backend_sources += files(
  'spgdoinsert.c',
  'spginsert.c',
  'spgkdtreeproc.c',
  'spgproc.c',
  'spgquadtreeproc.c',
  'spgscan.c',
  'spgtextproc.c',
  'spgutils.c',
  'spgvacuum.c',
  'spgvalidate.c',
  'spgxlog.c',
)