[Bug libc/3673] New: strtod exponent limit calculations broken

[Bug libc/3673] New: strtod exponent limit calculations broken

[jsm28 at gcc dot gnu dot org]

The strtod exponent limit calculations

          /* Get the exponent limit. */
          if (base == 16)
            exp_limit = (exp_negative ?
                         -MIN_EXP + MANT_DIG + 4 * int_no :
                         MAX_EXP - 4 * int_no + lead_zero);
          else
            exp_limit = (exp_negative ?
                         -MIN_10_EXP + MANT_DIG + int_no :
                         MAX_10_EXP - int_no + lead_zero);

have a few bugs:

* The max exponent calculation for decimals has an off-by-one error.

* The max exponent calculation for hex numbers has an off-by-three error.

* The hex calculation should use 4 * lead_zero not plain lead_zero.

(I haven't checked in detail whether the calculations for minimum exponent are
correct or not.)

This test illustrates the three problems above.  Each line of output should show
two equal numbers, but instead it says

1e+308 inf
8.98847e+307 inf
1.12356e+307 inf

because of wrong detection of overflow that wasn't there.

#include <stdio.h>
#include <stdlib.h>
int
main(void)
{
  printf("%g %g\n", atof("1e308"), atof("100000000e300"));
  printf("%g %g\n", atof("0x1p1023"), atof("0x1000p1011"));
  printf("%g %g\n", atof("0x1p1020"), atof("0x0.00001p1040"));
  return 0;
}

-- 
           Summary: strtod exponent limit calculations broken
           Product: glibc
           Version: 2.4
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: jsm28 at gcc dot gnu dot org
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=3673

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[Bug libc/3673] strtod exponent limit calculations broken

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2006-12-10 01:11 -------
Fixed in cvs.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=3673

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[Bug libc/3673] strtod exponent limit calculations broken

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2007-01-12 18:07 -------
Subject: Bug 3673

CVSROOT:	/cvs/glibc
Module name:	libc
Branch: 	glibc-2_5-branch
Changes by:	jakub@sourceware.org	2007-01-12 18:07:19

Modified files:
	.              : ChangeLog 
	stdlib         : Makefile strtod_l.c 
Added files:
	stdlib         : tst-atof1.c tst-atof2.c tst-strtod2.c 
	                 tst-strtod3.c 

Log message:
	* stdlib/Makefile (tst-strtod3-ENV): Define.
	
	* stdlib/strtod_l.c (____STRTOF_INTERNAL): Parse thousand
	separators also if no non-zero digits found.
	* stdlib/Makefile (tests): Add tst-strtod3.
	
	[BZ #3664]
	* stdlib/strtod_l.c (____STRTOF_INTERNAL): Fix test to recognize
	empty parsed strings.
	* stdlib/Makefile (tests): Add tst-strtod2.
	* stdlib/tst-strtod2.c: New file.
	
	[BZ #3673]
	* stdlib/strtod_l.c (____STRTOF_INTERNAL): Fix exp_limit
	computation.
	* stdlib/Makefile (tests): Add tst-atof2.
	* stdlib/tst-atof2.c: New file.
	
	[BZ #3674]
	* stdlib/strtod_l.c (____STRTOF_INTERNAL): Adjust exponent value
	correctly if removing trailing zero of hex-float.
	* stdlib/Makefile (tests): Add tst-atof1.
	* stdlib/tst-atof1.c: New file.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/ChangeLog.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.10362.2.28&r2=1.10362.2.29
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/tst-atof1.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=NONE&r2=1.1.4.1
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/tst-atof2.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=NONE&r2=1.1.4.1
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/tst-strtod2.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=NONE&r2=1.3.2.1
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/tst-strtod3.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=NONE&r2=1.1.4.1
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/Makefile.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.109.2.2&r2=1.109.2.3
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdlib/strtod_l.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.14&r2=1.14.2.1



-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=3673

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