Home/ Questions/Q 8906247
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T02:36:15+00:00

This has been puzzling me for the last several days! We have an application

  • 0

This has been puzzling me for the last several days!

We have an application where we’re running into a divide-by-zero. That application is purposely built to raise exceptions in such cases, with a call to the _controlfp_s function to change the masks on floating point exceptions.

Now, when running into a divide-by-zero on pretty much all of our machines, Visual Studio 2005 debugger breaks at the proper location within our source files. However, on 1 machine, the break location is all over the place and appears to be irrelevant to the actual cause of the break. So as a test, I built a simple C win32 program with just the following lines of code:

int main(int argc, char *argv[])
{
    float temp1, temp2, temp3;
    unsigned int control;

    _controlfp_s(&control, (_EM_UNDERFLOW + _EM_INEXACT, _MCW_EM);

    temp1=1.0;
    temp2=0.0;
    temp3=temp1/temp2;

    return 0;
}

On all those “good” machines, the code does break at temp3. However, on the bad machine, the code breaks at:

C:\Program Files (x86)\Microsoft Visual Studio 8\VC\crt\src\tidtable.c

function:

__set_flsgetvalue()

Looking at the registers as I step through the assembly code, everything looks fine until I hit the “fstp” instruction… then all the registers seem to be messed up (vs looking as expected on a good machine). When comparing the stack on the good vs bad, I also see stack entries on the bad machine, which I don’t see on the good one…

I’m skipping quite a few details here in an attempt to keep this first pass short… but I’ll add up more if someone is so kind as to try to help.

Notes:
OS Win7 x64, running all the latest VS2005 Service Packs. Compared to a similar (working) machine running same software and service packs. Getting same weird behavior when running on VS2010.

Thanks in advance.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Wow!

    After showing this post to a friend… he found an intel document showing very similar symptoms about some of their cpu’s… I then found the exact document that applied to our specific CPU (intel i5-2500) here:

    http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/2nd-gen-core-deskt…

    See errata BJ1

    This pretty much exactly describes what I’m running into! I never (seriously) thought it would be an issue at THAT level!

    • 0