cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration ctype/isalpha_l.c -o ctype/isalpha_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
ctype/isalpha_l.c:15:8: error: call to undeclared function 'isalpha_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   15 |         if ( !isalpha_l(c1, locale) )
      |               ^
ctype/isalpha_l.c:15:8: note: did you mean 'isalpha'?
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_ctype.h:223:1: note: 'isalpha' declared here
  223 | isalpha(int _c)
      | ^
1 error generated.