Found the following significant warnings:
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNifti.h:58:35: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./RNifti_shim.h:19:30: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:268:28: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:669:29: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:687:27: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:706:23: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:722:38: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/RNifti/include/RNiftiAPI.h:739:30: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  RNifti_shim.c:39:30: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./print.h:15:18: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  core.c:717:19: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  core.c:751:24: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  core.c:774:24: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/imbibe.Rcheck/00install.out' for details.