cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations ctype/toupper_l.c -o ctype/toupper_l -D_POSIX_C_SOURCE=202405L -lm -lpthread -lrt -lintl -liconv
ctype/toupper_l.c:5:29: error: ‘toupper_l’ undeclared here (not in a function); did you mean ‘toupper’?
    5 | int (*foo)(int, locale_t) = toupper_l;
      |                             ^~~~~~~~~
      |                             toupper