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From: "dilyan.palauzov at aegee dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/113679] New: long long minus double with gcc -m32 produces
 different results than other compilers or gcc -m64
Date: Wed, 31 Jan 2024 08:40:21 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 13.2.1
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: dilyan.palauzov at aegee dot org
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X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113679

            Bug ID: 113679
           Summary: long long minus double with gcc -m32 produces
                    different results than other compilers or gcc -m64
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dilyan.palauzov at aegee dot org
  Target Milestone: ---

diff.c is:

#include <stdio.h>
int main(void) {
  long long l =3D 9223372036854775806;
  double d =3D 9223372036854775808.0;
  printf("%f\n", (double)l - d);
  return 0;
}


With gcc (GCC) 13.2.1 20231205 (Red Hat 13.2.1-6), gcc (Ubuntu
9.4.0-1ubuntu1~20.04.2) 9.4.0, clang 16.0.4 and clang 17.0.5:

$ gcc -m64 -o diff diff.c && ./diff
0.000000
$ gcc -m32 -o diff diff.c && ./diff
-2.000000
$ clang -m64 -o diff diff.c && ./diff
0.000000
$ clang -m32 -o diff diff.c && ./diff
0.000000

With cl.exe 19.29.3015319.29.30153 (first is x84 - 32 bit, second is 64 bit)
C:\> CALL "C:\Program Files (x86)\Microsoft Visual
Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" x86 10.0.17763.0
C:\> cl diff.c >nul 2>nul & .\diff.exe
0.000000

C:\> CALL "C:\Program Files (x86)\Microsoft Visual
Studio\2019\Community\VC\Auxiliary\Build\vcvarsall.bat" amd64 10.0.17763.0
C:\> cl diff.c >nul 2>nul & .\diff.exe
0.000000

gcc -m32 produces a different result, compared to gcc -m64, clang 17 (32 and
64bit), and MSCV Visual Studio 2019 (32 and 64bit).=