Hi Konstantinos. For your information, I finally succeeded in installing GetFEM, by downloading the current development version!
Here is the good configure script, working on my Apple Silicon machine:
./configure CXX=g++-13 CC='gcc-13 -arch arm64 -ld_classic' CXXFLAGS='-arch arm64
-ld_classic -no-pie -I/opt/homebrew/Cellar/qhull/2020.2/include' FC='gfortran-13 -arch arm64
-ld_classic' CXXCPP='g++-13 -E -arch arm64 -ld_classic' CPP='g++-13 -E -arch arm64
-ld_classic' --enable-metis --enable-python --enable-matlab=no --enable-shared
--disable-dependency-tracking --prefix=/opt/homebrew/ --enable-superlu
LDFLAGS='-L/opt/homebrew/Cellar/superlu/7.0.0/lib -L/opt/homebrew/Cellar/qhull/2020.2/lib'
--with-superlu-include-dir=/opt/homebrew/Cellar/superlu/7.0.0/include
So, in the end, it worked also with gcc-13 and not necessarily clang (I didn’t even have to set gcc-13 and g++-13 as default compilers), and so I believe the problem was not really a compatibility issue with clang, but rather something that didn’t work well with version 5.4.2.