Found the following significant warnings:
  ./zzz.h:4:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./zzz.h:6:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  zzz.c:22:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  zzz.c:58:15: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.h:69:19: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.h:70:23: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.h:128:35: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.h:129:41: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.c:310:50: 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]
  onig/st.c:856:6: 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]
  onig/st.c:892:16: 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]
  onig/st.c:933:16: 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]
  onig/st.c:975:15: 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]
  onig/st.c:1032:17: 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]
  onig/st.c:1483:46: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  onig/st.c:1505:18: 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]
  onig/st.c:1519:26: 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]
  onig/st.c:1567:38: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  enc/jis/props.kwd:106:1: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  enc/jis/props.kwd:155:1: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  onig/enc/unicode/name2ctype.h:33390:1: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
  onig/enc/unicode/name2ctype.h:35107:1: warning: a function definition 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/ore.Rcheck/00install.out' for details.