cc -pthread  -Wall -Wextra uselocale.c -o uselocale -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm -lpthread  -liconv
uselocale.c:9:2: error: use of undeclared identifier 'locale_t'
        locale_t locale = newlocale(LC_ALL_MASK, "C", (locale_t) 0);
        ^
uselocale.c:10:18: error: use of undeclared identifier 'locale_t'
        if ( locale == (locale_t) 0 )
                        ^
uselocale.c:10:7: error: use of undeclared identifier 'locale'
        if ( locale == (locale_t) 0 )
             ^
uselocale.c:12:2: error: use of undeclared identifier 'locale_t'
        locale_t old_locale = uselocale(locale);
        ^
uselocale.c:13:7: error: use of undeclared identifier 'old_locale'
        if ( old_locale != LC_GLOBAL_LOCALE )
             ^
uselocale.c:13:21: error: use of undeclared identifier 'LC_GLOBAL_LOCALE'
        if ( old_locale != LC_GLOBAL_LOCALE )
                           ^
uselocale.c:15:2: error: use of undeclared identifier 'old_locale'
        old_locale = uselocale((locale_t) 0);
        ^
uselocale.c:15:15: error: implicit declaration of function 'uselocale' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        old_locale = uselocale((locale_t) 0);
                     ^
uselocale.c:15:15: 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 *);
                 ^
uselocale.c:15:26: error: use of undeclared identifier 'locale_t'
        old_locale = uselocale((locale_t) 0);
                                ^
uselocale.c:16:7: error: use of undeclared identifier 'old_locale'
        if ( old_locale != locale )
             ^
uselocale.c:16:21: error: use of undeclared identifier 'locale'
        if ( old_locale != locale )
                           ^
11 errors generated.