cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations locale/duplocale.c -o locale/duplocale -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
locale/duplocale.c:5:12: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
    5 | locale_t (*foo)(locale_t) = duplocale;
      |            ^
      |           int
locale/duplocale.c:5:1: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
    5 | locale_t (*foo)(locale_t) = duplocale;
      | ^
      | int
locale/duplocale.c:5:17: error: a parameter list without types is only allowed in a function definition
    5 | locale_t (*foo)(locale_t) = duplocale;
      |                 ^
locale/duplocale.c:5:29: error: use of undeclared identifier 'duplocale'; did you mean 'setlocale'?
    5 | locale_t (*foo)(locale_t) = duplocale;
      |                             ^~~~~~~~~
      |                             setlocale
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/locale.h:53:8: note: 'setlocale' declared here
   53 | char            *setlocale(int, const char *);
      |                  ^
4 errors generated.