ripped from Debian

 this change was made to generic __nexttowardf, but not the long double version

 2008-05-05  Aurelien Jarno  <aurelien@aurel32.net>

 	* sysdeps/ieee754/ldbl-128/s_nexttowardf.c: Include float.h.

 	(__nexttowardf): Use math_opt_barrier and

 	math_force_eval macros.  If FLT_EVAL_METHOD is not 0, force

 	x to float using asm.

  sysdeps/ieee754/ldbl-128/s_nexttowardf.c |   26 ++++++++++++++++----------

  1 file changed, 16 insertions(+), 10 deletions(-)

 diff -durN glibc-2.10.1.orig/sysdeps/ieee754/ldbl-128/s_nexttowardf.c glibc-2.10.1/sysdeps/ieee754/ldbl-128/s_nexttowardf.c

 --- glibc-2.10.1.orig/sysdeps/ieee754/ldbl-128/s_nexttowardf.c	1999-07-14 02:09:42.000000000 +0200

 +++ glibc-2.10.1/sysdeps/ieee754/ldbl-128/s_nexttowardf.c	2009-11-13 00:50:06.000000000 +0100

 @@ -19,7 +19,8 @@

  #endif

  #include "math.h"

 -#include "math_private.h"

 +#include <math_private.h>

 +#include <float.h>

  #ifdef __STDC__

  	float __nexttowardf(float x, long double y)

 @@ -44,10 +45,12 @@

  	   return x+y;

  	if((long double) x==y) return y;	/* x=y, return y */

  	if(ix==0) {				/* x == 0 */

 -	    float x2;

 +	    float u;

  	    SET_FLOAT_WORD(x,(u_int32_t)((hy>>32)&0x80000000)|1);/* return +-minsub*/

 -	    x2 = x*x;

 -	    if(x2==x) return x2; else return x;	/* raise underflow flag */

 +	    u = math_opt_barrier (x);

 +	    u = u * u;

 +	    math_force_eval (u);		/* raise underflow flag */

 +	    return x;

  	}

  	if(hx>=0) {				/* x > 0 */

  	    if(hy<0||(ix>>23)>(iy>>48)-0x3f80

 @@ -67,13 +70,16 @@

  	    }

  	}

  	hy = hx&0x7f800000;

 -	if(hy>=0x7f800000) return x+x;	/* overflow  */

 +	if(hy>=0x7f800000) {

 +	  x = x+x;	/* overflow  */

 +	  if (FLT_EVAL_METHOD != 0)

 +	    /* Force conversion to float.  */

 +	    asm ("" : "+m"(x));

 +	  return x;

 +	}

  	if(hy<0x00800000) {		/* underflow */

 -	    float x2 = x*x;

 -	    if(x2!=x) {		/* raise underflow flag */

 -	        SET_FLOAT_WORD(x2,hx);

 -		return x2;

 -	    }

 +	    float u = x*x;

 +	    math_force_eval (u);	/* raise underflow flag */

  	}

  	SET_FLOAT_WORD(x,hx);

  	return x;