cc -pthread -Wall -Wextra -Werror=implicit-function-declaration wctype/wctype_l.c -o wctype/wctype_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -liconv wctype/wctype_l.c:13:23: error: call to undeclared function 'wctype_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] 13 | wctype_t charclass = wctype_l("alpha", locale); | ^ wctype/wctype_l.c:13:23: note: did you mean 'wctype'? /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/___wctype.h:190:2: note: 'wctype' declared here 190 | wctype(const char *); | ^ 1 error generated.