[Qemu-devel] [Bug 1233225] Re: mips/mipsel linux user float division problem

[Petar Jovanovic]

This is a known issue.
There was a fix proposal by Thomas Schwinge back in June

http://patchwork.ozlabs.org/patch/250161/

but he has not updated the patch per suggestion ever since, though the patch
as is was much closer to correct behaviour than what it is now in the source.

If anyone is in hurry, he/she can pick up that change.

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https://bugs.launchpad.net/bugs/1233225

Title:
  mips/mipsel linux user float division problem

Status in QEMU:
  Confirmed

Bug description:
  Hi,

  I tested the following with the qemu git HEAD as of 2013-09-30 on
  Debian stable and testing. My host runs amd64 but I also tried this
  out inside a i386 chroot with the same result. The problem occurs for
  mips and mipsel. Given the following program:

  #include <stdio.h>
  int main(int argc, char **argv)
  {
      int a = 1;
      double d = a/2.0;
      printf("%f\n", d);
      return 0;
  }

  Instead of printing 0.5, it will print 2.0 if executed in qemu user
  mode.

  $ mipsel-linux-gnu-gcc mipstest.c
  $ ~/qemu/mipsel-linux-user/qemu-mipsel ./a.out
  2.0

  Expecting this to be a problem with my cross compiler (gcc-4.4 from
  emdebian) I ran a fully emulated debian squeeze environment inside
  qemu. There, I compiled the same program natively with gcc and as
  expected got 0.5 as the output. I also copied the cross compiled
  binary inside the emulated environment and also got 0.5 when I ran it.
  So the same mips/mipsel binary produces different output depending on
  whether it is run in a fully emulated environment or qemu user mode.

  Can anybody else reproduce this problem?

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