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Editorial Team
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Asked: 2026-05-11T18:26:14+00:00

I have an app which uses a keyboard hook procedure in a library. The

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I have an app which uses a keyboard hook procedure in a library. The wParam in the hook for one message is 255 which we think is “(reserved / OEMClear)”. I’d like to work out the source of this message as it causes my application to crash in the library, and given it shouldn’t be happening it would be good to identify it. The message comes in repeatedly on only one PC we have – other computers don’t see the message at all.

So, is there a way to trace the source of a message sent to a window please, or all those on the system?

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1 Answer

  1. Editorial Team

    There is no built-in way to find out who sent the window message, not even win32k keeps track of this; you might be able to find it out with a kernel debugger and a conditional breakpoint.

    However, I would argue that you don’t really need this information; you need to make your app properly handle any message sent to it.

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