cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration wchar/wcscasecmp_l.c -o wchar/wcscasecmp_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
wchar/wcscasecmp_l.c:13:7: error: call to undeclared function 'wcscasecmp_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   13 |         if ( wcscasecmp_l(L"foo", L"FOO", locale) != 0 )
      |              ^
wchar/wcscasecmp_l.c:13:7: note: did you mean 'wcscasecmp'?
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_wchar.h:235:9: note: 'wcscasecmp' declared here
  235 | int     wcscasecmp(const wchar_t *, const wchar_t *) __OSX_AVAILABLE_STARTING(__MAC_10_7, __IPHONE_4_3);
      |         ^
1 error generated.