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STATUS_ILLEGAL_FLOAT_CONTEXT
This status belongs to real-mode compatibility and floating-point context handling
STATUS_ILLEGAL_FLOAT_CONTEXT is defined for a real-mode application that issued a floating-point instruction when floating-point hardware is not present. The historical execution context is essential: this is not the generic status for a modern application producing NaN, divide-by-zero, or an invalid floating-point operation.
On supported 32-bit Windows systems, NTVDM provides the environment for DOS and 16-bit Windows applications. Such compatibility execution has different CPU-state and segmented-memory concerns from a native PE process. A dump taken only at the outer NTVDM process can therefore be misleading unless the investigator also records the guest/real-mode program state and the instruction that triggered the event.
Preserve the faulting instruction bytes, guest program identity, emulation/VDM state, and platform architecture. Confirm whether the application expected x87 hardware or an emulator path and whether the same binary has an installation option for non-coprocessor systems. Do not diagnose this as a damaged floating-point data value from the NTSTATUS name alone. On 64-bit Windows, first verify the execution path because Microsoft does not include NTVDM in 64-bit Windows.
What to inspect
- Identify the real-mode/16-bit application and capture the faulting floating-point instruction.
- Check whether the compatibility environment provides the hardware or emulation capability the application expects.
- Distinguish this status from native floating-point exceptions raised by ordinary Win32/Win64 code.
References
- Microsoft: NTVDM and 16-bit app support
- Microsoft: Windows console changes
- Microsoft: Process creation flags
- Microsoft: PE format
- Microsoft Open Specifications: NTSTATUS values
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