What /u/FishInABarrel@kbin.social mentioned - that’s correct. But to elaborate: The icon image isn’t simply stored as an image, but kinda complex (out of scope to explain the whole concept, but you can read more about it here

What windows does the first time it comes across a new .exe, is extract the image, because this is an “expensive” process, it’s optimized to not do this every time, and instead the extracted image is dumped into C:\Users\%username%\AppData\Local\Microsoft\Windows\Explorer in one of the iconcache.db files.

When you recompile an exe with the same name but will a new icon, it will actually have a new icon, it’s just not shown, because the old icon is retrieved from the iconcache.db. You can get around this by deleting all your iconcache.db files

I also need something in case I make everything “from scratch”, like just compiling something from the command line.

Also, even if you compile from the console, you can usually still specify an icon on compile time, and don’t really have to inject it later after compiling. But of course that depends on the language / compiler on how you’d have to do that

If you export it “wrong” once, you have to change the generated exe name, or windows will refuse to use the new icon.

Sounds like you just need to clear the icon cache. It’s been a minute since I’ve written Windows apps, so I don’t remember that process, but I’m sure google could help you out.

Yea mate, that’s a cache problem of the local system… You should’ve just asked that question in the first place.

Btw I don’t know how this works on newer Windows (probably worse), but on older versions you just needed to view the properties of the exe to view its actual icon, and refresh the desktop or explorer window. On even older Windows 9x, my trick was to switch from 32b to 16b color bit depth and back to refresh the icons.