Problem:
You have C code like
errno = EFAULT;
but when you try to compile it you see an error message like
main.c:4:5: note: each undeclared identifier is reported only once for each function it appears in main.c:4:13: error: ‘EFAULT’ undeclared (first use in this function) errno = EFAULT;
Solution:
Add
#include <errno.h>
at the top of the source file where the error occured. This will include both error codes like EFAULT
and the global errno
variable itself.