clang -O2  -Wall -Wextra -Werror=implicit-function-declaration strings/strcasecmp_l.c -o strings/strcasecmp_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE  -lm  -lintl
strings/strcasecmp_l.c:13:7: error: implicit declaration of function 'strcasecmp_l' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        if ( strcasecmp_l("foo", "FOO", locale) != 0 )
             ^
strings/strcasecmp_l.c:13:7: note: did you mean 'strcasecmp'?
/usr/include/strings.h:63:6: note: 'strcasecmp' declared here
int      strcasecmp(const char *, const char *);
         ^
1 error generated.