#include <errno.h>

#include <cerrno>

　extern int errno;

extern int errno;

extern int *__errno_location (void) __THROW __attribute__ ((__const__));
#define errno (*__errno_location ())

__errno_location (void)
{
  return &errno;
}

__thread int errno;

_CRTIMP extern int * __cdecl _errno(void);
#define errno   (*_errno())

int * __error(void);
#define errno (* __error())

extern int errno;
__weak_reference(__error_unthreaded, __error);
int *
__error_unthreaded(void)
{
    return(&errno);
}

int errno;

#undef errno
extern  int     errno;
int *
__error(void)
{
    struct pthread *curthread;
    if (_thr_initial != NULL) {
        curthread = _get_curthread();
        if (curthread != NULL && curthread != _thr_initial)
            return (&curthread->error);
    }
    return (&errno);
}

extern volatile int*   __errno(void);
#define  errno   (*__errno())

volatile int*  __errno( void )
{
  return  &((volatile int*)__get_tls())[TLS_SLOT_ERRNO];
}

enum {
  TLS_SLOT_SELF = 0, /* The kernel requires this specific slot for x86. */
  TLS_SLOT_THREAD_ID,
  TLS_SLOT_ERRNO,
(コメント略)
  TLS_SLOT_OPENGL_API = 3,
(以下略)

# define __get_tls() \
    ({ register unsigned int __val; \
       asm ("mrc p15, 0, %0, c13, c0, 3" : "=r"(__val)); \
       (volatile void*) __val; })

#      define __get_tls() ( *((volatile void **) 0xffff0ff0) )