cc -pthread  -Wall -Wextra -Werror=implicit-function-declaration string/strxfrm_l.c -o string/strxfrm_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
string/strxfrm_l.c:17:7: error: call to undeclared function 'strxfrm_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   17 |         if ( strxfrm_l(A, a, sizeof(A), locale) != 7 )
      |              ^
string/strxfrm_l.c:17:7: note: did you mean 'strxfrm'?
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_string.h:112:9: note: 'strxfrm' declared here
  112 | size_t   strxfrm(char *_LIBC_COUNT(__n) __s1, const char *__s2, size_t __n);
      |          ^
string/strxfrm_l.c:22:13: error: call to undeclared function 'strcoll_l'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
   22 |         int coll = strcoll_l(a, b, locale);
      |                    ^
string/strxfrm_l.c:22:13: note: did you mean 'strcoll'?
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_string.h:90:6: note: 'strcoll' declared here
   90 | int      strcoll(const char *__s1, const char *__s2);
      |          ^
2 errors generated.