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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/113204] lto1: error: qsort comparator non-negative on
 sorted output: 64
Date: Mon, 08 Jan 2024 14:40:11 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113204

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
it's really odd, I don't see how it could fail.  The only suspicious bit is

  int file_order1 =3D n1->lto_file_data ? n1->lto_file_data->order : -1;
  int file_order2 =3D n2->lto_file_data ? n2->lto_file_data->order : -1;

  /* Order files same way as they appeared in the command line to reduce
     seeking while copying sections.  */
  if (file_order1 !=3D file_order2)
    return file_order1 - file_order2;

the non-presence of n{1,2}->lto_file_data represented as -1 makes whether
non-presence is first dependent on the value of the order of the other.

Maybe explicitly spelling that out would be better.

  if (file_order1 !=3D file_order2)
    {
      if (file_order1 =3D=3D -1)
        return -1;
      if (file_order2 =3D=3D -1)
        return 1;
      return file_order1 - file_order2;
    }

or so.=