday, 18 January 2015 01:21:13 CEST, Thiago Macieira wrote:
> > It's always a bad idea to compile while the old version's
> > development files are present. Prefer to remove them.
> 
> This will break upgrades on Gentoo Linux. On Gentoo, the installed package
> always contains both headers and the produced libraries, and it's installed
> into the system's rootfs as a single unit.
> 
> I would suggest fixing the build system so that it doesn't try to use stuff
> from system's headers.

It can't always be. Think of when you're building something besides qtbase 
(let's say qtsvg) and qtbase is the system one. You'd expect the build to do:

	-I$QTDIR/include -I$QTDIR/include/QtCore -I$QTDIR/include/QtGui

But then you have includes like:

#include <QtSvg/qsvggenerator.h>

which will match the first -I. In this case, it's easy: we need to make sure 
that the build's own headers are before those above, but it's not that easy 
since the include path flags come from multiple sources and the order isn't 
always obvious.

So the recommendation stands: remove the old development files from the target.
-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center