Opening a can of worms here. But leaving all pitfalls aside.

If one wanted to write to the VMT of a class, would that be possible? Would the VMT be stored in write-able memory, once the exe is loaded?

Thanks

Martin Frb wrote

Opening a can of worms here. But leaving all pitfalls aside. If one wanted to write to the VMT of a class, would that be possible? Would the VMT be stored in write-able memory, once the exe is loaded?

It depends on the platforms. Most platforms support read-only relocatable memory, so they can make it permanently read-only after the (dynamic) linker has relocated everything. I don't know which ones do/don't.

Jonas

The mORMot[1] sources could give you some info.
During runtime, it patches the exe-memory to redirect function calls. Hard part was to get around the W^X memory protection on some BSD's.

Look at:

procedure PatchCode(Old,New: pointer; Size: integer; Backup: pointer;
inside SynCommons.pas
function TInterfaceFactory.GetMethodsVirtualTable: pointer;
inside mORMot.pas

Please don't use that kind of hacks. It also breaks in case WPO is used and some calls get devirtualised at compile time.

Jonas

This is mORMot. It consists solely of hacks :)

Michael.