cc -pipe -O -pthread -Wall -Wextra -Werror=implicit-function-declaration locale/getlocalename_l.c -o locale/getlocalename_l -D_GNU_SOURCE -D_BSD_SOURCE -D_ALL_SOURCE -D_DEFAULT_SOURCE -lm -lpthread -lrt -lrt -lcrypt locale/getlocalename_l.c: In function 'main': locale/getlocalename_l.c:9:21: error: implicit declaration of function 'getlocalename_l'; did you mean 'setlocale'? [-Werror=implicit-function-declaration] const char* name = getlocalename_l(LC_COLLATE, LC_GLOBAL_LOCALE); ^~~~~~~~~~~~~~~ setlocale locale/getlocalename_l.c:9:21: warning: initialization of 'const char *' from 'int' makes pointer from integer without a cast [-Wint-conversion] locale/getlocalename_l.c:17:7: warning: assignment to 'const char *' from 'int' makes pointer from integer without a cast [-Wint-conversion] name = getlocalename_l(LC_COLLATE, locale); ^ cc1: some warnings being treated as errors