'Find a free interrupt slot
Some joker (BIOS/DOS/TSR...) has written random data in the Interrupt Vector Table. I know this because disassembling told me so.
Ordinarily before seizing an interrupt vector, I verify that the selected IVT slot is empty. But with all this left-behind-data, how can an humble application know that it is nonetheless safe to hook a particular interrupt vector?
Although my programmer's reference describes the DOS function 25h SetInterruptVector as
"Safely modifies an interrupt vector to point to a specified interrupt handler"
I don't think it cares too much about this pre-existing bogus content. So far for safely!
Is there some ingenious way to be absolutely sure that an interrupt vector is free?
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