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STATUS_WX86_SINGLE_STEP
Microsoft debugger source recognizes this WX86 code as a distinct exception filter
STATUS_WX86_SINGLE_STEP is an informational exception code from the Win32 x86 emulation subsystem. Microsoft's DbgShell source explicitly defines 0x4000001E as STATUS_WX86_SINGLE_STEP and assigns it a dedicated debugger filter name, separate from ordinary STATUS_SINGLE_STEP. That is concrete evidence that debugging tools need to preserve the WX86 code rather than normalize it prematurely to the native processor exception.
Windows debugger documentation explains the general single-step/breakpoint flow: first-chance notification lets the debugger inspect or handle the event before frame-based handlers, and debugger exception settings can break, defer to second chance, notify, or ignore an exception. Those docs describe Windows debugging generally; they do not publish the private x86-emulator transition that raises this WX86 status. Therefore the useful diagnosis is at the emulated thread/debugger boundary, not an invented emulator implementation detail.
Capture the exception code without lossy conversion, thread context, instruction address in the x86 guest view, debugger first/second-chance state, and the action passed when continuing the debug event. Compare with STATUS_WX86_BREAKPOINT: both are recognized separately by Microsoft debugger code. If a debugger handles native single-step but ignores WX86 single-step, stepping can appear to hang or run past the expected boundary even though the emulation subsystem generated a distinct event.
What to inspect
- Preserve the raw WX86 exception code and emulated x86 instruction context.
- Check debugger filter settings and first/second-chance handling for the WX86 code.
- Compare continuation behavior with native STATUS_SINGLE_STEP without merging the two codes.
References
- Microsoft Open Specifications: NTSTATUS values
- Microsoft DbgShell source: WX86 exception filters
- Microsoft: Debugger Exception Handling
- Microsoft: Controlling Exceptions and Events
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