Date: Sun, 24 Jan 1999 10:22:07 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: DJ Delorie <dj AT delorie DOT com>
cc: djgpp-workers AT delorie DOT com, Robert Hoehne <robert DOT hoehne AT gmx DOT net>
Subject: Re: Bug when printing long doubles
In-Reply-To: <Pine.LNX.3.93.990120112136.2655A-100000@acp3bf>
Message-ID: <Pine.SUN.3.91.990124102120.4501C-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Reply-To: djgpp-workers AT delorie DOT com


Here's a patch for doprnt.c that takes care of printing unnormals.  I
don't think we've agreed on what exactly to print; the patch below
prints "Unnormal" (with a sign, if necessary), but you can change that
by modifying a single string that gets assigned to UNNORMAL_REP[].

*** src/libc/ansi/stdio/doprnt.c~1	Fri Jan 15 14:31:58 1999
--- src/libc/ansi/stdio/doprnt.c	Sat Jan 23 20:39:22 1999
*************** static int isspeciall(long double d, cha
*** 71,76 ****
--- 71,77 ----
  #endif
  
  static char NULL_REP[] = "(null)";
+ static char UNNORMAL_REP[] = "Unnormal";
  
  int
  _doprnt(const char *fmt0, va_list argp, FILE *fp)
*************** cvtl(long double number, int prec, int f
*** 549,556 ****
    /*
     * get integer portion of number; put into the end of the buffer; the
     * .01 is added for modf(356.0 / 10, &integer) returning .59999999...
     */
!   for (; integer; ++expcnt)
    {
      tmp = modfl(integer * 0.1L , &integer);
      *p-- = tochar((int)((tmp + .01L) * 10));
--- 550,560 ----
    /*
     * get integer portion of number; put into the end of the buffer; the
     * .01 is added for modf(356.0 / 10, &integer) returning .59999999...
+    * The test p >= startp is due to paranoia: buffer length is guaranteed
+    * to be large enough, but if tmp is somehow a NaN, this loop could
+    * eventually blow away the stack.
     */
!   for (; integer && p >= startp; ++expcnt)
    {
      tmp = modfl(integer * 0.1L , &integer);
      *p-- = tochar((int)((tmp + .01L) * 10));
*************** isspeciall(long double d, char *bufp)
*** 863,868 ****
--- 867,882 ----
    } *ip = (struct IEEExp *)&d;
  
    nan = 0;  /* don't assume the static is 0 (emacs) */
+ 
+   /* Unnormals: the MSB of mantissa is non-zero, but the exponent is
+      not zero either.  */
+   if ((ip->manh & 0x80000000U) == 0 && ip->exp != 0)
+   {
+     if (ip->sign)
+       *bufp++ = '-';
+     strcpy(bufp, UNNORMAL_REP);
+     return strlen(bufp) + ip->sign;
+   }
    if (ip->exp != 0x7fff)
      return(0);
    if ((ip->manh & 0x7fffffff) || ip->manl)