glibc/sysdeps/i386/bits/setjmp.h

/* Define the machine-dependent type `jmp_buf'.  Intel 386 version.  */

#ifndef _SETJMP_H
# error "Never include <bits/setjmp.h> directly; use <setjmp.h> instead."
#endif

#if defined __USE_MISC || defined _ASM
# define JB_BX	0
# define JB_SI	1
# define JB_DI	2
# define JB_BP	3
# define JB_SP	4
# define JB_PC	5
#endif

#ifndef	_ASM
typedef int __jmp_buf[6];
#endif

/* Test if longjmp to JMPBUF would unwind the frame
   containing a local variable at ADDRESS.  */
#define _JMPBUF_UNWINDS(jmpbuf, address) \
  ((int) (address) < (jmpbuf)[JB_SP])