[Qt-creator] optimization and file size between versions

[Duane]

On 10/1/2013 8:48 AM, Ziller Eike wrote:
>
> 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.

But one would expect an executable to be a release build if one switches 
to release build.  Do you mean that this doesn't guarantee that debug 
info won't be added to the file?

When I have a chance, I will rebuild 4.8.4 or 4.8.5 and see if this 
behavior goes away.  Since I don't see anyone with similar issues, I 
imagine that it's something with my builds of the Qt versions.  At the 
moment I don't have any pressing reason to move from 4.8.1 to a later 
Qt4 and we're not ready to move to Qt5.