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From: "guojiufu at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug libc/13524] New: glibc 32: sscanf get wrong result for long double at  4e-28 and 8e-28 at Linux on Power
Date: Wed, 21 Dec 2011 02:58:00 -0000
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http://sourceware.org/bugzilla/show_bug.cgi?id=13524

             Bug #: 13524
           Summary: glibc 32: sscanf get wrong result for long double at
                    4e-28 and 8e-28 at Linux on Power
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper.fsp@gmail.com
        ReportedBy: guojiufu@gmail.com
    Classification: Unclassified


Hardware >POWER5+ 
software 
---
#include<stdio.h>
#include<math.h>

union U { long double ld; int d[sizeof(long double)/sizeof(int)];};
void Print(long double data) {
  union U u;
  u.ld=data;
  printf("long double:%Lg\t hex:" ,u.ld);
  int i;
  for(i = 0; i < sizeof(long double)/sizeof(int);++i) printf("%0x ",u.d[i]);
  printf("\n");
}

void foo(char * str,long double b){
  long double a ;
  (void)sscanf(str, "%Le", &a);
  Print(b);
  Print(a);
  Print(a-b);
}

int main()
{
  foo("4e-28L",+4e-28L);
  foo("8e-28L",+8e-28L);
  return 0 ;
}
-----------
gcc t.c -m32;./a.out 
long double:4e-28        hex:3a3fb0f6 be506019 36d06c5e 54eb70c4
long double:4e-28        hex:3a3fb0f6 be506019 36d06c5e 54eb70e4
long double:7.96546e-59  hex:33e00000 0 0 0
long double:8e-28        hex:3a4fb0f6 be506019 36e06c5e 54eb70c4
long double:8e-28        hex:3a4fb0f6 be506019 36e06c5e 54eb70d4
long double:7.96546e-59  hex:33e00000 0 0 0
--
gcc t.c -m64;./a.out 
long double:4e-28        hex:3a3fb0f6 be506019 36d06c5e 54eb70c4
long double:4e-28        hex:3a3fb0f6 be506019 36d06c5e 54eb70c4
long double:0    hex:0 0 0 0
long double:8e-28        hex:3a4fb0f6 be506019 36e06c5e 54eb70c4
long double:8e-28        hex:3a4fb0f6 be506019 36e06c5e 54eb70c4
long double:0    hex:0 0 0 0
--

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