GNU bug report logs - #78985
sort-float failure on ppc64, LDBL_MIN fraction part too long for test command to parse

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Message #22 received at 78985 <at> debbugs.gnu.org (full text, mbox):

From: Collin Funk <collin.funk1 <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: 78985 <at> debbugs.gnu.org, "C. Neidahl" <opna2608 <at> protonmail.com>
Subject: Re: bug#78985: sort-float failure on ppc64, LDBL_MIN fraction part
 too long for test command to parse
Date: Fri, 11 Jul 2025 20:59:43 -0700

Collin Funk <collin.funk1 <at> gmail.com> writes:

>> Oh, right. Thanks. I installed the attached further patch to fix that.
>> This is cleaner anyway.
>
> This test still fails on cfarm110 for me, logs attached.
>
> I was looking at it the other day, but was unable to get a working
> version.
>
> I'll see if I have any ideas later.

I think I see the issue now. Using this test program:

    $ cat main.c 
    #include <stdio.h>
    int
    main (void)
    {
      long double a = 2.225073858507201383090232717332e-308;
      long double b = 2.2250738585072014e-308;
      printf ("a < b:   %d\n", a < b);
      printf ("a > b:   %d\n", a > b);
      printf ("a == b:  %d\n", a == b);
      return 0;
    }
    $ gcc main.c
    $ ./a.out
    a < b:   0
    a > b:   0
    a == b:  1

And then in gdb we can see strtold returns equal numbers:

    Breakpoint 1, general_numcompare (sa=0x10051460 "2.225073858507201383090232717332e-308", sb=0x10051486 "2.2250738585072014e-308") at src/sort.c:2032
    2032	  long double a = strtold (sa, &ea);
    Missing separate debuginfos, use: debuginfo-install glibc-2.17-326.el7_9.3.ppc64
    (gdb) n
    2033	  long double b = strtold (sb, &eb);
    (gdb) n
    2036	  if (sa == ea)
    (gdb) print a
    $1 = 2.2250738585072013830902327173324041e-308
    (gdb) print b
    $2 = 2.2250738585072013830902327173324041e-308
    (gdb) print a == b
    $3 = 1

Maybe a solution would be to compare the strings instead of calling
strold? I guess that would make life harder though...

Collin

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