Somehow using a custom build_ext subclass always triggered a failing rebuild when testing: /usr/lib/ccache/g++-10 -pthread -shared -Wl,-O1 -Wl,-Bsymbolic-functions -Wl,-z,relro -g -fwrapv -O2 -Wl,-z,relro -g -fwrapv -O2 -g -ffile-prefix-map=/build/python3.9-RNBry6/python3.9-3.9.2=. -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 build/temp.linux-x86_64-3.9/cxx/builtin_pybind11.o build/temp.linux-x86_64-3.9/cxx/connection.o build/temp.linux-x86_64-3.9/cxx/converters.o build/temp.linux-x86_64-3.9/cxx/deck.o build/temp.linux-x86_64-3.9/cxx/deck_keyword.o build/temp.linux-x86_64-3.9/cxx/eclipse_config.o build/temp.linux-x86_64-3.9/cxx/eclipse_grid.o build/temp.linux-x86_64-3.9/cxx/eclipse_io.o build/temp.linux-x86_64-3.9/cxx/eclipse_state.o build/temp.linux-x86_64-3.9/cxx/emodel_util.o build/temp.linux-x86_64-3.9/cxx/export.o build/temp.linux-x86_64-3.9/cxx/field_props.o build/temp.linux-x86_64-3.9/cxx/group.o build/temp.linux-x86_64-3.9/cxx/log.o build/temp.linux-x86_64-3.9/cxx/parsecontext.o build/temp.linux-x86_64-3.9/cxx/parser.o build/temp.linux-x86_64-3.9/cxx/schedule.o build/temp.linux-x86_64-3.9/cxx/summary_state.o build/temp.linux-x86_64-3.9/cxx/table_manager.o build/temp.linux-x86_64-3.9/cxx/unit_system.o build/temp.linux-x86_64-3.9/cxx/well.o -lopmcommon -lboost_system -lstdc++fs -o build/lib.linux-x86_64-3.9/opm/libopmcommon_python.cpython-39-x86_64-linux-gnu.so -fopenmp /usr/lib/x86_64-linux-gnu/libfmt.so.7.1.3 error: can't copy 'build/lib.linux-x86_64-3.9/opm/libopmcommon_python.cpython-39-x86_64-linux-gnu.so': doesn't exist or not a regular file Therefore we resort to only setting the CC and CXX variables to the C++ compiler. Note that one cannot use "ccache c++" for CXX. With the default build_ext the problem vanishes.
Python bindings for the OPM-common module of the Open Porous Media project.