cc -pthread -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations ctype/islower_l.c -o ctype/islower_l -D_POSIX_C_SOURCE=202405L -lm -lpthread -liconv ctype/islower_l.c:5:17: error: type specifier missing, defaults to 'int' [-Werror,-Wimplicit-int] int (*foo)(int, locale_t) = islower_l; ^ ctype/islower_l.c:5:29: error: use of undeclared identifier 'islower_l'; did you mean 'islower'? int (*foo)(int, locale_t) = islower_l; ^~~~~~~~~ islower /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/_ctype.h:249:1: note: 'islower' declared here islower(int _c) ^ ctype/islower_l.c:5:7: error: incompatible function pointer types initializing 'int (*)(int, int)' with an expression of type 'int (int)' [-Werror,-Wincompatible-function-pointer-types] int (*foo)(int, locale_t) = islower_l; ^ ~~~~~~~~~ 3 errors generated.