DOS/16M FAQ:
Debugging

1. Under plain DOS, Instant-D tells me the selector at which d16LoadEXP() loaded the program. Under Windows, however, because the Windows VMM loads the program, I don't get that information. How do I know at what selector I should merge the symbols for the overloaded program?
2. I'm trying to use Instant-D performance monitor from within a Windows DOS box and I'm getting an error, 'interloper on PM int 70', when I type 'sam on'. Why?
3. When I attempt to load symbols into Instant-D, the MERGESYM command tells me I have no storage for source, yet the LIM command says there is over 1 MB left for source. What's going on?
4. How can I debug the real-mode interrupt handler part of a bimodal interrupt handler?

1. Under plain DOS, Instant-D tells me the selector at which d16LoadEXP() loaded the program. Under Windows, however, because the Windows VMM loads the program, I don't get that information. How do I know at what selector I should merge the symbols for the overloaded program?

Under DPMI you can look at DX:AX after the LoadEXP call, but a better way is to look at tsf.si. See the documentation for d16LoadEXP() for more information.

2. I'm trying to use Instant-D performance monitor from within a Windows DOS box and I'm getting an error, 'interloper on PM int 70', when I type 'sam on'. Why?

Sorry, the monitor function is not available under DPMI because of the way interrupts are managed.

3. When I attempt to load symbols into Instant-D, the MERGESYM command tells me I have no storage for source, yet the LIM command says there is over 1 MB left for source. What's going on?

You probably are trying to load too many symbols. If you are using the /Zi compiler switch, try /Zd instead, and use the SYM command instead of MERGESYM.

4. How can I debug the real-mode interrupt handler part of a bimodal interrupt handler?

We recommend that you install the real-mode handler, embed an INT 3 at the start of the handler, and run the program under CodeView. CodeView should break when the handler is called and allow normal debugging from that point on.