clang: anuga/pymetis/metis-4.0/mkwayrefine.c
anuga/pymetis/metis-4.0/mkmetis.c:118:3: error: implicit declaration of function '__GKfree' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  GKfree(&graph->nvwgt, &graph->npwgts, &graph->gdata, &graph->rdata, LTERM);
  ^
anuga/pymetis/metis-4.0/rename.h:380:19: note: expanded from macro 'GKfree'
#define GKfree                          __GKfree
                                        ^
1 error generated.
error: Command "/Users/Adam/spack/lib/spack/env/clang/clang -I/Users/Adam/spack/opt/spack/darwin-catalina-x86_64/apple-clang-12.0.0/py-numpy-1.16.6-cng2utdpywj4ogtenzds7gy2qct3avmx/lib/python2.7/site-packages/numpy/core/include -Ianuga/pymetis/metis-4.0 -I/Users/Adam/spack/opt/spack/darwin-catalina-x86_64/apple-clang-12.0.0/python-2.7.18-ivj7xnmfip7afijbbkbuijiihi7ds4g5/include/python2.7 -c anuga/pymetis/metis-4.0/mkmetis.c -o build/temp.macosx-10.15.7-x86_64-2.7/anuga/pymetis/metis-4.0/mkmetis.o -MMD -MF build/temp.macosx-10.15.7-x86_64-2.7/anuga/pymetis/metis-4.0/mkmetis.o.d" failed with exit status 1clang: anuga/pymetis/metis-4.0/subdomains.c

clang: anuga/pymetis/metis-4.0/srefine.c
clang: anuga/pymetis/metis-4.0/frename.c
clang: anuga/pymetis/metis-4.0/mmatch.c
anuga/pymetis/metis-4.0/subdomains.c:885:3: error: implicit declaration of function '__GKfree' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  GKfree(&cand, &cand2, LTERM);
  ^
anuga/pymetis/metis-4.0/rename.h:380:19: note: expanded from macro 'GKfree'
#define GKfree                          __GKfree
                                        ^
1 error generated.