[Interest] Size of libQt5Core in 5.3

[Daniel Bowen]

I have an embedded environment where we use non-UI parts of Qt (Qt Core, Qt
Networking) on an ARM host processor.

We've been using 4.8.4 for a little while. There's some other changes coming
to this code, and we've been looking to move to 5.x with the upcoming 5.3.
After working through several issues, I got the release candidate of Qt 5.3
compiled for this processor.  At first, libQt5Core.so.5.3.0 was 6.6 MB!
With 4.8.4, we were able to get libQtCore4 down to 2.6 MB.

So I started putting in -skip, -no-feature, etc. having features we would
still use, but other things stripped out. I also had a mkspec use -Os to
optimize for size. Using something like this:

OPENSSL_LIBS="-L(path for openssl) -lssl -lcrypto" ./configure -release
-opensource -prefix (path for prefix) -extprefix (path for prefix) -shared
-largefile -I (path for jpeg) -L (path for jpeg) -sysroot (path for sysroot)
-xplatform linux-arm_v5t_le-g++ -confirm-license -system-zlib -system-libpng
-system-libjpeg -openssl-linked -no-accessibility -no-freetype -no-harfbuzz
-no-glib -no-gui -no-widgets -no-cups -no-iconv -no-evdev -no-icu
-no-fontconfig -no-pch -no-dbus -no-xcb -no-directfb -no-linuxfb -no-kms
-no-opengl -nomake examples -nomake tests -skip qtdeclarative -skip qtdoc
-skip qtgraphicaleffects -skip qtlocation -skip qtquick1 -skip
qtquickcontrols -skip qtscript -skip qttranslations -skip qtwebkit -skip
qtwebkit-examples -skip qtx11extras -skip qtxmlpatterns
-no-feature-TEXTHTMLPARSER -no-feature-TEXTODFWRITER -no-feature-CSSPARSER
-no-feature-CONCURRENT -no-feature-DRAGANDDROP -no-feature-SESSIONMANAGER
-no-feature-SHORTCUT -no-feature-ACTION -no-feature-DOM
-no-feature-FILESYSTEMMODEL -no-feature-FILESYSTEMWATCHER
-no-feature-ITEMVIEWS -no-feature-DIRMODEL -no-feature-STANDARDITEMMODEL
-no-feature-PROXYMODEL -no-feature-SORTFILTERPROXYMODEL
-no-feature-IDENTITYPROXYMODEL -no-feature-STRINGLISTMODEL
-no-feature-LISTVIEW -no-feature-TABLEVIEW -no-feature-TREEVIEW
-no-feature-DATAWIDGETMAPPER -no-feature-COLUMNVIEW -no-feature-MOVIE
-no-feature-IMAGEFORMAT_PPM -no-feature-IMAGEFORMAT_XBM
-no-feature-IMAGEFORMAT_XPM -no-feature-FREETYPE -no-feature-BIG_CODECS
-no-feature-ICONV -no-feature-FTP -no-feature-ACCESSIBILITY
-no-feature-ANIMATION -no-feature-STATEMACHINE -no-feature-GESTURES
-no-feature-DBUS -no-feature-XMLSCHEMA -verbose

It went down to 5.3 MB. 5.3 MB was still too bit, so I went through the
features from qfeatures.txt, and did "-no-feature" for every single feature
listed.  libQt5Core wouldn't compile without LIBRARY, SETTINGS and
REGULAREXPRESSION, so I took the "-no-feature" out for those things.  Even
with all of that removed, libQt5Core.so.5.3.0 was still 4.3 MB after being
stripped.  That would have some things removed though that we want.

Is there any way to get Qt Core to compile smaller, like under 3MB? Am I
missing anything to skip or "-no-xyz" or "-nomake" or "-no-feature"?  Why is
libQt5Core.so.5.3.0 so much bigger than libQtCore4.so.4.8.4?

We may just need to move to 4.8.6 and leave it there instead of jumping onto
5.x.

Thanks,
-Daniel
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