1#ifndef _ERRNO_H
2#include <stdlib/errno.h>
3#if !defined _ISOMAC && !defined __ASSEMBLER__
4
5# if IS_IN (rtld)
6# include <dl-sysdep.h>
7# ifndef RTLD_PRIVATE_ERRNO
8# error "dl-sysdep.h must define RTLD_PRIVATE_ERRNO!"
9# endif
10# else
11# define RTLD_PRIVATE_ERRNO 0
12# endif
13
14# if RTLD_PRIVATE_ERRNO
15/* The dynamic linker uses its own private errno variable.
16 All access to errno inside the dynamic linker is serialized,
17 so a single (hidden) global variable is all it needs. */
18
19# undef errno
20# define errno rtld_errno
21extern int rtld_errno attribute_hidden;
22
23# elif IS_IN_LIB && !IS_IN (rtld)
24
25# undef errno
26# if IS_IN (libc)
27# define errno __libc_errno
28# else
29# define errno errno /* For #ifndef errno tests. */
30# endif
31extern __thread int errno attribute_tls_model_ie;
32
33# endif /* IS_IN_LIB */
34
35# define __set_errno(val) (errno = (val))
36
37extern int *__errno_location (void) __THROW __attribute_const__
38# if RTLD_PRIVATE_ERRNO
39 attribute_hidden
40# endif
41;
42libc_hidden_proto (__errno_location)
43
44#endif /* !_ISOMAC && !__ASSEMBLER__ */
45#endif /* !_ERRNO_H */
46

source code of glibc/include/errno.h