Found the following significant warnings:
  arch.h:135:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:136:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:137:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:138:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:139:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:140:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:141:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:142:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:143:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:144:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:145:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:146:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:147:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:148:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:149:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  arch.h:150:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  parser.h:116:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  module.h:294:57: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  module.h:295:57: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  library_mesh.c:79:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  library_random_f.c:82:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  module.h:242:37: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  module.h:243:37: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mesh_coarsen.c:71:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  wgraph_part_fm.h:149:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  wgraph_part_fm.c:909:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  main_esmumps.c:70:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:40:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:47:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:49:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:57:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:59:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:67:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:69:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:77:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.c:23:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.h:33:42: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.c:38:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.c:53:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_common.c:68:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_basic.h:154:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.h:36:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.h:37:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.h:38:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_basic.c:658:11: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io.h:136:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_thread.h:72:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_thread.c:243:11: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.c:45:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.c:53:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.c:61:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.c:67:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_io_err.c:73:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_numa.c:15:5: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_save_restore_C.h:29:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_config_file_C.h:21:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_thread_affinity.h:21:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mumps_c.c:58:46: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  dmumps_gpu.h:18:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  dmumps_gpu.c:19:17: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
See ‘/home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/rmumps.Rcheck/00install.out’ for details.