Ebuild calls c++ rather than the arch compiler From the build log: [...] cd /var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1_build/math && /usr/bin/c++ -DBOOST_MULTI_INDEX_DISABLE_SERIALIZATION -DBOOST_TEST_DYN_LINK -D_BIND_TO_CURRENT_VCLIBS_VERSION=1 -march=native -O2 -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/. -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/foundation -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/math -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/interaction -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/zones -I/usr/include/qt4/QtDesigner -I/usr/include/qt4/QtScriptTools -I/usr/include/qt4/QtXml -I/usr/include/qt4/QtSql -I/usr/include/qt4/QtOpenGL -I/usr/include/qt4/QtNetwork -I/usr/include/qt4/QtXmlPatterns -I/usr/include/qt4/QtWebKit -I/usr/include/qt4/QtUiTools -I/usr/include/qt4/QtTest -I/usr/include/qt4/QtScript -I/usr/include/qt4/QtSvg -I/usr/include/qt4/Qt3Support -I/usr/include/qt4/QtGui -I/usr/include/qt4/QtCore -I/usr/share/qt4/mkspecs/default -I/usr/include/qt4 -I/var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1_build/math -pthread -o CMakeFiles/math.dir/LinearSolver.cpp.o -c /var/tmp/portage/media-gfx/scantailor-0.9.11.1/work/scantailor-0.9.11.1/math/LinearSolver.cpp [...]
Fixed in the tree.