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[Qemu-devel] [Bug 1233225] Re: mips/mipsel linux user float division pro
From: |
Stefan Weil |
Subject: |
[Qemu-devel] [Bug 1233225] Re: mips/mipsel linux user float division problem |
Date: |
Tue, 01 Oct 2013 17:51:22 -0000 |
I can confirm that something is strange with MIPS Linux user emulation,
but get a different result (which is also wrong):
# Your test code is in file divtest.c.
$ mipsel-linux-gnu-gcc-4.7 -g -static divtest.c
$ mipsel-linux-user/qemu-mipsel a.out
0.000000
Some more tests:
printf("%f\n", a * 1.0); // 0.000000 = bad
printf("%f\n", (double)a); // 0.000000 = bad
printf("%f\n", 1.0); // 1.000000 = good
Test environment:
* latest QEMU sources + default configure & make on x86_64 Debian squeeze host
* gcc-4.7-mipsel-linux-gnu 4.7.2-5 amd64 GNU C compiler
** Changed in: qemu
Status: New => Confirmed
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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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- [Qemu-devel] [Bug 1233225] Re: mips/mipsel linux user float division problem,
Stefan Weil <=