@Christian-Ehrlicher said in building qsqlmysql.dll for msvc error: Forgot to copy or typo? I forgot to copy. I looked into Makefile.Release and realised that instead of C:\mysql\include this It was including this C:\Program Files\MySQL\MySQL Server 8.0\include I deleted qmake.stash and config.cache and repeated the qmake again and this time I generated qsqlmysql.dll successfully. Tested it with Sample Cpp code in Qt, it's working. @Christian-Ehrlicher Thanks for the suggestion.

I haven't solved the problem yet, but I know what caused it. QtCreator is doing what it's supposed to, that is, finding the 5.15.1 libraries correctly. My problem is that my Cutelyst version was built with Qt 5.12.8. CMake automatically found and used the Qt 5.12.8 libraries I have installed, which allowed the version built with only CMake to run correctly. So, I built a Cutelyst version manually using the 5.15.1 libraries instead. I'm having trouble getting CMake to detect that version, but that's a separate issue, so I'll close this one.

Okay, I had absolutely believed that I had tried making the call to my savePos() function to try to diagnose whether the signal had something to do with it, yet when I disable the connect()ion altogether and call it explicitly, now these APIs want to behave like good little children and do what they're supposed to. So, essentially I shot myself in the foot by handling this with modelAboutToBeReset(), which implicitly trashes the internal cache of visible indexes. D'oh! Argh, etc. Thanks for the help, folks.

@Touchoco Glad it works, but it's a shame to have to change over to 32-bit Qt app just to be able to talk ODBC to Excel. If you want to pursue this further I think it is a non-Qt issue. You would have to Google for something about how to ODBC from a 64-bit executable when I have such-and-such (probably 32-bit) Excel, or similar.