Hi Kai (and Everyone)!
On Wed, Apr 17, 2013 at 2:50 AM, Koehne Kai <kai.koe...@digia.com> wrote:
>
>> -----Original Message-----
>> From: interest-bounces+kai.koehne=digia....@qt-project.org
>>
>> Hello List!
>>
>> When I am using qmake to build a project that uses Qt, what is the best way
>> to turn on the compiler flag "-std=gnu++11"? (I am using a mingw-w64 build
>> of g++ 4.8.1.)
>
> qmake -r QMAKE_CXXFLAGS+=-std=gnu++11
>
>> Ideally, I would like to do this on a "global" basis, and not have to do it
>> for
>> each project separately (but that's not essential).
>
> I'd personally advise against using any kind of magic here, just pass it to
> qmake explicitly.
First off, I understand that my schemes lack the Qt good-housekeeping
seal of approval ... If I hack around with the Qt-provided files, I'd better
be careful and remember what hacks I hacked.
> If you really want to go down this route, you could also create a custom
> mkspec (say linux-g++-c++11) under mkspecs by copying your default one, and
> adding QMAKE_CXXFLAGS+=-std=gnu++11 to linux-g++-c++11/qmake.conf. You could
> then set the QMAKESPEC environment variable to
> $QTDIR/mkspecs/linux-g++-c++11. Anyhow, the next time you get 'weird' errors
> you better remember the magic :)
Okay, here's my scheme and how I am hoping it will work. I don't
really understand how qmake and the configuration process work
together, so please let me know if I've got something wrong.
I will be building natively with mingw-w64, so I believe the only thing
that is relevant is mkspecs\win32-g++-4.6.
1) Leave mkspecs\win32-g++-4.6\qmake.conf unmodified (i.e., don't
add "-std=gnu++11" to it), run
configure -platform=win32-g++-4.6 (and things like -no-qt3support)
and
mingw32-make
This should build Qt normally (i.e., no "-std=gnu++11").
2) Edit mkspecs\win32-g++-4.6\qmake.conf to contain
QMAKE_CXXFLAGS *= -std=gnu++11 -fno-keep-inline-dllexport
3) Use c++11 features in the code for my Qt project, and build with
qmake
mingw32-make
My theory is the the qmake-generated makefiles that get processed by
mingw32-make will have "-std=gnu++11" in the g++ compile commands.
More specifically my theory is that running
configure -platform=win32-g++-4.6
somehow sets up qmake to use whatever is in
mkspecs\win32-g++-4.6\qmake.conf
at the time qmake is run, even if qmake.conf gets modified after the
cinfigure step (rather than copying the unmodified contents of qmake.conf
somehow into qmake).
So, that's my scheme. Do you think it will work as I imagine (even if
it doesn't have the Qt good-housekeeping seal of approval)?
> Finally, how about switching to Qt 5 ? Qt 5 is compiled with c++11 enabled by
> default, and you can enable it for your own projects by doing CONFIG+=c++11
> (qmake based projects).
Yes, upgrading to Qt 5 is on my list. For me, c++11 and Qt 5 are both
big enough steps that I thought I'd be conservative, and take them one
at a time.
> Regards
>
> Kai
Thanks for everyone's advice.
And ...
Happy C++11 Hacking!
.K. Frank
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