[Qt-creator] optimization and file size between versions

[Ziller Eike]

On 30.09.2013, at 17:44, Duane <duane.hebert at group-upc.com> wrote:

> On 9/30/2013 3:14 AM, Ziller Eike wrote:
>> 
>> On 29.09.2013, at 16:22, Oleksii Serdiuk <contacts at oleksii.name> wrote:
>> 
>>> Hello Dane,
>>> 
>>> Do you build Qt yourself? Prebuilt Qt binaries always default to release build (CONFIG+=release), unless you pass CONFIG+=debug to qmake. However, when you build Qt yourself, depending on configure options you specify, it can default to debug build (CONFIG+=debug) and you have to specify CONFIG+=release explicitly if you want to build in release mode. AFAIK, Qt Creator assumes that Qt defaults to release build so it doesn't explicitly pass CONFIG+=release to qmake.
>> 
>> Qt Creator actually looks into what you Qt does by default, and then only passes CONFIG+=release or CONFIG+=debug if needed.
>> The most reliable way to find out if you do a release or debug build is to look for -g options on your gcc command lines.
>> 
>>>>>> […]
>>>>>> Try adding "QT=" to your project.
>>>>>> 
>>>>> 
>>>>> 
>>>>> Didn't help.  One thing that I do notice is that I don't see +=Release
>>>>> in the build string:
>>>>> 
>>>>> 10:04:08: Starting: "/usr/bin/qmake-qt4"
>>>>> /home/duane/QtSDK/PT500Projects/visu32/visu32.pro -r -spec linux-g++
>>>>> 10:04:08: The process "/usr/bin/qmake-qt4" exited normally.
>>>>> 10:04:09: Starting: "/usr/bin/make"
>>>>> g++ -c -pipe -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2
>> 
>> You have -O2 -g here, so "optimized with debug info" which is something that I think Qt normally doesn't do. Did you manually override compiler flags, or touch the mkspecs?
>> The presence or absence of -O flags can also result in different code size, though I'd guess not in the magnitude that you experience?
>> 
> 
> Hmmm.  No, I haven't messed with the make specs and I don't think I've 
> changed any compiler flags.  I just built a new 4.8.1 and switched to 
> that and I don't have any problems.  The resulting files on 12 of my 
> projects match what my colleague's results are.  There must be something 
> in the build of the 4.8.4 and 5.2 versions.
> 
> My build output with the 4.8.1 version is now:
> 
> g++ -c -pipe -O2 -Wall -W -Wno-write-strings -Wno-unused-parameter 
> -Wno-unused-variable -DBPP32 -DPT470BUILD 
> -I/usr/local/Trolltech/Qt-4.8.1/mkspecs/linux-g++ -I. 
> -I../../../SVN_Repos/PT470Development/src/include 
> -I../../../SVN_Repos/PT470Development/OpenGUI/src 
> -I../../../SVN_Repos/PT470Development/OpenGUI/src -o main.o 
> ../../../SVN_Repos/PT470Development/src/visu32/main.cpp
> 
> no -g
> 
> So maybe it was using debug.  But shouldn't that be enabled/disabled 
> from the debug/release switch in the ide?

The debug/release switch tells qmake CONFIG+=release or CONFIG+=debug. What qmake does with that is qmake's business.

++ Eike

> <snip>
> 
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-- 
Eike Ziller, Senior Software Engineer - Digia, Qt
 
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