New subject: [Bug 60230] Microsoft Windows Floating Point Application crashes when testing exceptions

Aug. 24, 2026

      http://bugs.winehq.org/show_bug.cgi?id=60230

            Bug ID: 60230
           Summary: Microsoft Windows Floating Point Application crashes
                    when testing exceptions
           Product: Wine
           Version: 11.16
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: -unknown
          Assignee: wine-bugs@list.winehq.org
          Reporter: alexhenrie24@gmail.com
  Target Milestone: ---
      Distribution: ---

In the Windows 3.1 era, Microsoft developed a program known as either
"WinFloat" or "FloatApp" to help programmers verify that floating-point
exception handling worked correctly on their computers. I learned about it from
the fascinating article at https://www.os2museum.com/wp/failing-to-fail/ -
which even has screenshots! And the program comes with a WINFLOAT.HLP file
which has lots of documentation about win87em.dll!

Unfortunately, FloatApp doesn't work quite right on Wine. To reproduce the
problem:

1. Copy winfloat.exe to an otherwise empty directory

2. Run `unzip winfloat.exe` (yes, I know it's an installer, but unzipping it is
easier than running it in DOSBox)

3. Run `wine FLOATAPP.EXE`

4. Click the Exceptions menu, and under "App" or "DLL" click "Divide by Zero",
"Overflow", "Underflow", or "Invalid"

On my real 486 that runs Windows 95, clicking "Divide by Zero" causes a message
box to appear that says "Application signal handler detected ZERODIVIDE
exception." Clicking "Overflow" causes a message box to appear that says
"Application signal handler detected OVERFLOW exception." Interestingly,
clicking "Underflow" or "Invalid" does nothing on that PC. The main window says
that the 8087 control word is 0x1370 and the Win87Em control word is 0x1332. It
makes sense that Underflow wouldn't work because the Underflow mask bit (bit 4)
is set in both control words. But the Invalid mask bit (bit 0) is not set in
either control word, so I don't know why I'm not getting any Invalid
exceptions.

On Wine, clicking any of the exceptions in the menu causes the program to
crash. The main window says that the 8087 control word is 0x027f and the
Win87Em control word is 0x1320.

$ sha256sum winfloat.exe
0ddda79599c01664d3f1b8004016f5cf837d2b6f11a25f23eec2e596d96a4cc7

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[Bug 60230] New: Microsoft Windows Floating Point Application crashes when testing exceptions

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