clang -O2  -Wall -Wextra uselocale.c -o uselocale -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
uselocale.c:12:24: warning: implicit declaration of function 'uselocale' is invalid in C99 [-Wimplicit-function-declaration]
        locale_t old_locale = uselocale(locale);
                              ^
uselocale.c:12:11: warning: incompatible integer to pointer conversion initializing 'locale_t' (aka 'struct _locale *') with an expression of type 'int' [-Wint-conversion]
        locale_t old_locale = uselocale(locale);
                 ^            ~~~~~~~~~~~~~~~~~
uselocale.c:15:13: warning: incompatible integer to pointer conversion assigning to 'locale_t' (aka 'struct _locale *') from 'int' [-Wint-conversion]
        old_locale = uselocale((locale_t) 0);
                   ^ ~~~~~~~~~~~~~~~~~~~~~~~
3 warnings generated.
../out/minix/basic/uselocale.o: In function `main':
uselocale.c:(.text+0x31d): undefined reference to `uselocale'
uselocale.c:(.text+0x332): undefined reference to `uselocale'
clang: error: linker command failed with exit code 1 (use -v to see invocation)