Why Clang compiler complains although all includes are presented - c

Question

I'm trying to work through XDP tutorial and having issue with samples compilation. Why clang complains regarding includes that are already done?
Example:
common_params.c:105:4: warning: incompatible implicit declaration of built-in function ‘strncpy’
common_params.c:105:4: note: include ‘<string.h>’ or provide a declaration of ‘strncpy’
common_params.c:110:6: error: ‘errno’ undeclared (first use in this function)
110 | errno, strerror(errno));
| ^~~~~
common_params.c:15:1: note: ‘errno’ is defined in header ‘<errno.h>’; did you forget to ‘#include <errno.h>’?
14 | #include "common_params.h"
+++ |+#include <errno.h>
Cheching common_params.c shoes it already have string.h and errno.h included:
# head ../common/common_params.c
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <getopt.h>
#include <errno.h>
#include <stdio.h>
Files are presented in the box:
# ls -l /usr/include/errno.h
-rw-r--r-- 1 root root 23 Jun 6 18:36 /usr/include/errno.h
# ls -l /usr/include/string.h
-rw-r--r-- 1 root root 238 Jun 6 18:36 /usr/include/string.h
# cat /usr/include/errno.h
#include <asm/errno.h>
# cat /usr/include/asm/errno.h
#include <asm-generic/errno.h>
# head /usr/include/asm-generic/errno.h
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _ASM_GENERIC_ERRNO_H
#define _ASM_GENERIC_ERRNO_H
#include <asm-generic/errno-base.h>
#define EDEADLK 35 /* Resource deadlock would occur */
#define ENAMETOOLONG 36 /* File name too long */
#define ENOLCK 37 /* No record locks available */