clang -O2  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations unistd/posix_close.c -o unistd/posix_close -D_POSIX_C_SOURCE=202405L  -lm  -lintl
unistd/posix_close.c:5:24: error: use of undeclared identifier 'posix_close'
int (*foo)(int, int) = posix_close;
                       ^
1 error generated.