cc -O2 -pipe  -pthread  -Wall -Wextra -Werror=implicit-function-declaration wchar/wcpncpy.c -o wchar/wcpncpy -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread 
wchar/wcpncpy.c:7:32: warning: unknown warning group '-Wstringop-truncation', ignored [-Wunknown-warning-option]
    7 | #pragma GCC diagnostic ignored "-Wstringop-truncation"
      |                                ^
wchar/wcpncpy.c:13:7: error: call to undeclared function 'wcpncpy'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
   13 |         if ( wcpncpy(dst, src, 4) != dst + 4 )
      |              ^
wchar/wcpncpy.c:13:7: note: did you mean 'wcsncpy'?
/usr/include/wchar.h:137:10: note: 'wcsncpy' declared here
  137 | wchar_t *wcsncpy(wchar_t * __restrict , const wchar_t * __restrict,
      |          ^
wchar/wcpncpy.c:13:28: warning: comparison between pointer and integer ('int' and 'wchar_t *' (aka 'int *')) [-Wpointer-integer-compare]
   13 |         if ( wcpncpy(dst, src, 4) != dst + 4 )
      |              ~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~
2 warnings and 1 error generated.