other/4894: gcc/config/float-i386.h bad define?

other/4894: gcc/config/float-i386.h bad define?

[nzook]

>Number:         4894
>Category:       other
>Synopsis:       gcc/config/float-i386.h bad define?
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Sun Nov 18 18:36:00 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     nzook@bga.com
>Release:        gcc-3.0.1
>Organization:
>Environment:
i*86
>Description:
from ${SRCDIR}/gcc/config/float-i386.h:

#if __STDC_VERSION__ >= 199901L

...

   /* Number of decimal digits to enable rounding to the given number of
      decimal digits without loss of precision.
         if FLT_RADIX == 10^n:  #mantissa * log10 (FLT_RADIX)
         else                :  ceil (1 + #mantissa * log10 (FLT_RADIX))
      where #mantissa is the number of bits in the mantissa of the widest
      supported floating-point type.
   */
# undef DECIMAL_DIG
# define DECIMAL_DIG	21

#endif	/* C99 */
>How-To-Repeat:

>Fix:
I don't care what the C standard says, NO x87 processor has ever supported more than 64 mantissas bits in an external format.  Internal fromats have usually been 66 bits.  (K7 is 68).

This redefinition is WRONG.  It should be dropped before something breaks.
>Release-Note:
>Audit-Trail:
>Unformatted:

Re: other/4894: gcc/config/float-i386.h bad define?

[rth]

The following reply was made to PR other/4894; it has been noted by GNATS.

From: rth@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
  nobody@gcc.gnu.org, nzook@bga.com
Cc:  
Subject: Re: other/4894: gcc/config/float-i386.h bad define?
Date: 27 Nov 2001 05:15:00 -0000

 Synopsis: gcc/config/float-i386.h bad define?
 
 State-Changed-From-To: open->closed
 State-Changed-By: rth
 State-Changed-When: Mon Nov 26 21:15:00 2001
 State-Changed-Why:
     Not a bug.  See ISO/IEC 9899:1999 Section 5.2.4.2.2 paragraph 8.
     
        ceil (1 + 64 * log10(2))
      = ceil (1 + 64 * .30102999566398119521)
      = ceil (1 + 19.26591972249479649344)
      = ceil (20.26591972249479649344)
      = 21
     
     QED.
 
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&pr=4894&database=gcc

Re: other/4894: gcc/config/float-i386.h bad define?

[rth]

Synopsis: gcc/config/float-i386.h bad define?

State-Changed-From-To: open->closed
State-Changed-By: rth
State-Changed-When: Mon Nov 26 21:15:00 2001
State-Changed-Why:
    Not a bug.  See ISO/IEC 9899:1999 Section 5.2.4.2.2 paragraph 8.
    
       ceil (1 + 64 * log10(2))
     = ceil (1 + 64 * .30102999566398119521)
     = ceil (1 + 19.26591972249479649344)
     = ceil (20.26591972249479649344)
     = 21
    
    QED.

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