... x86_64-pc-linux-gnu-g++ -Wl,--no-demangle,--hash-style=gnu,--as-needed,--gc-sections,--icf=safe -Wl,--no-undefined -fuse-ld=gold -Wl,--enable-new-dtags -shared -o libqjpeg.so .obj/qjpeghandler.o .obj/main.o .obj/moc_main.o -L/usr/lib -ljpeg -L/var/tmp/portage/dev-qt/qtgui-5.9999/work/qtgui-5.9999_build/lib -lQt5Gui -lQt5Core -lGL -lpthread .obj/qjpeghandler.o:qjpeghandler.cpp:function _ZN12QJpegHandlerC2Ev: error: undefined reference to '_Z26qt_convert_rgb888_to_rgb32PjPKhi' .obj/qjpeghandler.o:qjpeghandler.cpp:function _ZN12QJpegHandler5writeERK6QImage: error: undefined reference to '_Z17qt_imageTransformR6QImage6QFlagsIN15QImageIOHandler14Trans formationEE' collect2: error: ld returned 1 exit status Makefile:129: recipe for target '../../../../plugins/imageformats/libqjpeg.so' failed Reproducible: Always
qtcore-5.9999 also fails.
Don't CC teams if you can't assign bugs. You also failed to provide a full build log and your emerge --info.
It has nothing to do with a specific compiler version. Look it the link command: -L/usr/lib -ljpeg -L/var/tmp/portage/dev-qt/qtgui-5.9999/work/qtgui-5.9999_build/lib -lQt5Gui This will use the already installed /usr/lib64/libQt5Gui.so.5.4 library and not the intended /var/tmp/portage/dev-qt/qtgui-5.5.0/work/qtbase-opensource-src-5.5.0/lib//libQt5Gui.so.5.4. The "-L/usr/lib -ljpeg" part must come after -L/var/tmp/portage/dev-qt/qtgui-5.9999/work/qtgui-5.9999_build/lib -lQt5Gui
It should read: /var/tmp/portage/dev-qt/qtgui-5.5.0/work/qtbase-opensource-src-5.5.0/lib//libQt5Gui.so.5.5 of course. Copy&paste error.
I have opened https://bugreports.qt.io/browse/QTBUG-48255
Can't reproduce, I don't have that -L/usr/lib in my command line. You still haven't provided the requested info.