I have 2 compilers installed: sys-devel/clang-3.9.0-r100 and sys-devel/gcc-4.9.4 make.conf contains CXX="clang++" With this setup calibre couldn't be built with neither clang nor gcc. Regardless of CXX chosen, calibre compiles some stuff using clang++, some stuff using g++. The error message: g++: error: unrecognized command line option ‘-std=c++1z’ I found this in one of generated Makefiles: CC = gcc CXX = g++ CXXFLAGS = -pipe -O2 -std=c++1z -fvisibility=hidden -fvisibility-inlines-hidden -Wall -W -D_REENTRANT -fPIC $(DEFINES) And in /usr/lib/qt5/mkspecs/qconfig.pri: QT_CONFIG += ... c++11 c++14 c++1z ... When I tried to run qmake directly on a test minimal .pro, it generated correct Makefile. When I rebuilt qtcore with gcc, it built calibre successfully, but some parts of calibre were using clang anyway (I had CXX=clang++ at that moment). I guess the errors would be reverse if gcc were new enough to support -std=c++1z and clang old enough to not support it. Reproducible: Always Steps to Reproduce: 1. Compile qtcore with clang 2. Try to compile calibre 3. Actual Results: Error Expected Results: Success
Created attachment 464968 [details] build.log
Created attachment 464970 [details] build environment
Created attachment 464972 [details] emerge --info '=app-text/calibre-2.78.0::gentoo'
Created attachment 464974 [details] generated headless.pro from build dir
Created attachment 464976 [details] generated Makefile
Created attachment 464978 [details] /usr/lib/qt5/mkspecs/qconfig.pri refering to clang
