Yeah, common problem, no known solution.

more details, discussion or a bug report available?

It happens to me too in VS2017, basically with any breakpoint my system drops to about 1/3 fps and most keypresses / clicks / mouse movement will be dropped. Kinda just have to rapidly tap SHIFT+F5 until it manages to resume. (Actually did a little bit of debugging like this, but it was extremely frustrating and afterwards I switched to "printf debugging" instead.)

Seems to happen in GDB to with MinGW/MSYS to a lesser extent, but after the initial "slideshow" moment after hitting a breakpoint if I switch some windows around it seems to recover and I can step normally in GDB, so at least that's usable.

Has this been a problem for a long time? Does it affect other platforms or only windows?

For what its worth, it appears to be caused by the DirectInput code in the SDL library. Commenting out these lines fixes the issue (but causes other issues since the inputs aren't being processed):

1	/* Initialize DirectInput */
2	if ( DX5_DInputInit(this) < 0 ) {
3		return(-1);
4	}

Related discussion that seems to support my observation: https://stackoverflow.com/questions/17886883/ … while-debugging

I don't know if it's fixed in a newer version of SDL, or if there's a non-breaking change/configuration that could be applied to work around the issue.

In that case, perhaps setting SDL_VIDEODRIVER=WINDIB in environment variables before executing DOSBox can help.

Setting SDL_VIDEODRIVER=windib works for gdb for debugging DOSBox as long as it is not interfering with the feature you plan to debug on. I have been exclusively using gdb for debugging for years. My VS experience has been fading and I think the last version I used was VS2003 and thereafter never bothered for any new version of VS anymore. DOSBox was the reason back then that made me look into GCC seriously, a path that I have never looked back since then, even after Microsoft has eventually released Visual Studio for free.

I can confirm that this fixes the issue for VS debugging. Open Solution Properties (All Configurations) -> Debugging -> Environment -> Edit ...
Then add the line: sdl_videodriver=windib

I'd would be good if someone could update the build VS build instructions to make this more visible: https://www.dosbox.com/wiki/Building_DOSBox_w … h_Visual_Studio
I would but I don't have any permissions for the wiki. Also, the build steps for pdcurses is missing for VS. It turned out to be pretty easy but would be nice to add too.

I think the wiki has been locked for a while. When I revised that page I couldn't find a usable version of pdcurses, so it'd be nice to have some instruction there.

Ultimately though after writing that guide I installed MinGW and built it with that, and had a much easier time than trying to do it with Visual Studio.

Please update the wiki or at least stick this thread to the top. Making original DosBox to build is painful enough to struggle with this issue when you finally make debugging to run.