Dear CMake developers, I'm a newbie to CMake (I've never written any project myself), but while trying to install a physics package Root from the master of https://github.com/bbannier/ROOT (https://root.cern.ch/svn/root/trunk) I realised that an unsupported compiler flag "-arch x86_64" mysteriously sneaks into Fortran_FLAGS when -DCMAKE_OSX_ARCHITECTURES="x86_64" is passed to cmake. That flag CMAKE_OSX_ARCHITECTURES is added automatically to all projects in MacPorts (third-party package manager for Mac OS X) even when cross-compiling or compilation of fat binaries (like i386+x86_64) is not needed.
The g95 compiler ignores "-arch <...>" flag, but GCC's gfortran 4.x throws an error and breaks compilation. I could probably try to prevent DCMAKE_OSX_ARCHITECTURES from being passed to cmake (via some tricks in MacPorts or by modifying MacPorts sources), but I still believe that passing "-arch x86_64" to Fortran_FLAGS is a bug in CMake. I tried to figure out when those flags are set, but I don't know enough about CMake. I've seen several places where compiler flags are simply copied from C to Fortran, for example here: # Create a set of shared library variable specific to Fortran # For 90% of the systems, these are the same flags as the C versions # so if these are not set just copy the flags from the c version if(NOT DEFINED CMAKE_SHARED_LIBRARY_CREATE_Fortran_FLAGS) set(CMAKE_SHARED_LIBRARY_CREATE_Fortran_FLAGS ${CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS}) endif() but I don't have enough knowledge to be able to track the problem down to a single spot. There is a slight chance that the problematic flag is introduced by the project, but there are other projects in MacPorts suffering from the same symptoms. The command that I used to compile Root: cmake \ -DCMAKE_Fortran_COMPILER=/opt/local/bin/gfortran-mp-4.5 \ -DCMAKE_C_COMPILER=/usr/bin/clang \ -DCMAKE_CXX_COMPILER=/usr/bin/clang++ \ -DCMAKE_INSTALL_PREFIX=/path/to/install \ -DCMAKE_OSX_ARCHITECTURES="x86_64" ../root_trunk In case that anyone would want to try it on the particular project, the generated file misc/minicern/CMakeFiles/minicern.dir/flags.make ends up containing the following variables (among others): C_FLAGS = -m64 -pipe -W -Wall -fsigned-char -fno-common -O2 -g -arch x86_64 -fPIC -I<path/to/some/include/dirs> Fortran_FLAGS = -m64 -std=legacy -arch x86_64 -fPIC -I<path/to/some/include/dirs> (Another problem is that -std=legacy is not recognised by g95 and throws another error, but that one is a bug in the project.) I also didn't know how to disable Fortran compiler altogether, but that's a completely different issue. I'm using 64-bit Mac OS X 10.7.4, cmake version 2.8.10. I would be very grateful for any insight about how to get rid of that "-arch x86_64" flag. Thanks and best regards, Mojca Related tickets: - https://trac.macports.org/ticket/37732 (about the -arch flag in Fortran) - https://trac.macports.org/ticket/37688 ([also] about development of a package for Root using CMake) - https://savannah.cern.ch/bugs/index.php?99944 (not strictly related though) -- Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Follow this link to subscribe/unsubscribe: http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers