cc -pthread  -Wall -Wextra duplocale.c -o duplocale -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
duplocale.c:9:2: error: use of undeclared identifier 'locale_t'
        locale_t locale1 = duplocale(LC_GLOBAL_LOCALE);
        ^
duplocale.c:10:19: error: use of undeclared identifier 'locale_t'
        if ( locale1 == (locale_t) 0 )
                         ^
duplocale.c:10:7: error: use of undeclared identifier 'locale1'
        if ( locale1 == (locale_t) 0 )
             ^
duplocale.c:12:2: error: use of undeclared identifier 'locale_t'
        locale_t locale2 = duplocale(locale1);
        ^
duplocale.c:13:19: error: use of undeclared identifier 'locale_t'
        if ( locale2 == (locale_t) 0 )
                         ^
duplocale.c:13:7: error: use of undeclared identifier 'locale2'
        if ( locale2 == (locale_t) 0 )
             ^
duplocale.c:15:2: error: use of undeclared identifier 'locale_t'
        locale_t locale3 = newlocale(LC_ALL_MASK, "C", (locale_t) 0);
        ^
duplocale.c:16:19: error: use of undeclared identifier 'locale_t'
        if ( locale3 == (locale_t) 0 )
                         ^
duplocale.c:16:7: error: use of undeclared identifier 'locale3'
        if ( locale3 == (locale_t) 0 )
             ^
duplocale.c:18:2: error: use of undeclared identifier 'locale_t'
        locale_t locale4 = duplocale(locale3);
        ^
duplocale.c:19:19: error: use of undeclared identifier 'locale_t'
        if ( locale4 == (locale_t) 0 )
                         ^
duplocale.c:19:7: error: use of undeclared identifier 'locale4'
        if ( locale4 == (locale_t) 0 )
             ^
duplocale.c:21:2: error: implicit declaration of function 'freelocale' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        freelocale(locale1);
        ^
duplocale.c:21:2: note: did you mean 'setlocale'?
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/locale.h:53:8: note: 'setlocale' declared here
char            *setlocale(int, const char *);
                 ^
duplocale.c:21:13: error: use of undeclared identifier 'locale1'
        freelocale(locale1);
                   ^
duplocale.c:22:13: error: use of undeclared identifier 'locale2'
        freelocale(locale2);
                   ^
duplocale.c:23:13: error: use of undeclared identifier 'locale3'
        freelocale(locale3);
                   ^
duplocale.c:24:13: error: use of undeclared identifier 'locale4'
        freelocale(locale4);
                   ^
17 errors generated.