_ansi.h

标准c库代码,可以应用于各个系统提供了大量的基本函数

/* Provide support for both ANSI and non-ANSI environments.  */

/* Some ANSI environments are "broken" in the sense that __STDC__ cannot be
   relied upon to have it's intended meaning.  Therefore we must use our own
   concoction: _HAVE_STDC.  Always use _HAVE_STDC instead of __STDC__ in newlib
   sources!

   To get a strict ANSI C environment, define macro _STRICT_ANSI.  This will
   "comment out" the non-ANSI parts of the ANSI header files (non-ANSI header
   files aren't affected).  */

#ifndef	_ANSIDECL_H_
#define	_ANSIDECL_H_

#include <sys/config.h>

/* First try to figure out whether we really are in an ANSI C environment.  */
/* FIXME: This probably needs some work.  Perhaps sys/config.h can be
   prevailed upon to give us a clue.  */

#if __STDC__ == 1
#define _HAVE_STDC
#endif

#ifdef _HAVE_STDC
#define	_PTR		void *
#define	_AND		,
#define	_NOARGS		void
#define	_CONST		const
#define	_VOLATILE	volatile
#define	_SIGNED		signed
#define	_DOTS		, ...
#define _VOID void
#define	_EXFUN(name, proto)		name proto
#define	_DEFUN(name, arglist, args)	name(args)
#define	_DEFUN_VOID(name)		name(_NOARGS)
#define _CAST_VOID (void)
#ifndef _LONG_DOUBLE
#define _LONG_DOUBLE long double
#endif
#ifndef _PARAMS
#define _PARAMS(paramlist)		paramlist
#endif
#else	
#define	_PTR		char *
#define	_AND		;
#define	_NOARGS
#define	_CONST
#define	_VOLATILE
#define	_SIGNED
#define	_DOTS
#define _VOID void
#define	_EXFUN(name, proto)		name()
#define	_DEFUN(name, arglist, args)	name arglist args;
#define	_DEFUN_VOID(name)		name()
#define _CAST_VOID
#define _LONG_DOUBLE double
#ifndef _PARAMS
#define _PARAMS(paramlist)		()
#endif
#endif

/* Support gcc's __attribute__ facility.  */

#ifdef __GNUC__
#define _ATTRIBUTE(attrs) __attribute__ (attrs)
#else
#define _ATTRIBUTE(attrs)
#endif

#endif /* _ANSIDECL_H_ */