cc -O2 -pipe  -pthread  -Wall -Wextra -Werror=implicit-function-declaration wchar/wcpcpy.c -o wchar/wcpcpy -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread 
wchar/wcpcpy.c:11:7: error: call to undeclared function 'wcpcpy'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
   11 |         if ( wcpcpy(dst, src) != dst + 7 )
      |              ^
wchar/wcpcpy.c:11:7: note: did you mean 'wcscpy'?
/usr/include/wchar.h:130:10: note: 'wcscpy' declared here
  130 | wchar_t *wcscpy(wchar_t * __restrict, const wchar_t * __restrict);
      |          ^
wchar/wcpcpy.c:11:24: warning: comparison between pointer and integer ('int' and 'wchar_t *' (aka 'int *')) [-Wpointer-integer-compare]
   11 |         if ( wcpcpy(dst, src) != dst + 7 )
      |              ~~~~~~~~~~~~~~~~ ^  ~~~~~~~
1 warning and 1 error generated.