Found the following significant warnings:
  abctools.c:14:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:29:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:54:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:79:12: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:80:12: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:81:12: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:81:6: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a previous declaration [-Wdeprecated-non-prototype]
  abctools.c:82:12: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:71:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:126:16: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:141:13: warning: passing arguments to 'distanceij' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:105:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:195:13: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:172:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:250:13: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  abctools.c:259:9: warning: passing arguments to 'norm2' without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:242:6: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  abctools.c:250:8: warning: a function declaration without a prototype is deprecated in all versions of C and is treated as a zero-parameter prototype in C2x, conflicting with a subsequent definition [-Wdeprecated-non-prototype]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/abctools.Rcheck/00install.out' for details.